Correspondence to Melitta Schachner: melitta.schachner{at}zmnh.uni-hamburg.de
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Abbreviations used in this paper: FGFR, FGF receptor; NCAM, neural cell adhesion molecule.
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The activity of Src family tyrosine kinases is regulated by phosphorylation (Brown and Cooper, 1996; Thomas and Brugge, 1997; Bhandari et al., 1998; Hubbard, 1999; Petrone and Sap, 2000). The two best-characterized tyrosine phosphorylation sites in Src family tyrosine kinases perform opposing regulatory functions. The site within the enzyme's activation loop (Tyr-420 in p59fyn) undergoes autophosphorylation, which is crucial for achieving full kinase activity. In contrast, phosphorylation of the COOH-terminal site (Tyr-531 in p59fyn) inhibits kinase activity through intramolecular interaction between phosphorylated Tyr-531 and the SH2 domain in p59fyn, which stabilizes a noncatalytic conformation.
A well known activator of Src family tyrosine kinases is the receptor protein tyrosine phosphatase RPTP (Zheng et al., 1992, 2000; den Hertog et al., 1993; Su et al., 1996; Ponniah et al., 1999). It contains two cytoplasmic catalytic domains, D1 and D2, of which only D1 is significantly active in vitro and in vivo (Wang and Pallen, 1991; den Hertog et al., 1993; Wu et al., 1997; Harder et al., 1998). To activate Src family tyrosine kinase, constitutively phosphorylated pTyr789 at the COOH-terminal of RPTP
binds the SH2 domain of Src family tyrosine kinase that disrupts the intra-molecular association between the SH2 and SH1 domains of the kinase. This initial binding is followed by binding between the inhibitory COOH-terminal phosphorylation site of the Src family tyrosine kinase (pTyr531 in p59fyn) and the D1 domain of RPTP
resulting in dephosphorylation of the inhibitory COOH-terminal phosphorylation sites in Src family tyrosine kinases (Zheng et al., 2000). These sites are hyperphosphorylated in cells lacking RPTP
, and kinase activity of pp60c-src and p59fyn in RPTP
-deficient mice is reduced (Ponniah et al., 1999). Like p59fyn and NCAM, RPTP
is particularly abundant in the brain (Kaplan et al., 1990; Krueger et al., 1990), accumulates in growth cones (Helmke et al., 1998), and is involved in neural cell migration and neurite outgrowth (Su et al., 1996; Yang et al., 2002; Petrone et al., 2003).
Remarkably, a close homologue of RPTP, CD45, associates with the membrane-cytoskeleton linker protein spectrin (Lokeshwar and Bourguignon, 1992; Iida et al., 1994), a binding partner of NCAM (Leshchyns'ka et al., 2003). Following this lead, we investigated the possibility that RPTP
is involved in NCAM-induced p59fyn activation. We show that the intracellular domains of NCAM140 and RPTP
interact directly and that this interaction is enhanced by spectrin-mediated Ca2+-dependent cross-linking of NCAM and RPTP
. Levels of p59fyn associated with NCAM correlate with the ability of NCAM-associated RPTP
to bind to p59fyn, and the NCAMp59fyn complex is disrupted in RPTP
-deficient brains implicating RPTP
as linker molecule between NCAM and p59fyn. RPTP
redistributes to lipid rafts in response to NCAM activation and RPTP
levels are reduced in lipid rafts from NCAM-deficient mice, suggesting that NCAM recruits RPTP
to lipid rafts to activate p59fyn. Finally, NCAM-mediated p59fyn activation is abolished in RPTP
-deficient neurons and NCAM-induced neurite outgrowth is blocked in RPTP
-deficient neurons or neurons transfected with dominant-negative RPTP
mutants, demonstrating that RPTP
is a major phosphatase involved in NCAM-mediated signaling.
