Correspondence to: J. Kevin Foskett, Department of Physiology, B400 Richards Building, University of Pennsylvania, Philadelphia, PA 19104-6085. Fax:(215) 573-6808 E-mail:foskett{at}mail.med.upenn.edu.
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Abstract |
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The inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R) is an endoplasmic reticulumlocalized Ca2+-release channel that controls complex cytoplasmic Ca2+ signaling in many cell types. At least three InsP3Rs encoded by different genes have been identified in mammalian cells, with different primary sequences, subcellular locations, variable ratios of expression, and heteromultimer formation. To examine regulation of channel gating of the type 3 isoform, recombinant rat type 3 InsP3R (r-InsP3R-3) was expressed in Xenopus oocytes, and single-channel recordings were obtained by patch-clamp electrophysiology of the outer nuclear membrane. Gating of the r-InsP3R-3 exhibited a biphasic dependence on cytoplasmic free Ca2+ concentration ([Ca2+]i). In the presence of 0.5 mM cytoplasmic free ATP, r-InsP3R-3 gating was inhibited by high [Ca2+]i with features similar to those of the endogenous Xenopus type 1 InsP3R (X-InsP3R-1). Ca2+ inhibition of channel gating had an inhibitory Hill coefficient of 3 and half-maximal inhibiting [Ca2+]i (Kinh) = 39 µM under saturating (10 µM) cytoplasmic InsP3 concentrations ([InsP3]). At [InsP3] < 100 nM, the r-InsP3R-3 became more sensitive to Ca2+ inhibition, with the InsP3 concentration dependence of Kinh described by a half-maximal [InsP3] of 55 nM and a Hill coefficient of
4. InsP3 activated the type 3 channel by tuning the efficacy of Ca2+ to inhibit it, by a mechanism similar to that observed for the type 1 isoform. In contrast, the r-InsP3R-3 channel was uniquely distinguished from the X-InsP3R-1 channel by its enhanced Ca2+ sensitivity of activation (half-maximal activating [Ca2+]i of 77 nM instead of 190 nM) and lack of cooperativity between Ca2+ activation sites (activating Hill coefficient of 1 instead of 2). These differences endow the InsP3R-3 with high gain InsP3induced Ca2+ release and low gain Ca2+induced Ca2+ release properties complementary to those of InsP3R-1. Thus, distinct Ca2+ signals may be conferred by complementary Ca2+ activation properties of different InsP3R isoforms.
Key Words: single-channel electrophysiology, patch-clamp, Xenopus oocyte, nucleus, Ca2+ release channel
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INTRODUCTION |
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Modulation of cytoplasmic free Ca2+ concentration ([Ca2+]i) in response to the second messenger inositol 1,4,5-trisphosphate (InsP3)1 provides a ubiquitous signaling system. InsP3-mediated Ca2+ signals are often complex, being precisely controlled in both time and space as repetitive spikes or oscillations and as propagating waves that initiate at specific locations in the cell (2,700 amino acid integral membrane proteins (
The diversity of InsP3R expression in mammalian cells is impressive, suggesting that cells require distinct InsP3Rs to provide unique Ca2+ signals and to regulate specific functions. Nevertheless, the functional correlates and physiological implications of this diversity are still unclear. Electrophysiological observations of all three isoforms have now been reported. The single-channel properties of the type 1 InsP3R have been examined by reconstitution of mammalian channels in lipid bilayer membranes (
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MATERIALS AND METHODS |
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Selection and Microinjection of Xenopus Oocytes
Maintenance of Xenopus laevis and surgical extraction of ovaries were carried out as described previously (
Oocytes selected for microinjection were defolliculated as described previously (
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Patch-clamp studies were performed 45 d after cRNA microinjection. The mean number of InsP3R per nuclear patch for the cRNA-injected oocytes increased dramatically by 47-fold, from 0.038 to 1.80. In 1,020 experiments, 1,831 channels were detected in 518 patches, with 354 of the patches exhibiting multiple InsP3R channels. If we assume a random, binomial association of X-InsP3R-1 and r-InsP3R-3 to form tetrameric channels, most (91.8%) of the channels detected in cRNA-injected oocytes were homotetrameric r-InsP3R-3 channels. This value probably underestimates the percentage of homotetrameric r-InsP3R-3 channels because of the higher probability of heterologously expressed channels to associate with other heterologously expressed channel monomers during protein biogenesis rather than with endogenous channels, due to the pronounced mismatch of the protein translation rates of expressed versus endogenous channels (
Patch-clamping the Oocyte Nucleus
Patch-clamp experiments were performed as described (2 min). Thus, experiments were done in the "on-nucleus" configuration, with the solution in the perinuclear lumen between the outer and inner nuclear membranes in apparent equilibrium with the bath solution (
Analyses of Patch-clamp Current Traces
The patch-clamp current traces were analyzed using MacTac software (Bruxton) to identify channel opening and closing events using a 50% threshold (, the mean dwell time of highest channel current level is
/n (Equation 1). If T is the minimum duration of an open event that is detectable in the experimental system, i.e., only events with duration longer than T will have amplitudes greater than the 50% threshold after filtering, then the rate of detection of the highest current level:
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(1) |
In our patch-clamp set up, T was empirically determined to be 0.2 ms using test pulses of variable duration. of InsP3R channels is
315 ms over the range of experimental conditions used. In experimental conditions with Po > 0.1, only current records with longer than 10 s of InsP3R channel activities were used. 10 s >> 1/R3, so there is little uncertainty in the number of channels in the current traces used. In experimental conditions with Po < 0.1, only current records exhibiting one open channel current level with record duration >5/R2 were used, to ensure that they were truly single-channel records.
