Okadaic Acid Activates Atypical Protein Kinase C (
/
) in
Rat and 3T3/L1 Adipocytes
AN APPARENT REQUIREMENT FOR ACTIVATION OF GLUT4 TRANSLOCATION
AND GLUCOSE TRANSPORT*
M. L.
Standaert,
G.
Bandyopadhyay,
M. P.
Sajan,
L.
Cong,
M. J.
Quon
, and
R. V.
Farese§
From the J. A. Haley Veterans' Hospital Research Service and
Department of Internal Medicine, University of South Florida College of
Medicine, Tampa, Florida 33612 and
Hypertension-Endocrine
Branch, NHLBI, National Institutes of Health, Bethesda, Maryland
20892
 |
ABSTRACT |
Okadaic acid, an inhibitor of protein
phosphatases 1 and 2A, is known to provoke insulin-like effects on
GLUT4 translocation and glucose transport, but the underlying mechanism
is obscure. Presently, we found in both rat adipocytes and 3T3/L1
adipocytes that okadaic acid provoked partial insulin-like increases in
glucose transport, which were inhibited by phosphatidylinositol (PI)
3-kinase inhibitors, wortmannin and LY294002, and inhibitors of
atypical protein kinase C (PKC) isoforms,
and
. Moreover, in
both cell types, okadaic acid provoked increases in the activity of
immunoprecipitable PKC-
/
by a PI 3-kinase-dependent
mechanism. In keeping with apparent PI 3-kinase dependence of
stimulatory effects of okadaic acid on glucose transport and
PKC-
/
activity, okadaic acid provoked insulin-like increases in
membrane PI 3-kinase activity in rat adipocytes; the mechanism for PI
3-kinase activation was uncertain, however, because it was not apparent
in phosphotyrosine immunoprecipitates. Of further note, okadaic acid
provoked partial insulin-like increases in the translocation of
hemagglutinin antigen-tagged GLUT4 to the plasma membrane in
transiently transfected rat adipocytes, and these stimulatory effects
on hemagglutinin antigen-tagged GLUT4 translocation were inhibited by
co-expression of kinase-inactive forms of PKC-
and PKC-
but not
by a double mutant (T308A, S473A), activation-resistant form of protein
kinase B. Our findings suggest that, as with insulin, PI
3-kinase-dependent atypical PKCs,
and
, are required
for okadaic acid-induced increases in GLUT4 translocation and glucose
transport in rat adipocytes and 3T3/L1 adipocytes.
 |
INTRODUCTION |
Okadaic acid provokes insulin-like effects on the translocation of
the GLUT4 glucose transporter and glucose transport by mechanisms that
are presently obscure. In rat adipocytes, stimulatory effects of
okadaic acid on a process that is largely dependent on glucose
transport, viz. acute incorporation of labeled glucose into
lipids, are inhibited by the inhibitor of phosphatidylinositol (PI)1 3-kinase, wortmannin
(1), and are associated with activation of protein kinase B (PKB) (2),
which generally functions downstream of PI 3-kinase. These findings
therefore raised the possibility that okadaic acid, like insulin, may
activate PI 3-kinase and dependent processes, including PKB activation
and glucose transport, in the rat adipocyte. However, effects of
okadaic acid on PI 3-kinase and effects of PI 3-kinase inhibitors on
okadaic acid-stimulated glucose transport in rat adipocytes have not
been reported. In addition, in rat skeletal muscles (1) and human
adipocytes (3), stimulatory effects of okadaic acid on glucose
transport are wortmannin-insensitive and therefore appear to be largely independent of PI 3-kinase; moreover, in rat skeletal muscle (4), 3T3/L1 adipocytes (4), and human adipocytes (3), okadaic acid alone has
no effect on phosphotyrosine-associated PI 3-kinase activity, and, in
fact, inhibits insulin effects on this PI 3-kinase activity, apparently
via enhanced serine/threonine phosphorylation of insulin receptor
substrate-1 (IRS-1) (5). Accordingly, some findings suggest that
okadaic acid can activate glucose transport independently of PI
3-kinase.