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
|
NCAM140 is the most potent RPTP-binding NCAM isoform
To identify the NCAM isoform interacting with RPTP, we expressed NCAM120, NCAM140, and NCAM180 in CHO cells and analyzed their association with RPTP
by coimmunoprecipitation. CHO cells endogenously express RPTP
that was detected with RPTP
antibodies as a band with a molecular mass identical to RPTP
detected in brain homogenates (unpublished data). Although transfected CHO cells expressed NCAM120, NCAM140, and NCAM180 in similar amounts, RPTP
coimmunoprecipitated only with NCAM140 (Fig. 3 A). However, after prolonged exposure of the film we could also detect RPTP
in NCAM180 immunoprecipitates (unpublished data). RPTP
did not coimmunoprecipitate with NCAM120. We conclude that RPTP
associates predominantly with NCAM140 and to a lesser extent with NCAM180.
|
RPTP binds NCAM140 via the D2 domain and links NCAM140 to p59fyn
To identify the part of the intracellular domain of RPTP responsible for the interaction with NCAM140, we coexpressed, in CHO cells, NCAM140 together with the wild-type form of RPTP
(wtRPTP
), RPTP
lacking the D2 domain (RPTP
D2), or catalytically inactive form of RPTP
containing a mutation within the D1 catalytic domain (RPTP
C433S) and analyzed binding of NCAM140 to these RPTP
mutants by coimmunoprecipitation. All transfected RPTP
constructs contained the HA tag to distinguish them from endogenous RPTP
. As seen for endogenous RPTP
, transfected wtRPTP
coimmunoprecipitated with NCAM140 (Fig. 4 A). Similar amounts of RPTP
C433S coimmunoprecipitated with NCAM140, whereas RPTP
D2 did not coimmunoprecipitate (Fig. 4 A), indicating that the D2 domain is required for the interaction between RPTP
and NCAM140.
|
To analyze the role of RPTP in NCAM140p59fyn complex formation, we coimmunoprecipitated p59fyn with NCAM140 in the presence of RPTP
mutants. In CHO cells cotransfected with NCAM140 and wtRPTP
, p59fyn coimmunoprecipitated with NCAM140 (Fig. 4 A). The amount of p59fyn coimmunoprecipitated with NCAM140 was reduced in cells cotransfected with RPTP
C433S (Fig. 4 A), correlating with the reduced ability of this catalytically inactive RPTP
mutant to bind p59fyn (see previous paragraph; Zheng et al., 2000). When NCAM140 was cotransfected with RPTP
D2, p59fyn no longer coimmunoprecipitated with NCAM140 (Fig. 4 A). Because RPTP
D2 binds p59fyn (Fig. 4 A), it is conceivable that this mutant, which does not bind NCAM140, competes with endogenous RPTP
for binding to p59fyn and thus inhibits NCAM140p59fyn complex formation.
To extend this analysis to neurons, we transfected hippocampal neurons with GFP alone or cotransfected with GFP and RPTPD2 or RPTP
C433S and analyzed the redistribution of p59fyn to NCAM clusters after cross-linking NCAM with NCAM antibodies (Fig. 4 B). In neurons transfected with RPTP
D2 or RPTP
C433S, the level of p59fyn in NCAM clusters was reduced by
30% when compared with GFP only transfected cells, suggesting that RPTP
D2 or RPTP
C433S inhibit NCAMp59fyn complex formation by competing with endogenous RPTP
. The combined observations indicate that NCAM140p59fyn complex formation correlates with the ability of NCAM140-associated RPTP
to bind to p59fyn, implicating RPTP
as a linker between NCAM140 and p59fyn.
Association between NCAM and p59fyn and NCAM-mediated p59fyn activation are abolished in RPTP-deficient neurons
To substantiate further our finding that RPTP is a linker protein between NCAM and p59fyn, we analyzed p59fyn activation and association of p59fyn with NCAM in RPTP
-deficient brains. As for NCAM-deficient brains, levels of p59fyn dephosphorylated at Tyr-531 and levels of p59fyn phosphorylated at Tyr-420 were reduced in brain homogenates of RPTP
-deficient mice (Fig. 5 A), further suggesting that RPTP
plays a role in NCAM-mediated p59fyn activation in the brain. To analyze the role of RPTP
in the formation of the complex between NCAM and p59fyn, we immunoprecipitated NCAM from wild-type and RPTP
-deficient brains and probed immunoprecipitates with antibodies against p59fyn. Whereas p59fyn coimmunoprecipitated with NCAM from wild-type brains, p59fyn did not coimmunoprecipitate with NCAM from RPTP
-deficient brains (Fig. 5 B). Furthermore, when NCAM was clustered at the surface of wild-type and RPTP
-deficient cultured hippocampal neurons, levels of p59fyn were significantly reduced in NCAM clusters in RPTP
-deficient neurons when compared with wild-type cells (Fig. 5 C), indicating that RPTP
is required for complex formation between NCAM and p59fyn.