Multiple conductance states were observed for recombinant r-InsP3R-3 (
Solutions for Patch-clamp Experiments
All patch-clamp experiments were performed with pipet solutions containing 140 mM KCl, 10 mM HEPES, and 0.5 mM Na2ATP, pH adjusted to 7.1 with KOH. By using K+ as the current carrier and appropriate quantities of the high affinity Ca2+ chelator, BAPTA (1,2-bis(O-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid [100500 µM]; Molecular Probes), or the low affinity Ca2+ chelator, 5,5'-dibromo BAPTA (100160 µM; Molecular Probes), or ATP (0.5 mM) alone to buffer Ca2+ in the experimental solutions, Ca2+ concentration was tightly controlled in our experiments. Total Ca2+ content (64306 µM) in the solutions was determined by induction-coupled plasma mass spectrometry (Mayo Medical Laboratory). Free [Ca2+] were calculated using the Maxchelator software (C. Patton, Stanford University, Stanford, CA). The free [Ca2+] of all solutions was also directly measured, using Ca2+-selective minielectrodes (
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RESULTS |
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Ca2+ Dependence of the Kinetic Properties of r-InsP3R-3 Gating
Gating of the InsP3R is sensitive to [Ca2+]i as well as [InsP3] (
To examine specifically the effects of [Ca2+]i on r-InsP3R-3 channel gating, a functionally saturating concentration of InsP3 (10 µM) was applied to the cytoplasmic (pipet) side of the channel to stimulate it fully at all experimental [Ca2+]i (Fig 2). At [Ca2+]i corresponding to resting levels in cells (10100 nM), the Po of the r-InsP3R-3 channel was moderate (<0.5; Fig 4), with the channel evidently active (Fig 2 A). The Po increased to 0.8 when [Ca2+]i was raised from 100 nM to 1 µM, which was associated with decreasing mean closed duration (
c) (Fig 3 and Fig 4). Between [Ca2+]i of 1 and 25 µM, Po remained high (
0.8; Fig 3 and Fig 4), with the channel exhibiting long sustained bursts of activities lasting up to several seconds, during which it only closed briefly (Fig 2 C). As [Ca2+]i was increased beyond 25 µM, Po dropped precipitously, as a result of an increase in
c to >200 ms (Fig 3 and Fig 4). Within the more than three orders of magnitude range of [Ca2+]i examined (24.7 nM82.8 µM), the mean open duration (
o) of the r-InsP3R-3 channel lay within a narrow range (416 ms) with no systematic dependence on [Ca2+]i (Fig 3 A). In contrast,
c changed about two orders of magnitude (from 3 to 210 ms; Fig 3 B) over the same range of [Ca2+]i, accounting for most of the strong dependence of channel Po on [Ca2+]i (Fig 4).
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Detailed analyses of the r-InsP3R-3 channel dwell time histograms revealed that the channel has at least two distinguishable open kinetic states (Fig 5): a long kinetic state with time constant () of
8 ms and a short kinetic state with
1 ms. The relative weight of the short kinetic state decreased as the channel was activated by increasing [Ca2+]i, and then increased as high [Ca2+]i inhibited channel activity. The channel closed dwell time histograms revealed at least three distinguishable closed kinetic states (Fig 5): (1) a long state with
> 10 ms; (2) a medium state with 3.5 ms <
< 10 ms; and (3) a short kinetic state with
< 1 ms. The decrease in
c and, therefore, increase in channel Po, as the channel was activated by increases in [Ca2+]i, was achieved by both a decrease in the relative weights and the time constants of the long and medium closed kinetic states. Reversal of this trend increased
c and decreased Po when the channel was inhibited by [Ca2+]i > 25 µM (Fig 5 D).
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The r-InsP3R-3 Po versus [Ca2+]i response in 10 µM InsP3 could be well fitted to a biphasic Hill equation (Fig 4) so that:
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(2) |
This suggests that the tetrameric InsP3R-3 channel can achieve a maximum open probability Pmax of 0.80 ± 0.03, with two distinct types of functional Ca2+ binding sites: activating sites with a half-maximal activating [Ca2+]i, Kact, of 77 ± 10 nM and a Hill coefficient Hact of 1.0 ± 0.1; and inhibitory sites with half-maximal inhibitory [Ca2+]i, Kinh, of 39 ± 7 µM and Hill coefficient Hinh of 2.8 ± 0.4. The Hill coefficient Hact of 1 indicates that Ca2+ activation of the InsP3R-3 is not cooperative under our experimental conditions, whereas the large Hill coefficient Hinh of 2.8 indicates that inhibition of the InsP3R by Ca2+ is a highly cooperative process.
InsP3 Sensitivity of the Ca2+ Dependence of r-InsP3R-3
The Ca2+ dependence of the gating of the X-InsP3R-1 is regulated by [InsP3] (
These data can be described by a simple model similar to one derived for the X-InsP3R-1 (
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(3) |
The results imply that the InsP3R has a single class of functional InsP3 binding sites with a half-maximal activating [InsP3], KIP3, of 55 ± 6 nM, a Hill coefficient HIP3 of 4.5 ± 1, and a maximum half-maximal inhibitory [Ca2+]i, K, of 39 ± 7 µM at saturating [InsP3]. The large Hill coefficient HIP3 of
4 indicates that InsP3 activation of the InsP3R is highly cooperative, requiring InsP3 binding to perhaps all four monomers of the channel to relieve the Ca2+ inhibition and gate the channel open.