To add to the confusion as to whether okadaic acid activates PI
3-kinase and/or PI 3-kinase-regulated processes in rat adipocytes, there is uncertainty as to what protein kinase(s) serves as a distal
activator of GLUT4 translocation and glucose transport during okadaic
action. In this regard, although PKB is activated by okadaic acid in
rat adipocytes and transient expression of a membrane-targeted
constitutively active PKB results in the activation of GLUT4
translocation in the rat adipocyte (6), it is uncertain if PKB is
required for effects of okadaic acid on GLUT4 translocation and glucose
transport. Indeed, in rat adipocytes, only a relatively small fraction
of insulin-stimulated GLUT4 translocation is inhibited by a
kinase-inactive (KI) form of PKB (6). Also, in 3T3/L1 adipocytes,
studies in which a double mutant (T308A,S473A), activation-resistant form of PKB was used as an effective dominant-negative inhibitor for
insulin-sensitive PKB-mediated processes (e.g. protein
synthesis) suggest that PKB is not required for insulin-stimulated
GLUT4 translocation and glucose transport (7).
With respect to other potential mechanisms for activating glucose
transport, PKC-
and PKC-
are activated by insulin through a PI
3-kinase-dependent mechanism (8), and effects of insulin on
GLUT4 translocation and glucose transport in rat adipocytes (8), 3T3/L1
adipocytes (9, 10), and L6 myotubes (11) appear to be dependent upon
the activation of one or both of these atypical PKCs. We therefore
examined the possibility that the effects of okadaic acid on glucose
transport and GLUT4 translocation in rat adipocytes and 3T3/L1
adipocytes may be mediated through the activation of PKC-
and/or
PKC-
.
 |
EXPERIMENTAL PROCEDURES |
Cell Preparations and Incubations--
As described (8), rat
adipocytes were prepared by collagenase digestion of epididymal fat
pads, equilibrated in glucose-free Krebs-Ringer phosphate medium
containing 1% bovine serum albumin with or without PKC-
/
inhibitors (cell-permeable myristoylated PKC-
/
pseudosubstrate
(myr-SIYRRGARRWRKL; Quality Controlled Biochemical, Hopkington, MA) or
RO 31-8220 (Alexis, San Diego, CA)) or PI 3-kinase inhibitors
(wortmannin (Sigma) or LY 294002 (Alexis)), and subsequently incubated,
as described in the text, with or without okadaic acid or insulin.
Similarly, as described by Bandyopadhyay et al. (9), 3T3/L1
adipocytes were differentiated, equilibrated, and incubated in
glucose-free Krebs-Ringer phosphate medium with the above described inhibitors and insulin or okadaic acid as described in the text.
2-[3H]Deoxyglucose (2-DOG) Uptake--
Rat
adipocytes were treated for 30 min with or without 10 nM
insulin or 1 µM okadaic acid, 0.1 mM 2-DOG
containing 0.1 µCi [3H]DOG (NEN Life Science Products)
was added, and uptake of 2-[3H]DOG over 1 min was
measured as described (8). 3T3/L1 adipocytes were incubated in the same
conditions, except that 100 nM insulin was used, and uptake
was measured over 5 min (see Ref. 9).
PKC-
/
Activation--
Activation of immunoprecipitable
PKC-
/
was determined as described (8, 9). In brief, after
incubation of intact cells with or without okadaic acid or insulin,
cells were homogenized and cell lysates (defatted, post-nuclear
homogenates in buffer containing 0.25 M sucrose, 20 mM Tris/HCl (pH 7.5), 1.2 mM EGTA, 20 mM
-mercaptoethanol, 1 mM
phenylmethylsulfonyl fluoride, 20 µg/ml leupeptin, 20 µg/ml
aprotinin, 1 mM Na3VO4, 1 mM Na4P2O7, 1 mM NaF, 0.15 M NaCl, 1% Triton X-100, and
0.5% Nonidet) were subjected to immunoprecipitation with a polyclonal
antiserum (Santa Cruz Biotechnologies, Santa Cruz, CA) that recognizes
the C-terminal sequences of both PKC-
and PKC-
(these PKCs,
except for one amino acid, have identical sequences in their C-terminal
26 amino acids). After overnight incubation at 0-4 °C, precipitates
were collected on protein AG-Agarose beads, washed, and incubated for 8 min at 30 °C in 50 µl of buffer containing 50 mM
Tris/HCL (pH 7.5), 5 mM MgCl2, 100 µM Na3V04, 100 µM
Na4P207, 1 mM NaF, 100 µM phenylmethylsulfonyl fluoride, 3-5 µCi
[
-32P]ATP (NEN Life Science Products), 50 µM ATP, 4 µg of phosphatidylserine, and 40 µM 159Ser-PKC-
(amino acids
153-164)-NH2 substrate (Quality Controlled Biochemicals).