|
Formation of the complex between RPTP and NCAM is enhanced by Ca2+
Coimmunoprecipitation experiments were performed either in the presence of Ca2+ or with 2 mM EDTA, a Ca2+-sequestering agent. Whereas RPTP coimmunoprecipitated with NCAM from brain homogenates under both conditions, coimmunoprecipitated complexes were reduced by
60% in the presence of EDTA (Fig. 6 A), suggesting that Ca2+ promotes formation of the NCAMRPTP
complex. These results are in accordance with findings of Zeng et al. (1999), who found that NCAM and RPTP
did not coimmunoprecipitate in the presence of EDTA. To analyze if the direct interaction between NCAM and RPTP
is Ca2+ dependent, we assayed binding of the intracellular domain of NCAM140 to the intracellular domain of RPTP
by ELISA in the presence or absence of Ca2+ (Fig. 6 B), showing that the direct interaction is Ca2+ independent and suggesting that additional binding partners of NCAM and/or RPTP
may enhance complex formation in a Ca2+-dependent manner. Spectrin, which directly interacts with the intracellular domain of NCAM (Leshchyns'ka et al., 2003) and contains a Ca2+ binding domain (De Matteis and Morrow, 2000), is one of the possible candidates. Indeed, RPTP
coimmunoprecipitated with spectrin from brain homogenates (Fig. 6 C). In the presence of 2 mM EDTA, RPTP
coimmunoprecipitating with spectrin was reduced by
80% (Fig. 6 C), whereas coimmunoprecipitation of NCAM with spectrin did not depend on Ca2+ (Fig. 6 C). We conclude that RPTP
directly interacts with NCAM in a Ca2+-independent manner. However, formation of the complex is enhanced by Ca2+-dependent cross-linking of NCAM140 and RPTP
via spectrin.
|
|
NCAM-induced neurite outgrowth depends on NCAM association with RPTP
NCAM-induced neurite outgrowth depends on p59fyn activation (Kolkova et al., 2000), suggesting that NCAM association with RPTP may be involved. To analyze the role of protein tyrosine phosphatases in NCAM-induced neurite outgrowth, we incubated cultured hippocampal neurons with 100 µM vanadate, an inhibitor of these phosphatases (Helmke et al., 1998). NCAM-Fcenhanced neurite outgrowth was abolished by vanadate, indicating that activation of protein tyrosine phosphatases is required for NCAM-mediated neurite outgrowth. Vanadate did not affect neurite outgrowth in nonstimulated neurons, indicating that vanadate does not lead to nonspecific impairments (Fig. 8 A). To directly assess the role of RPTP
in NCAM-induced neurite outgrowth, we transfected hippocampal neurons with the dominant-negative mutants of RPTP
. Both, RPTP
D2, which does not bind NCAM but associates with p59fyn, and catalytically inactive RPTP
C433S, which associates with NCAM but binds p59fyn with a lower efficiency than endogenous RPTP
, inhibited association of NCAM with p59fyn by competing with endogenous RPTP
(Fig. 4). In neurons transfected with GFP only, stimulation with NCAM-Fc significantly enhanced neurite length when compared with control nonstimulated neurons (Fig. 8 B). However, neurons transfected with RPTP
D2 or RPTP
C433S remained unresponsive to NCAM-Fc stimulation (Fig. 8 B), indicating that RPTP
plays a major role in NCAM-induced neurite outgrowth. To confirm this finding, we analyzed NCAM-mediated neurite outgrowth in hippocampal neurons from RPTP
-deficient mice. Whereas NCAM-Fc enhanced neurite outgrowth in neurons from RPTP
wild-type littermates by
100%, NCAM-Fcinduced neurite outgrowth was completely abolished in RPTP
-deficient neurons (Fig. 8 C), further confirming that RPTP
is required for NCAM-mediated neurite outgrowth.