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DISCUSSION |
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We recently described the first functional expression of the r-InsP3R-3, and examined its detailed permeation properties by patch-clamp electrophysiology of single channels in the Xenopus oocyte outer nuclear membrane (
Gating Properties and Ca2+ Inhibition of the r-InsP3R-3 and X-InsP3R-1 Channels Are Similar
Our results indicate that many gating properties of the main conductance state M of the X-InsP3R-1 and r-InsP3R-3 channels are similar in their responses to [Ca2+]i. Both channels have a Pmax of 0.8. Like the X-InsP3R-1 channel, the r-InsP3R-3 channel displays two distinct types of functional Ca2+ binding sites: (1) activating sites whose properties and their implications will be discussed in detail below; and (2) inhibitory sites, which have similar Kinh (54 ± 3 µM for X-InsP3R-1 and 39 ± 7 µM for r-InsP3R-3) and Hinh (3.9 ± 0.7 for X-InsP3R-1 and 2.8 ± 0.4 for r-InsP3R-3) in 10 µM InsP3. In both channels, the mean open channel durations remain within a narrow range (316 ms) over the whole range of [Ca2+]i examined. Thus, Ca2+-induced changes in Po of both channels were mainly due to large changes in the mean closed channel durations, which decreased as the channels became activated, and increased as Po decreased due to inhibition by high [Ca2+]i (Fig 3;
Our results indicate that the recombinant r-InsP3R-3, when expressed and recorded in the oocyte outer nuclear membrane, exhibits inhibition of channel activity by high [Ca2+]i. This behavior agrees with that observed in recent studies demonstrating a biphasic dependence on [Ca2+]i of type 3 InsP3R activities measured by either 45Ca2+ efflux from loaded Ca2+ stores in permeabilized cells16HBE14o- bronchial mucosal cells in 1 µM) than we observed in our single-channel patch-clamp experiments (Fig 4). The discrepancy between the results from cell-based assays and our single-channel measurements might possibly be explained by the difficulty in attaining sufficient control of the concentrations of InsP3 and Ca2+ in the microdomains around the InsP3R in the Ca2+ flux measurements. InsP3 concentrations used in the flux experiments200 nM in
55 nM), they might not be sufficient to ensure that the [InsP3] in the microenvironment around the InsP3R was saturating. Because InsP3 activates the channel by decreasing the sensitivity to Ca2+ inhibition (this study), Ca2+ release responses observed in the presence of a subsaturating concentration of InsP3 will be predicted to be associated with a lower half-maximal inhibitory [Ca2+]i, as observed in those studies. Alternately, there may be factors in the permeabilized cells and isolated microsomal vesicles associated with the InsP3R, for example phosphatidylinositol 4,5-bisphosphate (PIP2;
These observations of biphasic Ca2+ dependence of the type 3 InsP3R are in contrast with observations in another recent study (
It has been suggested (
InsP3 Activates the r-InsP3R-3 Channel by Tuning Ca2+ Inhibition
All the observed gating properties of the r-InsP3R-3 channel over wide ranges of [InsP3] and [Ca2+]i could be well fitted with a biphasic Hill equation with the half-maximal inhibitory [Ca2+]i, Kinh, being the only InsP3 concentration-sensitive parameter. Thus, the effect of InsP3 binding is not to enable activation of the r-InsP3R-3 by Ca2+, as expected for coagonist ligands and which has been generally assumed (4, indicating that this process of InsP3 activation of InsP3R channel activity is highly cooperative (
Analysis of the effects of InsP3 on channel gating indicates that the functional half-maximal activating [InsP3], KIP3, of the r-InsP3R-3 is 55 nM. A similar analysis for the X-InsP3R-1 indicated that KIP3
50 nM (
58 nM (
2200 nM;
2 nM) inactive state and low affinity (2060 nM) active state (
4, suggesting a general requirement for all four monomers in a tetramer to bind InsP3.
These functional and binding affinities of the various InsP3R isoforms for InsP3 (50 nM) are very different from the functional InsP3 EC50 of 3.2 µM reported in a recent study of the regulation by InsP3 of the type 3 InsP3R reconstituted into lipid bilayers (in 160 nM Ca2+;
The analyses of the kinetics of channel gating and the responses to InsP3 for both the types 1 and 3 InsP3R channels studied in native ER membrane now suggest a unifying model for channel activation by InsP3. Because [Ca2+]i affects the gating of the InsP3R primarily by regulating the closed state duration, and InsP3 regulates gating by tuning the channel sensitivity to Ca2+ inhibition, it follows that the kinetic basis for channel activation by InsP3 is the destabilization of the closed kinetic state(s). Consequently, InsP3 activates Ca2+ signaling by increasing the frequency of relatively stereotypic channel openings of (on average) 10 ms, each of which is the fundamental Ca2+ release event in Ca2+ signaling. InsP3 enhances the frequency of fundamental release events by reducing the Ca2+ affinity of the inhibitory binding site of the monomer to which it binds, in a process that is highly cooperative.
Ca2+ Activation of the r-InsP3R-3
The activating Ca2+ binding sites of the r-InsP3R-3 had a half-maximal activating [Ca2+]i, Kact, of 77 nM and Hact of 1. These values contrast markedly with those obtained for the X-InsP3R-1 (
210 nM and Hact
2 (Fig 6). Thus, in addition to a higher intrinsic sensitivity of the activating sites for Ca2+, the type 3 receptor lacks the apparent cooperativity among these sites that is observed in the type 1 receptor. This result agrees well with the flatter Ca2+ dependence of InsP3-induced Ca2+ release observed in B cells genetically engineered to express only InsP3R-3 compared with that observed in cells expressing InsP3R-1 only (
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The differences in the Ca2+ dependencies of the activation of the types 1 and 3 InsP3R are reflected in the dwell time distributions of the two isoforms at activating [Ca2+]i (<1 µM). Whereas the relative weight of the long open state (
8 ms) of both type 1 and type 3 InsP3R channels increased with [Ca2+]i during activation, most of the change in Po was the result of changes in the closed channel dwell time distribution. When [Ca2+]i was raised from 30 to 224 nM, there was a much more dramatic change in the closed channel dwell time distribution of the X-InsP3R-1 channel compared with that of the r-InsP3R-3 channel (Fig 5 and Fig 7). The rise in [Ca2+]i caused the predominant long closed state (
> 10 ms), as well as the longest closed state (
> 100 ms), of the X-InsP3R-1 channel to disappear (Fig 7), resulting in the steep increase in channel Po with Hact
2. In contrast, the long closed state (
> 10 ms) of the r-InsP3R-3 had a low relative weight in 31 nM Ca2+, giving the channel a lower Kact compared with the X-InsP3R-1. The disappearance of the long closed state with the rise in [Ca2+]i only caused a gentle increase in channel Po with Hact
1.