After incubation, aliquots of the reaction mixtures were spotted on P81
filter paper, washed in 5% acetic acid, and counted for
32P.
PI 3-Kinase Activation--
Membrane PI 3-kinase activity was
measured in rat adipocytes as described (12). In brief, after treatment
of intact cells with or without 300 nM insulin or 1 µM okadaic acid, cells were sonicated, post-nuclear
defatted homogenates were centrifuged at 400,000 × g
for 45 min, and resultant membranes were assayed for PI 3-kinase
activity. After assay, lipids were extracted and resolved by thin layer
chromatography (12). 32P radioactivity in
PI-3-PO4 (which migrates just below PI-4-PO4 in
this system) was quantitated in a Bio-Rad PhosphorImager. PI 3-kinase
activity was also measured in phosphotyrosine immunoprecipitates (antiserum obtained from Santa Cruz Biotechnologies).
Cell Transfections--
As described (6, 8, 13), rat adipocytes
were transiently co-transfected with hemagglutinin antigen (HA)-tagged
GLUT4 with or without kinase-inactive (KI) forms of PKC-
and PKC-
(described in Refs. 6, 8, and 13) or the activation-resistant double
mutant (T308A,S473A) form of PKB. (The double mutant form of PKB was
made by site-directed mutagenesis of the wild-type construct (6) using
the MORPH mutagenesis kit according to the manufacturer's instructions
(5 Prime
3 Prime, Inc., Boulder, CO). Mutagenic oligonucleotides
5'-CCA CTA TGA AGG CAT TTT GCG GAA CGC CGG-3' and
5'-TTC CCC CAG TTC GCC TAC TCG GCC AGT GGC ACA-3'
created point mutations T308A and S473A as well as silent mutations
that created a new BglI site and disrupted an
XmnI site. Mutations were confirmed by direct sequencing.)
In brief, 0.8 ml of 50% cell suspension was electroporated in the
presence of 3 µg of pCIS2 containing cDNA insert encoding
HA-GLUT4, and 7 µg of pCDNA3 containing no insert
(i.e. vector only) or cDNA insert encoding KI-PKC-
or
KI-PKC-
, or 7 or 14 µg pCIS2 containing no insert (i.e.
vector only) or cDNA insert encoding T308A,S473A-PKB. After
overnight incubation to allow time for expression of cDNA inserts,
the cells were washed and equilibrated in glucose-free Krebs-Ringer
phosphate medium, and treated for 30 min with or without 10 nM insulin or 1 µM okadaic acid. After
incubation, 2 mM potassium cyanide was added to immobilize
GLUT4, and cells were washed, counted, and examined for surface content
of HA-GLUT4 using mouse monoclonal anti-HA primary antibody (Babco,
Berkeley, CA) and 125I-labeled rabbit anti-mouse IgG second
antibody (Amersham Pharmacia Biotech). Note that, in the absence of
cDNA insert, the amounts of DNA used in these transfections have no
effect on either basal or insulin-stimulated HA-GLUT4 translocation (8,
13); also, note that KI-PKC-
does not inhibit GTP
S-stimulated
HA-GLUT4 translocation, which is independent of atypical PKCs (13).
Also note that HA-GLUT4 expression (assessed by blotting the HA
epitope) was not influenced by the presence of cDNA inserts. Thus,
observed inhibitory effects of KI-PKC-
and KI-PKC-
on HA-GLUT4
translocation specifically reflected changes in signaling factors used
by insulin and okadaic acid, rather than the GLUT4 translocation
process itself.
 |
RESULTS |
Studies of 2-DOG Uptake--
In rat adipocytes, okadaic acid (1 µM) provoked increases in 2-DOG uptake that were
approximately 30-50% of those provoked by maximally effective 10 nM insulin; moreover, PI 3-kinase inhibitors, wortmannin
and LY294002, inhibited effects of okadaic acid, as well as insulin, on
2-DOG uptake (Fig. 1). Inhibitors of
atypical PKCs, viz. RO 31-8220 and the cell-permeable
myristoylated PKC-
pseudosubstrate, also inhibited effects of
okadaic acid and insulin on 2-DOG uptake (Fig. 1). Note that the doses
of RO 31-8220 that were required to inhibit 2-DOG uptake (as
stimulated by both okadaic acid and insulin) were similar to those
previously found to inhibit atypical PKCs (8), but considerably greater
than those required to inhibit conventional PKCs (14, 15).