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Role of Ca2+ in NCAMRPTPp59fyn complex formation
Interactions between NCAM and RPTP and NCAMRPTP
p59fyn complex formation leading to neurite outgrowth are tightly regulated (Fig. 9). First, whereas direct interaction between NCAM and RPTP
is Ca2+ independent, NCAMRPTP
complex formation is enhanced by Ca2+-dependent cross-linking via spectrin. Remarkably, NCAM activation results in an increase in intracellular Ca2+ concentration via influx through Ca2+ channels or release from intracellular stores, and may thus provide a positive feedback loop between NCAM activation and NCAMRPTP
complex formation involving spectrin. RPTP
binding to spectrin may also elevate RPTP
enzymatic dephosphorylation activity (Lokeshwar and Bourguignon, 1992). Interestingly, NCAM activation also induces activation of PKC (Kolkova et al., 2000; Leshchyns'ka et al., 2003), which is known to phosphorylate RPTP
and stimulate its activity (den Hertog et al., 1995; Tracy et al., 1995; Zheng et al., 2002). Thus, a network of activated intracellular signaling molecules may underlie the induction and maintenance of NCAM-mediated neurite outgrowth. It is interesting in this respect that the NCAM140 isoform predominates in these interactions: it interacts more efficiently with p59fyn via RPTP
and enhances neurite outgrowth more vigorously than NCAM180 (Niethammer et al., 2002). The structural dispositions of NCAM140 for this preference will remain to be established.
|
Potential role of protein tyrosine phosphatases in signaling mediated by other cell adhesion molecules
Besides NCAM, activation of L1 and CHL1, other cell adhesion molecules of the immunoglobulin superfamily, also results in the activation of Src family tyrosine kinases (Schmid et al., 2000; Buhusi et al., 2003). As for NCAM, the intracellular domains of L1 and CHL1 do not possess structural motif for protein tyrosine phosphatase activity, suggesting that yet unidentified protein tyrosine phosphatases may be involved. Identification of protein tyrosine phosphatases associated with other cell adhesion molecules of the immunoglobulin superfamily and conjunctions with RPTP-activated integrins (Zeng et al., 2003) will be an important next step in the elucidation of the mechanisms that cell adhesion molecules use differentially to guide cell migration and neurite outgrowth in the developing nervous system.
![]() |
Materials and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Animals
To compare wild-type and NCAM-deficient mice, C57BL/6J mice and NCAM-deficient mice (Cremer et al., 1994) inbred for at least nine generations onto the C57BL/6J background were used. NCAM-deficient mice were a gift of H. Cremer (Developmental Biology Institute of Marseille, Marseille, France).To compare wild-type and RPTP-deficient mice, RPTP
-positive and -negative littermates obtained from heterozygous breeding were used (see online supplemental material).
Image acquisition and manipulation
Coverslips were embedded in Aqua-Poly/Mount (Polysciences, Inc.). Images were acquired at RT using a confocal laser scanning microscope (model LSM510; Carl Zeiss MicroImaging, Inc.), LSM510 software (version 3; Carl Zeiss MicroImaging, Inc.), and oil Plan-Neofluar 40x objective (NA 1.3; Carl Zeiss MicroImaging, Inc.) at 3x digital zoom. Contrast and brightness of the images were further adjusted in Photo-Paint 9 (Corel Corporation).
Detergent extraction of cultured neurons
Cells washed in PBS were incubated for 1 min in cold microtubule-stabilizing buffer (2 mM MgCl2, 10 mM EGTA, and 60 mM Pipes, pH 7.0) and extracted 8 min on ice with 1% Triton X-100 in microtubule-stabilizing buffer as described previously (Ledesma et al., 1998). After washing with PBS, cells were fixed with cold 4% formaldehyde in PBS.
Colocalization analysis
Colocalization quantification was performed as described previously (Leshchyns'ka et al., 2003). In brief, an NCAM cluster was defined as an accumulation of NCAM labeling with a mean intensity at least 30% higher than background. NCAM clusters were automatically outlined using the threshold function of the Scion Image software (Scion Corporation). Within the outlined areas the mean intensities of NCAM, RPTP, p59fyn, or GM1 labeling associated with NCAM cluster were measured. The same threshold was used for all groups. All experiments were performed two to three times with the same effect. Colocalization profiles were plotted using ImageJ software (National Institutes of Health).