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Importantly, both the lower Kact and lack of cooperativity confer upon the type 3 channel the ability to remain active even at low [Ca2+]i (<100 nM) when stimulated by InsP3, where the type 1 receptor would be nearly quiescent (Fig 6). For example, at [Ca2+]i 50 nM, a resting level measured in many cell types, the Po of the type 3 channel in the presence of low concentrations of InsP3 (10 nM say) is
0.3, whereas the type 1 channel Po is nearly 10-fold lower (Fig 6). At
25 nM Ca2+, gating of the type 3 receptor is relatively robust (Po
0.2), whereas type 1 channel activities can hardly be detected (Fig 6).
Physiological Significance of Different Ca2+ Activation Properties of InsP3R-1 and InsP3R-3
The distinct properties of the Ca2+ activation sites of the InsP3R isoforms are likely to be of important physiological significance. Ca2+ released by the type 3 channel will serve to trigger release from other type 3 channels in a process of CICR. However, the results of our study now demonstrate that the type 3 receptor is designed to respond with only a limited dynamic range of CICR at resting [Ca2+]i (50 nM) and moderate stimulation ([InsP3] > 20 nM), as CICR can increase the frequency of fundamental release events by only 2.6-fold (Po increases from
0.3 at resting [Ca2+]i to a maximum of
0.8). The narrow dynamic range of CICR in the type 3 receptor is a consequence of its relatively robust channel activity at resting [Ca2+]i, which in turn derives from the high affinity of its Ca2+ activation sites, as well as their lack of cooperativity. In contrast, the type 3 receptor is poised to respond to low levels of stimulation that would be insufficient to activate the type 1 receptor. The same properties that confer the type 3 receptor with a low gain CICR, confer on it an exquisite sensitivity to weak stimuli at resting [Ca2+]i, as its Ca2+ release activity can increase from Po
0 to Po
0.3 when [InsP3] rises from 0 to <10 nM. Thus, in response to weak stimuli, i.e., low levels of InsP3, the InsP3R-3 behaves as a "switch", imparting high gain to InsP3-induced Ca2+ release (IICR).
Although there is little difference in the functional InsP3 sensitivities of the types 1 and 3 InsP3Rs, their differential Ca2+ activation properties result in an apparent higher InsP3 sensitivity in vivo of the type 3 release channel under conditions of resting levels of Ca2+ in the cytoplasm. The high gain IICR property of the type 3 receptor will enable it to provide a "trigger" release of Ca2+ that could recruit other release channel types. In contrast, the type 1 receptor is relatively insensitive to low levels of InsP3 at resting [Ca2+]i (low gain IICR). However, it is well designed to provide a wide dynamic range of Ca2+ release activity at resting [Ca2+]i (50 nM) and moderate stimulation ([InsP3] > 20 nM) by CICR, which can increase the frequency of fundamental release events by 20-fold (Po increases from 0.05 to 0.8 as [Ca2+]i increases from 50 to 1,000 nM) (Fig 6). Thus, the type 1 channel displays high gain CICR and low gain IICR. Because this behavior is complementary to the behavior of the type 3 channel, the presence of the two channels would be predicted to confer a distinct "[Ca2+]i repertoire" in response to stimulation, in contrast to the behaviors expected if either was the sole expressed isoform.
The efficacy of Ca2+ released through type 3 channels to trigger type 1 channel activity by CICR will depend on spatial proximity of the two channels and [InsP3], due to the limited range of Ca2+ diffusion in the cytoplasm. Functional X-InsP3R-1 and r-InsP3R-3 channels in the ER membrane have a high propensity to exist in clusters of up to 10 channels (
By regulating the affinity of the Ca2+ inhibition sites, the [InsP3] will also determine the efficacy of "cross-talk" from the type 3 to the type 1 receptor, as it defines the extent to which Ca2+ can be released. At low [InsP3] (<30 nM), CICR from the InsP3R-1 is limited by highly efficacious negative feedback by Ca2+. Because InsP3 binding to the InsP3R reduces Ca2+ inhibition of the channel, [Ca2+]i that can inhibit channel activity at low [InsP3] will be insufficient to inhibit it when [InsP3] is increased. In addition to enabling graded Ca2+ release from InsP3-sensitive stores, this mechanism enables more intense stimuli to promote greater diffusive spread of the local Ca2+ signal to other sites.
In summary, our results indicate that the types 1 and 3 InsP3R isoforms are functionally similar in terms of their permeation and gating properties, regulation by InsP3, and inhibition by cytoplasmic Ca2+. However, the isoforms are uniquely distinguished by their sensitivities to activation by Ca2+. Differential Ca2+ sensitivity of Ca2+ activation sites confers on each InsP3R isoform distinct and complementary release properties in response to cellular stimulation. The relative expression level and spatial localization of different InsP3R types will enable these properties to interact to generate complex Ca2+ signals, including graded release, oscillations, and waves.
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Footnotes |
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1 Abbreviations used in this paper: CICR, Ca2+-induced Ca2+ release; InsP3, inositol 1,4,5-trisphosphate; ER, endoplasmic reticulum; IICR, InsP3-induced Ca2+ release; PIP2, phosphatidylinositol 4,5-bisphosphate; Po, open probability; r-InsP3R-3, rat type 3 InsP3R; X-InsP3R-1, Xenopus type 1 InsP3R.
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Acknowledgements |
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We thank Dr. Graeme Bell (University of Chicago, Chicago, IL) for providing r-InsP3R-3 cDNA, and Dr. Suresh Joseph (Thomas Jefferson University) for InsP3R antibodies.