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Fig. 1.
Effects of RO 31-8220, cell-permeable
myristoylated PKC- /
pseudosubstrate, wortmannin, and LY294002 on okadaic acid- and
insulin-stimulated 2-DOG uptake in rat adipocytes. Cells were
equilibrated for 15 min with indicated concentrations of RO 31-8220, wortmannin, and LY294002, and for 60 min with the cell-permeable
myristoylated PKC- / pseudosubstrate to allow time for uptake (see
Ref. 8). Okadaic acid (1 µM) or insulin (10 nM) was then added, and after 30 min, 2-DOG uptake over 1 min was measured. Values are mean ± S.E. of four
determinations.
|
|
As in rat adipocytes, okadaic acid provoked increases in 2-DOG uptake
in 3T3/L1 adipocytes that were approximately 30-40% of those provoked
by maximally effective 100 nM insulin; these effects of
okadaic acid and insulin were also inhibited by wortmannin, RO
31-8220, and the myristoylated PKC-
pseudosubstrate (Fig. 2).

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Fig. 2.
Effects of wortmannin, RO 31-8220 and
cell-permeable myristoylated
PKC- / pseudosubstrate
on okadaic and insulin-stimulated 2-DOG uptake in 3T3/L1
adipocytes. Experiments were conducted as in Fig. 1, except that
100 nM insulin was used and 2-DOG uptake was measured over
5 min. Values are mean ± S.E. of four determinations.
|
|
Studies of PKC-
/
Activation--
Okadaic acid provoked time-
and dose-dependent increases in the activity of
immunoprecipitable PKC-
/
in rat adipocytes. Increases in
immunoprecipitable PKC-
/
enzyme activity varied between 50 and
80% at 15 min of treatment with 1 µM okadaic acid, and
these increases were approximately 50% of those provoked by insulin
(Fig. 3). As with 2-DOG uptake, okadaic
acid-induced increases in immunoprecipitable PKC-
/
enzyme
activity were inhibited by wortmannin and LY294002 (Fig. 3).

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Fig. 3.
Activation of immunoprecipitable
PKC- / by okadaic acid
and insulin in rat adipocytes. A, cells were treated
for indicated times with 1 µM okadaic acid; B,
cells were treated for 15 min with indicated concentrations of okadaic
acid; C, cells were treated first with 100 nM
wortmannin or 100 µM LY294002 for 15 min, and then with 1 µM okadaic acid or 10 nM insulin for 15 min.
Combined PKC- / was immunoprecipitated and assayed in all cases
(A, B, C) after incubation. Values are
mean ± S.E. of four determinations in A and
B, and n determinations (shown in
parentheses) in C.
|
|
As in rat adipocytes, 1 µM okadaic acid provoked
wortmannin- and LY294002-inhibitable increases in PKC-
activity in
3T3/L1 adipocytes (these cells contain PKC-
, but not PKC-
, see
Ref. 16) that were approximately 50% of those provoked by insulin (Fig. 4).

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Fig. 4.
Activation of immunoprecipitable
PKC- by okadaic acid and insulin in 3T3/L1
adipocytes. Cells were treated with 100 nM wortmannin
or 100 µM LY294002 for 30 min before treatment with 1 µM okadaic acid or 100 nM insulin for 15 min.
After incubation, plates were scraped, cells were collected, and cell
lysates were subjected to immunoprecipitation and PKC- was assayed.
Values are mean ± S.E. of n determinations (shown in
parentheses).
|
|
Studies of PI 3-kinase Activation--
Okadaic acid provoked
increases in membrane-associated PI 3-kinase activity, which were
comparable to those observed with insulin treatment in rat adipocytes
(Fig. 5). In contrast, okadaic acid had
no effect on PI 3-kinase that was recovered in anti-phosphotyrosine immunoprecipitates, whereas insulin markedly increased
phosphotyrosine-associated PI 3-kinase activity (data not shown).

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Fig. 5.