DNA constructs
Rat NCAM140 and NCAM180/pcDNA3 were a gift of P. Maness (University of North Carolina, Chapel Hill, NC). Rat NCAM120 (a gift of E. Bock, University of Copenhagen, Copenhagen, Denmark) was subcloned into the pcDNA3 vector (Invitrogen) by two EcoRI sites. The EGFP plasmid was purchased from CLONTECH Laboratories, Inc. cDNAs encoding intracellular domains of NCAM140 and NCAM180 were as described previously (Sytnyk et al., 2002; Leshchyns'ka et al., 2003). The plasmid encoding the intracellular domain of RPTP was a gift of C.J. Pallen. Wild-type RPTP
, RPTP
C433S, and RPTP
D2 (containing RPTP
residues 1516 [last 6 residues: KIYNKI]) were as described previously (den Hertog and Hunter, 1996; Blanchetot and den Hertog, 2000; Buist et al., 2000).
Online supplemental material
Details on cultures and transfection of hippocampal neurons and CHO cells, immunofluorescence labeling, ELISA and pull-down assay, coimmunoprecipitation, isolation of lipid enriched microdomains, gel electrophoresis, immunoblotting, and generation of RPTP-deficient mice are given in online supplemental material. Online supplemental material is available at http://www.jcb.org/cgi/content/full/jcb.200405073/DC1.
![]() |
Acknowledgments |
---|
This work was supported by Zonta Club, Hamburg-Alster (I. Leshchyns'ka), and Deutsche Forschungsgemeinschaft (I. Leshchyns'ka, V. Sytnyk, and M. Schachner).
Submitted: 12 May 2004
Accepted: 11 November 2004
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Beggs, H.E., P. Soriano, and P.F. Maness. 1994. NCAM-dependent neurite outgrowth is inhibited in neurons from Fyn-minus mice. J. Cell Biol. 127:825833.[Abstract]
Beggs, H.E., S.C. Baragona, J.J. Hemperly, and P.F. Maness. 1997. NCAM140 interacts with the focal adhesion kinase p125(fak) and the SRC-related tyrosine kinase p59(fyn). J. Biol. Chem. 272:83108319.
Bhandari, V., K.L. Lim, and C.J. Pallen. 1998. Physical and functional interactions between receptor-like protein-tyrosine phosphatase alpha and p59fyn. J. Biol. Chem. 273:86918698.
Blanchetot, C., and J. den Hertog. 2000. Multiple interactions between receptor protein-tyrosine phosphatase (RPTP) alpha and membrane-distal protein-tyrosine phosphatase domains of various RPTPs. J. Biol. Chem. 275:1244612452.
Brown, M.T., and J.A. Cooper. 1996. Regulation, substrates and functions of src. Biochim. Biophys. Acta. 1287:121149.[CrossRef][Medline]
Buhusi, M., B.R. Midkiff, A.M. Gates, M. Richter, M. Schachner, and P.F. Maness. 2003. Close homolog of L1 is an enhancer of integrin-mediated cell migration. J. Biol. Chem. 278:2502425031.
Buist, A., C. Blanchetot, L.G. Tertoolen, and J. den Hertog. 2000. Identification of p130cas as an in vivo substrate of receptor protein-tyrosine phosphatase alpha. J. Biol. Chem. 275:2075420761.
Cavallaro, U., J. Niedermeyer, M. Fuxa, and G. Christofori. 2001. N-CAM modulates tumour-cell adhesion to matrix by inducing FGF-receptor signalling. Nat. Cell Biol. 3:650657.[CrossRef][Medline]
Cremer, H., R. Lange, A. Christoph, M. Plomann, G. Vopper, J. Roes, R. Brown, S. Baldwin, P. Kraemer, S. Scheff, et al. 1994. Inactivation of the N-CAM gene in mice results in size reduction of the olfactory bulb and deficits in spatial learning. Nature. 367:455459.[CrossRef][Medline]
Crossin, K.L., and L.A. Krushel. 2000. Cellular signaling by neural cell adhesion molecules of the immunoglobulin superfamily. Dev. Dyn. 218:260279.[CrossRef][Medline]
De Matteis, M.A., and J.S. Morrow. 2000. Spectrin tethers and mesh in the biosynthetic pathway. J. Cell Sci. 113:23312343.