This work was supported by grants to J.K. Foskett from the National Institutes of Health (MH59937 and GM56328) and to D.-O.D. Mak from the American Heart Association (9906220U).
Submitted: 19 January 2001
Revised: 15 March 2001
Accepted: 19 March 2001
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References |
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Atri, A., Amundson, J., Clapham, D., and Sneyd, J. 1993. A single-pool model for intracellular calcium oscillations and waves in the Xenopus laevis oocyte. Biophys. J. 65:1727-1739[Abstract].
Baudet, S.B., Hove-Madsen, L., and Bers, D.M. 1994. How to make and use calcium-specific mini- and microelectrodes. In Nuccitelli R., ed. A Practical Guide to the Study of Calcium in Living Cells. San Diego, CA, Academic Press Inc, 94-114.
Benevolensky, D., Moraru, I.I., and Watras, J. 1994. Micromolar calcium decreases affinity of inositol trisphosphate receptor in vascular smooth muscle. Biochem. J. 299:631-636[Medline].
Berridge, M.J. 1993. Inositol trisphosphate and calcium signalling. Nature. 361:315-325[Medline].
Bezprozvanny, I., and Ehrlich, B.E. 1994. Inositol (1,4,5)-trisphosphate (InsP3)-gated Ca channels from cerebellum: conduction properties for divalent cations and regulation by intraluminal calcium. J. Gen. Physiol. 104:821-856[Abstract].
Bezprozvanny, I., and Ehrlich, B.E. 1995. The inositol 1,4,5-trisphosphate (InsP3) receptor. J. Membr. Biol. 145:205-216[Medline].
Bezprozvanny, I., Watras, J., and Ehrlich, B.E. 1991. Bell-shaped calcium-response curves of Ins(1,4,5)P3- and calcium-gated channels from endoplasmic reticulum of cerebellum. Nature. 351:751-754[Medline].
Bezprozvanny, I., Bezprozvannaya, S., and Ehrlich, B.E. 1994. Caffeine-induced inhibition of inositol(1,4,5)-trisphosphate-gated calcium channels from cerebellum. Mol. Biol. Cell. 5:97-103[Abstract].
Blondel, O., Takeda, J., Janssen, H., Seino, S., and Bell, G.I. 1993. Sequence and functional characterization of a third inositol trisphosphate receptor subtype, IP3R-3, expressed in pancreatic islets, kidney, gastrointestinal tract, and other tissues. J. Biol. Chem. 268:11356-11363
Boehning, D., and Joseph, S.K. 2000. Functional properties of recombinant type I and type III inositol 1,4,5-trisphosphate receptor isoforms expressed in COS-7 cells. J. Biol. Chem. 275:21492-21499
Boitano, S., Dirksen, E.R., and Sanderson, M.J. 1992. Intercellular propagation of calcium waves mediated by inositol trisphosphate. Science. 258:292-295[Medline].
Bootman, M.D., and Berridge, M.J. 1995. The elemental principles of calcium signaling. Cell. 83:675-678[Medline].
Bush, K.T., Stuart, R.O., Li, S.-H., Moura, L.A., Sharp, A.H., Ross, C.A., and Nigam, S.K. 1994. Epithelial inositol 1,4,5-trisphosphate receptors. Multiplicity of localization, solubility, and isoforms. J. Biol. Chem. 269:23694-23699
Cardy, T.J.A., Traynor, D., and Taylor, C.W. 1997. Differential regulation of types-1 and -3 inositol trisphosphate receptors by cytosolic Ca2+. Biochem. J. 328:785-793[Medline].
Carter, T.D., and Ogden, D. 1997. Kinetics of Ca2+ release by InsP3 in pig single aortic endothelial cells: evidence for an inhibitory role of cytosolic Ca2+ in regulating hormonally evoked Ca2+ spikes. J. Physiol. 504:17-33[Abstract].
Clapham, D.E. 1995. Calcium signaling. Cell. 80:259-268[Medline].
Danoff, S.K., Ferris, C.D., Donath, C., Fischer, G., Munemitsu, S., Ullrich, S., Snyder, S.H., and Ross, C.A. 1991. Inositol 1,4,5-trisphosphate receptors: distinct neuronal and non-neuronal forms generated by alternative splicing differ in phosphorylation. Proc. Natl. Acad. Sci. USA. 88:2951-2955[Abstract].
De Smedt, H., Missiaen, L., Parys, J.B., Bootman, M.D., Mertens, L., Van den Bosch, L., and Casteels, R. 1994. Determination of relative amounts of inositol trisphosphate receptor mRNA isoforms by ratio polymerase chain reaction. J. Biol. Chem. 269:21691-21698
De Smedt, H., Missiaen, L., Parys, J.B., Henning, R.H., Sienaert, I., Vanlingen, S., Gijsens, A., Himpens, B., and Casteels, R. 1997. Isoform diversity of the inositol trisphosphate receptor in cell types of mouse origin. Biochem. J. 322:575-583[Medline].
Dufour, J.F., Arias, I.M., and Turner, T.J. 1997. Inositol 1,4,5-trisphosphate and calcium regulate the calcium channel function of the hepatic inositol 1,4,5-trisphosphate receptor. J. Biol. Chem. 272:2675-2681
Ferris, C.D., and Snyder, S.H. 1992. Inositol phosphate receptors and calcium disposition in the brain. J. Neurosci. 12:1567-1574[Medline].
Fujino, I., Yamada, N., Miyawaki, A., Hasegawa, M., Furuichi, T., and Mikoshiba, K. 1995. Differential expression of type 2 and type 3 inositol 1,4,5-trisphosphate receptor mRNAs in various mouse tissues: in situ hybridization study. Cell Tissue Res. 280:201-210[Medline].