Effects of okadaic acid and insulin on
membrane-associated PI 3-kinase activity in rat adipocytes. Cells
were treated with 300 nM insulin or 1 µM
okadaic acid for 15 min, following which, membrane fractions were
harvested and assayed for PI 3-kinase activity. A representative
autoradiogram showing changes in 32P-labeled
PI-3-PO4 is shown in the inset. Bars denote mean ± S.E. relative increases in 32P-labeled PI-3-PO4
(quantitated by PhosphorImager analysis) caused by okadaic acid and
insulin treatment in n determinations (shown in
parentheses).
|
|
Transfection Studies--
Okadaic acid provoked increases in the
translocation of HA-GLUT4 to the plasma membrane that were
approximately 40-60% of those induced by insulin in transiently
transfected rat adipocytes (Figs. 6 and
7). Co-transfection of KI-PKC-
inhibited the stimulatory effects of okadaic acid, as well as insulin,
on HA-GLUT4 translocation (Fig. 6) (see Ref. 13 for more detailed
studies of inhibitory effects of KI-PKC-
and KI-PKC-
in
insulin-stimulated adipocytes). Note that PKC-
and PKC-
apparently function interchangeably in supporting insulin-stimulated
HA-GLUT4 translocation (see Ref. 13).

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Fig. 6.
Effects of expression of
KI-PKC- and KI-PKC-
on HA-GLUT4 translocation during treatment of rat adipocytes with
okadaic acid and insulin. Cells were co-transfected with pCIS2
containing cDNA encoding HA-GLUT4 (all cells), and where indicated,
pCDNA3 containing cDNA insert encoding KI-PKC- or
KI-PKC- , or no insert (i.e. vector only). After overnight
incubation to allow time for expression (see expression data in Ref.
13), cells were washed, suspended in glucose-free Krebs-Ringer
phosphate medium, and treated for 30 min with 1 µM
okadaic acid or 10 nM insulin. Cell surface HA-GLUT4 was
then measured. See "Experimental Procedures" for other details.
Values are mean ± S.E. of n determinations (shown in
parentheses).
|
|

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Fig. 7.
Effects of expression of the
activation-resistant double mutant (T308A,S473A) form of PKB on okadaic
acid-stimulated HA-GLUT4 translocation in rat adipocytes. Cells
were transfected as in Fig. 6, except that, along with the
pCIS2/HA-GLUT4 cDNA construct, 7 or 14 µg pCIS2 containing no
insert (Vectors) or cDNA insert encoding T308A,S473A-PKB was used,
as indicated. Note that total amount of pCIS2 (± inserts) was kept
constant in all samples during electroporation at 17 µg of DNA, 0.8 ml of 50% adipocyte suspension by varying the amount of insert-free
vector. Values are mean ± S.E. of n determinations
(shown in parentheses). The inset depicts levels of PKB in
cells transfected without (0) and with 7 or 14 µg of pCIS2 with
cDNA insert encoding mutant PKB.
|
|
In contrast to KI-PKC-
, the double mutant T308A,S473A-PKB, which
acts as a dominant-negative for PKB-mediated processes (7), had no
appreciable effect on okadaic acid-stimulated increases in HA-GLUT4
translocation and caused only a mild inhibition (10-20%) of
insulin-stimulated HA-GLUT4 translocation (Fig. 7).
 |
DISCUSSION |
We found that in both rat adipocytes and 3T3/L1 adipocytes,
okadaic acid provoked increases in the activity of immunoprecipitable PKC-
/
; moreover, based upon studies with wortmannin and LY294002, the activation of PKC-
/
by okadaic acid appeared to be dependent upon PI 3-kinase. In keeping with this apparent dependence on PI
3-kinase, the activation of PKC-
/
by okadaic acid was associated with apparent increases in membrane-associated PI 3-kinase activity in
rat adipocytes. However, the mechanism whereby membrane-associated PI
3-kinase was activated by okadaic acid in rat adipocytes was unclear,
because okadaic acid did not provoke increases in the activity of PI
3-kinase that was recovered in phosphotyrosine immunoprecipitates.
Because the latter primarily reflects the activation of Src homology 2 domains in the p85 subunit of PI 3-kinase, the possibility remains that
okadaic acid may alter the activity of the p110 catalytic subunit of PI
3-kinase independently of the p85 subunit but nevertheless inhibitable
by wortmannin and LY294002.