den Hertog, J., and T. Hunter. 1996. Tight association of GRB2 with receptor protein-tyrosine phosphatase alpha is mediated by the SH2 and C-terminal SH3 domains. EMBO J. 15:30163027.[Abstract]
den Hertog, J., C.E. Pals, M.P. Peppelenbosch, L.G. Tertoolen, S.W. de Laat, and W. Kruijer. 1993. Receptor protein tyrosine phosphatase alpha activates pp60c-src and is involved in neuronal differentiation. EMBO J. 12:37893798.[Abstract]
den Hertog, J., S. Tracy, and T. Hunter. 1994. Phosphorylation of receptor protein-tyrosine phosphatase alpha on Tyr789, a binding site for the SH3-SH2-SH3 adaptor protein GRB-2 in vivo. EMBO J. 13:30203032.[Abstract]
den Hertog, J., J. Sap, C.E. Pals, J. Schlessinger, and W. Kruijer. 1995. Stimulation of receptor protein-tyrosine phosphatase alpha activity and phosphorylation by phorbol ester. Cell Growth Differ. 6:303307.[Abstract]
Filipp, D., J. Zhang, B.L. Leung, A. Shaw, S.D. Levin, A. Veillette, and M. Julius. 2003. Regulation of Fyn through translocation of activated Lck into lipid rafts. J. Exp. Med. 197:12211227.
Gennarini, G., M. Hirn, H. Deagostini-Bazin, and C. Goridis. 1984. Studies on the transmembrane disposition of the neural cell adhesion molecule N-CAM. The use of liposome-inserted radioiodinated N-CAM to study its transbilayer orientation. Eur. J. Biochem. 142:6573.[Abstract]
Harder, K.W., N.P. Moller, J.W. Peacock, and F.R. Jirik. 1998. Protein-tyrosine phosphatase alpha regulates Src family kinases and alters cell-substratum adhesion. J. Biol. Chem. 273:3189031900.
He, Q., and K.F. Meiri. 2002. Isolation and characterization of detergent-resistant microdomains responsive to NCAM-mediated signaling from growth cones. Mol. Cell. Neurosci. 19:1831.[CrossRef][Medline]
Helmke, S., K. Lohse, K. Mikule, M.R. Wood, and K.H. Pfenninger. 1998. SRC binding to the cytoskeleton, triggered by growth cone attachment to laminin, is protein tyrosine phosphatase-dependent. J. Cell Sci. 111:24652475.
Hubbard, S.R. 1999. Src autoinhibition: let us count the ways. Nat. Struct. Biol. 6:711714.[CrossRef][Medline]
Iida, N., V.B. Lokeshwar, and L.Y. Bourguignon. 1994. Mapping the fodrin binding domain in CD45, a leukocyte membrane-associated tyrosine phosphatase. J. Biol. Chem. 269:2857628583.
Juliano, R.L. 2002. Signal transduction by cell adhesion receptors and the cytoskeleton: functions of integrins, cadherins, selectins, and immunoglobulin-superfamily members. Annu. Rev. Pharmacol. Toxicol. 42:283323.[CrossRef][Medline]
Kamiguchi, H., and V. Lemmon. 2000. IgCAMs: bidirectional signals underlying neurite growth. Curr. Opin. Cell Biol. 12:598605.[CrossRef][Medline]
Kaplan, R., B. Morse, K. Huebner, C. Croce, R. Howk, M. Ravera, G. Ricca, M. Jaye, and J. Schlessinger. 1990. Cloning of three human tyrosine phosphatases reveals a multigene family of receptor-linked protein-tyrosine-phosphatases expressed in brain. Proc. Natl. Acad. Sci. USA. 87:70007004.[Abstract]
Kolkova, K., V. Novitskaya, N. Pedersen, V. Berezin, and E. Bock. 2000. Neural cell adhesion molecule-stimulated neurite outgrowth depends on activation of protein kinase C and the Ras-mitogen-activated protein kinase pathway. J. Neurosci. 20:22382246.