Furuichi, T., and Mikoshiba, K. 1995. Inositol 1,4,5-trisphosphate receptor-mediated Ca2+ signaling in the brain. J. Neurochem. 64:953-960[Medline].
Furuichi, T., Yoshikawa, S., Miyawaki, A., Wada, K., Maeda, N., and Mikoshiba, K. 1989. Primary structure and functional expression of the inositol 1,4,5-trisphosphate-binding protein P400. Nature. 342:32-38[Medline].
Furuichi, T., Kohda, K., Miyawaki, A., and Mikoshiba, K. 1994. Intracellular channels. Curr. Opin. Neurobiol. 4:294-303[Medline].
Hagar, R.E., and Ehrlich, B.E. 2000. Regulation of the type III InsP3 receptor by InsP3 and ATP. Biophys. J. 79:271-278
Hagar, R.E., Burgstahler, A.D., Nathanson, M.H., and Ehrlich, B.E. 1998. Type III InsP3 receptor channel stays open in the presence of increased calcium. Nature. 396:81-84[Medline].
Hingorani, S.R., and Agnew, W.S. 1992. Assay and purification of neuronal receptors for inositol 1,4,5-trisphosphate. Methods Enzymol. 207:573-591[Medline].
Hirota, J., Michikawa, T., Natsume, T., Furuichi, T., and Mikoshiba, K. 1999. Calmodulin inhibits inositol 1,4,5-trisphosphate-induced calcium release through the purified and reconstituted inositol 1,4,5-trisphosphate receptor type 1. FEBS Lett. 456:322-326[Medline].
Honda, Z., Takano, T., Hirose, N., Suzuki, T., Muto, A., Kume, S., Mikoshiba, K., Itoh, K., and Shimizu, T. 1995. Gq pathway desensitizes chemotactic receptor-induced calcium signaling via inositol trisphosphate receptor down-regulation. J. Biol. Chem. 270:4840-4844
Iino, M., and Tsukioka, M. 1994. Feedback control of inositol trisphosphate signalling by calcium. Mol. Cell. Endocrinol. 98:141-146[Medline].
Jiang, Q.S., Mak, D., Devidas, S., Schwiebert, E.M., Bragin, A., Zhang, Y., Skach, W.R., Guggino, W.B., Foskett, J.K., and Engelhardt, F. 1998. Cystic fibrosis transmembrane conductance regulatorassociated ATP release is controlled by a chloride sensor. J. Cell Biol. 143:645-657
Joseph, S.K., and Samanta, S. 1993. Detergent solubility of the inositol trisphosphate receptor in rat brain membranes. Evidence for association of the receptor with ankyrin. J. Biol. Chem. 268:6477-6486
Joseph, S.K. 1995. The inositol trisphosphate receptor family. Cell. Signalling. 8:1-7.
Joseph, S.K., Lin, C., Pierson, S., Thomas, A.P., and Maranto, A.R. 1995. Heteroligomers of type-I and type-III inositol trisphosphate receptors in WB rat liver epithelial cells. J. Biol. Chem. 270:23310-23316
Joseph, S.K., Bokkala, S., Boehning, D., and Zeigler, S. 2000. Factors determining the composition of inositol trisphosphate receptor hetero-oligomers expressed in COS cells. J. Biol. Chem. 275:16084-16090
Kaftan, E.J., Ehrlich, B.E., and Watras, J. 1997. Inositol 1,4,5-trisphosphate (InsP3) and calcium interact to increase the dynamic range of InsP3 receptor-dependent calcium signaling. J. Gen. Physiol. 110:529-538
Kasai, H., and Petersen, O.H. 1994. Spatial dynamics of second messengers: IP3 and cAMP as long-range and associative messengers. Trends Neurosci. 17:95-101[Medline].
Kume, S., Muto, A., Aruga, J., Nakagawa, T., Michikawa, T., Furuichi, T., Nakade, S., Okano, H., and Mikoshiba, K. 1993. The Xenopus IP3 receptor: structure, function, and localization in oocytes and eggs. Cell. 73:555-570[Medline].
Lechleiter, J.D., and Clapham, D.E. 1992. Molecular mechanisms of intracellular calcium excitability in X. laevis oocytes. Cell. 69:283-294[Medline].
Lee, M.G., Xu, X., Zeng, W.Z., Diaz, J., Wojcikiewicz, R.J.H., Kuo, T.H., Wuytack, F., Racymaekers, L., and Muallem, S. 1997. Polarized expression of Ca2+ channels in pancreatic and salivary gland cells. Correlation with initiation and propagation of [Ca2+]i waves. J. Biol. Chem. 272:15765-15770
Lupu, V.D., Kaznacheyeva, E., Krishna, U.M., Falck, J.R., and Bezprozvanny, I. 1998. Functional coupling of phosphatidylinositol 4,5-bisphosphate to inositol 1,4,5-trisphosphate receptor. J. Biol. Chem. 271:14067-14070
Maeda, N., Kawasaki, T., Nakade, S., Yokota, N., Taguchi, T., Kasai, M., and Mikoshiba, K. 1991. Structural and functional characterization of inositol 1,4,5-trisphosphate receptor channel from mouse cerebellum. J. Biol. Chem. 266:1109-1116
Magnusson, A., Haug, L.S., Walaas, S.I., and Ostvold, A.C. 1993. Calcium-induced degradation of the inositol (1,4,5)-trisphosphate receptor/Ca2+-channel. FEBS Lett. 323:229-232[Medline].