Despite the evidence for PI 3-kinase activation during okadaic acid
action, alternative explanations for PKC-
/
activation should also
be considered. One such alternative is that okadaic acid may have
activated 3-phosphoinositide-dependent kinase-1 (PDK-1),
which, in conjunction with D3-PO4 polyphosphoinositides, serves to activate both PKB (16, 17) and PKC-
(18, 19); in this
case, basal PI 3-kinase activity may be required to support the
activity of PDK-1, and this could explain the inhibition of PKC-
/
activation by wortmannin and LY294002.
In keeping with the finding that okadaic acid-induced activation of
PKC-
/
appeared to dependent upon PI 3-kinase or PDK-1, PKB,
another protein kinase signaling factor that operates downstream of PI
3-kinase and PDK-1 (16, 17), has also been found to be activated by
okadaic acid in rat adipocytes (2). Thus, several independent lines of
evidence lend support to the postulation that okadaic acid activates or
requires continued activity of PI 3-kinase and/or PDK-1. Obviously,
activation of PI 3-kinase or PDK-1 may explain why effects of okadaic
acid on glucose transport are inhibited by wortmannin and LY294002 in
both rat adipocytes and 3T3/L1 adipocytes.
Whereas okadaic acid appeared to activate PI 3-kinase and PI
3-kinase-dependent processes, viz. PKB,
PKC-
/
, GLUT4 translocation, and glucose transport in rat and
3T3/L1 adipocytes, the situation in rat skeletal muscle (4) and human
adipocytes (3) may be decidedly different. Indeed, the effects of
okadaic acid on glucose transport in these tissues are
wortmannin-insensitive, and therefore appear to be independent of PI
3-kinase. Further studies are needed to see if okadaic acid activates
PKC-
/
in human adipocytes and rat skeletal muscles.
Although okadaic acid activates PKB in rat adipocytes (2), and
constitutively active PKB stimulates GLUT4 translocation (6) in rat
adipocytes (1, 6) and 3T3/L1 (20) adipocytes, the present findings in
transfection studies suggested that PKB was not required for okadaic
acid-stimulated GLUT4 translocation in rat adipocytes. These findings
are similar to those observed during insulin action in 3T3/L1
adipocytes (7), in which it was concluded that PKB is not required for
insulin-induced activation of glucose transport. On the other hand, in
rat adipocytes, a small fraction (approximately 20%) of insulin
effects on HA-GLUT4 translocation is blocked by KI-PKB (6), as well as
by an activation-resistant T308A,S473A-PKB double
mutant,2 suggesting a partial
requirement for PKB. Further studies are needed to see if there are
different requirements for insulin- and okadaic acid-induced effects on
GLUT4 translocation in different cell types.
In summary, okadaic acid activated PKC-
/
in both rat adipocytes
and 3T3/L1 adipocytes by a mechanism that appeared to be dependent upon
PI 3-kinase or PDK-1. Moreover, the activation of PKC-
/
was
required for effects of okadaic acid on GLUT4 translocation and glucose transport.
 |
ACKNOWLEDGEMENT |
We thank Sara M. Busquets for her invaluable
secretarial assistance.
 |
FOOTNOTES |
*
This work was supported by funds from the Department of
Veterans Affairs Merit Review Program, National Institutes of Health Research Grant 2R01DK38079-09A1, and the Hypertension-Endocrine Branch,
NHLBI, National Institutes of Health.The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
§
To whom correspondence should be addressed: Research Service (VAR
151), J. A. Haley VA Hospital, 13000 Bruce B. Downs Blvd., Tampa,
FL 33612. Tel.: 813-972-7662; Fax: 813-972-7623; E-mail: rfarese{at}com1.med.usf.edu.
2
M. L. Standaert, G. Bandyopadhyay, M. P. Sajan, L. Cong, M. J. Quon, and R. V. Farese, unpublished observations.
 |
ABBREVIATIONS |
The abbreviations used are:
PI, phosphatidylinositol;
PKB, protein kinase B;
IRS-1, insulin receptor
substrate-1;
KI, kinase inactive;
2-DOG, 2-[3H]deoxyglucose;
PKC, protein kinase C;
HA, hemagglutinin antigen;
GTP
S, guanosine
5'-3-O-(thio)triphosphate;
PDK-1, 3-phosphoinositidedependent kinase-1.
 |
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