Mak, D.-O.D., and Foskett, J.K. 1994. Single-channel inositol 1,4,5-trisphosphate receptor currents revealed by patch clamp of isolated Xenopus oocyte nuclei. J. Biol. Chem. 269:29375-29378
Mak, D.-O.D., and Foskett, J.K. 1997. Single-channel kinetics, inactivation, and spatial distribution of inositol trisphosphate (IP3) receptors in Xenopus oocyte nucleus. J. Gen. Physiol. 109:571-587
Mak, D.-O.D, and Foskett, J.K. 1998. Effects of divalent cations on singlechannel conduction properties of Xenopus IP3 receptor. Am. J. Physiol. 275:C179-C188
Mak, D.-O.D., McBride, S., and Foskett, J.K. 1998. Inositol 1,4,5-trisphosphate activation of inositol trisphosphate receptor Ca2+ channel by ligand tuning of Ca2+ inhibition. Proc. Natl. Acad. Sci. USA. 95:15821-15825
Mak, D.-O.D., McBride, S., and Foskett, J.K. 1999. ATP regulation of type 1 inositol 1,4,5-trisphosphate receptor channel gating by allosteric tuning of Ca2+ activation. J. Biol. Chem. 274:22231-22237
Mak, D.-O.D., McBride, S., Raghuram, V., Yue, Y., Joseph, S.K., and Foskett, J.K. 2000. Single-channel properties in endoplasmic reticulum membrane of recombinant type 3 inositol trisphosphate receptor. J. Gen. Physiol. 115:241-255
Maranto, A.R. 1994. Primary structure, ligand binding, and localization of the human type 3 inositol 1,4,5-trisphosphate receptor expressed in intestinal epithelium. J. Biol. Chem. 269:1222-1230
Marshall, I.C.B., and Taylor, C.W. 1994. Two calcium-binding sites mediate the interconversion of liver inositol 1,4,5-trisphosphate receptors between three conformational states. Biochem. J. 301:591-598[Medline].
Mauger, J.-P., Lièvremont, J.-P., Piétri-Rouxel, F., Hilly, M., and Coquil, J.-F. 1994. The inositol 1,4,5-trisphosphate receptor: kinetic properties and regulation. Mol. Cell. Endocrinol. 98:133-139[Medline].
Meyer, T., Holowka, D., and Stryer, L. 1988. Highly Cooperative opening of calcium channels by inositol 1,4,5-trisphosphate. Science 240:653-655[Medline].
Michikawa, T., Hirota, J., Kawano, S., Hiraoka, M., Yamada, M., Furuichi, T., and Mikoshiba, K. 1999. Calmodulin mediates calcium-dependent inactivation of the cerebellar type 1 inositol 1,14,5-trisphosphate receptor. Neuron. 23:799-808[Medline].
Mignery, G.A., Sudhof, T.C., Takei, K., and De Camilli, P. 1989. Putative receptor for inositol 1,4,5-trisphosphate similar to ryanodine receptor. Nature. 342:192-195[Medline].
Missiaen, L., Parys, J.B., Sienaert, I., Maes, K., Kunzelmann, K., Takahashi, M., Tanzawa, K., and De Smedt, H. 1998. Functional properties of the type-3 InsP3 receptor in 16HBE14o- bronchial mucosal cells. J. Biol. Chem. 273:8983-8986
Missiaen, L., De Smedt, H., Bultynck, G., Vanlingen, S., De Smet, P., Callewaert, G., and Parys, J.B. 2000. Calmodulin increases the sensitivity of type 3 inositol-1,4,5-trisphosphate receptors to Ca2+ inhibition in human bronchial mucosal cells. Mol. Pharmacol. 57:564-567
Miyakawa, T., Maeda, A., Yamazawa, T., Hirose, K., Kurosake, T., and Iino, M. 1999. Encoding of Ca2+ signals by differential expression of IP3 receptor subtypes. EMBO (Eur. Mol. Biol. Organ.) J. 18:1303-1308
Monkawa, T., Miyawaki, A., Sugiyama, T., Yoneshima, H., Yamamoto-Hino, M., Furuichi, T., Saruta, T., Hasegawa, M., and Mikoshiba, K. 1995. Heterotetrameric complex formation of inositol 1,4,5-trisphosphate receptor subunits. J. Biol. Chem. 270:14700-14704
Monkawa, T., Hayashi, M., Miyawaki, A., Sugiyama, T., Yamamoto-Hino, M., Hasegawa, M., Furuichi, T., Mikoshiba, K., and Saruta, T. 1998. Localization of inositol 1,4,5-trisphosphate receptors in the rat kidney. Kidney Int. 53:296-301[Medline].
Nakagawa, T., Okano, H., Furuichi, T., Aruga, J., and Mikoshiba, K. 1991. The subtypes of the mouse inositol 1,4,5-trisphosphate receptor are expressed in a tissue-specific and developmentally-specific manner. Proc. Natl. Acad. Sci. USA. 88:6244-6248[Abstract].
Newton, C.L., Mignery, G.A., and Südhof, T.C. 1994. Co-expression in vertebrate tissues and cell lines of multiple inositol 1,4,5-trisphosphate (InsP3) receptors with distinct affinities for InsP3. J. Biol. Chem. 269:28613-28619
Nucifora, F.C., Jr., Sharp, A.H., Milgram, S.L., and Ross, C.A. 1996. Inositol 1,4,5-trisphosphate receptors in endocrine cells: localization and association in hetero- and homotetramers. Mol. Biol. Cell. 7:949-960[Abstract].
Parker, I., Choi, J., and Yao, Y. 1996. Elementary events of InsP3-induced Ca2+ liberation in Xenopus oocytes: hot spots, puffs and blips. Cell Calcium. 20:105-121[Medline].
Patel, S., Morris, S.A., Adkins, C.E., O'Beirne, G., and Taylor, C.W. 1997. Ca2+-independent inhibition of inositol trisphosphate receptors by calmodulin: redistribution of calmodulin as a possible means of regulating Ca2+ mobilization. Proc. Natl. Acad. Sci. USA. 94:11627-11632
Perez, P.J., Ramos-Franco, J., Fill, M., and Mignery, G.A. 1997. Identification and functional reconstitution of the type 2 inositol 1,4,5-trisphosphate receptor from ventricular cardiac myocytes. J. Biol. Chem. 272:23961-23969
Petersen, O.H. 1996. New aspects of cytosolic calcium signaling. News Physiol. Sci. 11:13-17
Putney, J.W., Jr., and St. J. Bird, G. 1993. The inositol phosphate-calcium signaling system in nonexcitable cells. Endocr. Rev. 14:610-631[Medline].
Ramos-Franco, J., Fill, M., and Mignery, G.A. 1998. Isoform-specific function of single inositol 1,4,5-trisphosphate receptor channels. Biophys. J. 75:834-839
Rooney, T.A., and Thomas, A.P. 1993. Intracellular calcium waves generated by Ins(1,4,5)P3-dependent mechanisms. Cell Calcium. 14:674-690[Medline].
Schrenzel, J., Demaurex, N., Foti, M., Van Delden, C., Jacquet, J., Mayr, G., Lew, D.P., and Krause, K.H. 1995. Highly cooperative Ca2+ elevations in response to ins(1,4,5)P3 microperfusion through a patch-clamp pipette. Biophys. J. 69:2378-2391[Abstract].
Sigworth, F.J., and Sine, S.M. 1987. Data transformations for improved display and fitting of single channel dwell time histograms. Biophys. J. 52:1047-1054[Abstract].
Stehno-Bittel, L., Lückhoff, A., and Clapham, D.E. 1995. Calcium release from the nucleus by InsP3 receptor channels. Neuron. 14:163-167[Medline].
Sudhof, T.C., Newton, C.L., Archer, B.T., Ushkaryov, Y.A., and Mignery, G.A. 1991. Structure of a novel InsP3-receptor. EMBO (Eur. Mol. Biol. Organ.) J. 10:3199-3206[Abstract].
Sugiyama, T., Furuya, A., Monkawa, T., Yamamoto-Hino, M., Satoh, S., Ohmori, K., Miyawaki, A., Hanai, N., Mikoshiba, K., and Hasegawa, M. 1994. Monoclonal antibodies distinctively recognizing the subtypes of inositol 1,4,5-trisphosphate receptor: application to the studies on inflammatory cells. FEBS Lett. 354:149-154[Medline].
Supattapone, S., Worley, P.F., Baraban, J.M., and Snyder, S.H. 1988. Solubilization, purification and isolation of an inositol trisphosphate receptor. J. Biol. Chem. 263:1530-1534
Swatton, J.E., Morris, S.A., Cardy, T.J.A., and Taylor, C.W. 1999. Type 3 inositol trisphosphate receptors in RINm5F cells are biphasically regulated by cytosolic Ca2+ and mediate quantal Ca2+ mobilization. Biochem. J. 344:55-60[Medline].
Taylor, C.W., and Richardson, A. 1991. Structure and function of inositol trisphosphate receptors. Pharmacol. Ther. 51:97-137[Medline].
Taylor, C.W., and Marshall, I.C.B. 1992. Calcium and inositol 1,4,5-trisphosphate receptors: a complex relationship. Trends Biochem. Sci. 17:403-407[Medline].
Taylor, C.W., and Traynor, D. 1995. Calcium and inositol trisphosphate receptors. J. Membr. Biol. 145:109-118[Medline].
Toescu, E.C. 1995. Temporal and spatial heterogeneities of Ca2+ signaling: mechanisms and physiological roles. Am. J. Physiol. 269:G173-G185
Watras, J., Bezprozvanny, I., and Ehrlich, B.E. 1991. Inositol 1,4,5-trisphosphate-gated channels in cerebellum: presence of multiple conductance states. J. Neurosci. 11:3239-3245[Abstract].
Welch, W., Williams, A.J., Tinker, A., Mitchell, K.E., Deslongchamps, P., Lamothe, J., Gerzon, K., Bidasee, K.R., Besch, H.R., Jr., and Airey, J.A. et al. 1997. Structural components of ryanodine responsible for modulation of sarcoplasmic reticulum calcium channel function. Biochemistry. 36:2939-2950[Medline].
Wojcikiewicz, R.J.H. 1995. Type I, II, and III inositol 1,4,5-trisphosphate receptors are unequally susceptible to down-regulation and are expressed in markedly different proportions in different cell types. J. Biol. Chem. 270:11678-11683
Wojcikiewicz, R.J.H., and He, Y. 1995. Type I, II and III inositol 1,4,5-trisphosphate receptor coimmunoprecipitation as evidence for the existence of heterotetrameric receptor complexes. Biochem. Biophys. Res. Commun. 213:334-341[Medline].
Wojcikiewicz, R.J.H., Furuichi, T., Nakade, S., Mikoshiba, K., and Nahorski, S.R. 1994. Muscarinic receptor activation down-regulates the type I inositol 1,4,5-trisphosphate receptor by accelerating its degradation. J. Biol. Chem. 269:7963-7969
Yamada, M., Miyawaki, A., Saito, K., Nakajima, T., Yamamoto-Hino, M., Ryo, Y., Furuichi, T., and Mikoshiba, K. 1995. The calmodulin-binding domain in the mouse type 1 inositol 1,4,5-trisphosphate receptor. Biochem. J. 308:83-88[Medline].
Yoneshima, H., Miyawaki, A., Michikawa, T., Furuichi, T., and Mikoshiba, K. 1997. Ca2+ differentially regulates the ligand-affinity states of type 1 and type 3 inositol 1,4,5-trisphosphate receptors. Biochem. J. 322:591-596[Medline].
Yule, D.I., Ernst, S.A., Ohnishi, H., and Wojcikiewicz, R.J.H. 1997. Evidence that zymogen granules are not a physiologically relevant calcium pool. Defining the distribution of inositol 1,4,5-trisphosphate receptors in pancreatic acinar cells. J. Biol. Chem. 272:9093-9098