Kramer, E.M., C. Klein, T. Koch, M. Boytinck, and J. Trotter. 1999. Compartmentation of Fyn kinase with glycosylphosphatidylinositol-anchored molecules in oligodendrocytes facilitates kinase activation during myelination. J. Biol. Chem. 274:2904229049.
Krueger, N.X., M. Streuli, and H. Saito. 1990. Structural diversity and evolution of human receptor-like protein tyrosine phosphatases. EMBO J. 9:32413252.[Abstract]
Ledesma, M.D., K. Simons, and C.G. Dotti. 1998. Neuronal polarity: essential role of protein-lipid complexes in axonal sorting. Proc. Natl. Acad. Sci. USA. 95:39663971.
Leshchyns'ka, I., V. Sytnyk, J.S. Morrow, and M. Schachner. 2003. Neural cell adhesion molecule (NCAM) association with PKCß2 via ßI spectrin is implicated in NCAM-mediated neurite outgrowth. J. Cell Biol. 161:625639.
Lokeshwar, V.B., and L.Y. Bourguignon. 1992. Tyrosine phosphatase activity of lymphoma CD45 (GP180) is regulated by a direct interaction with the cytoskeleton. J. Biol. Chem. 267:2155121557.
Niethammer, P., M. Delling, V. Sytnyk, A. Dityatev, K. Fukami, and M. Schachner. 2002. Cosignaling of NCAM via lipid rafts and the FGF receptor is required for neuritogenesis. J. Cell Biol. 157:521532.
Paratcha, G., F. Ledda, and C.F. Ibanez. 2003. The neural cell adhesion molecule NCAM is an alternative signaling receptor for GDNF family ligands. Cell. 113:867879.[Medline]
Petrone, A., and J. Sap. 2000. Emerging issues in receptor protein tyrosine phosphatase function: lifting fog or simply shifting? J. Cell Sci. 113:23452354.
Petrone, A., F. Battaglia, C. Wang, A. Dusa, J. Su, D. Zagzag, R. Bianchi, P. Casaccia-Bonnefil, O. Arancio, and J. Sap. 2003. Receptor protein tyrosine phosphatase alpha is essential for hippocampal neuronal migration and long-term potentiation. EMBO J. 22:41214131.
Ponniah, S., D.Z. Wang, K.L. Lim, and C.J. Pallen. 1999. Targeted disruption of the tyrosine phosphatase PTPalpha leads to constitutive downregulation of the kinases Src and Fyn. Curr. Biol. 9:535538.[CrossRef][Medline]
Schmid, R.S., R.D. Graff, M.D. Schaller, S. Chen, M. Schachner, J.J. Hemperly, and P.F. Maness. 1999. NCAM stimulates the Ras-MAPK pathway and CREB phosphorylation in neuronal cells. J. Neurobiol. 38:542558.[CrossRef][Medline]
Schmid, R.S., W.M. Pruitt, and P.F. Maness. 2000. A MAP kinase-signaling pathway mediates neurite outgrowth on L1 and requires Src-dependent endocytosis. J. Neurosci. 20:41774188.
Su, J., L.T. Yang, and J. Sap. 1996. Association between receptor protein-tyrosine phosphatase RPTPalpha and the Grb2 adaptor. Dual Src homology (SH) 2/SH3 domain requirement and functional consequences. J. Biol. Chem. 271:2808628096.
Sytnyk, V., I. Leshchyns'ka, M. Delling, G. Dityateva, A. Dityatev, and M. Schachner. 2002. Neural cell adhesion molecule promotes accumulation of TGN organelles at sites of neuron-to-neuron contacts. J. Cell Biol. 159:649661.
Thomas, S.M., and J.S. Brugge. 1997. Cellular functions regulated by Src family kinases. Annu. Rev. Cell Dev. Biol. 13:513609.[CrossRef][Medline]
Tracy, S., P. van der Geer, and T. Hunter. 1995. The receptor-like protein-tyrosine phosphatase, RPTP alpha, is phosphorylated by protein kinase C on two serines close to the inner face of the plasma membrane. J. Biol. Chem. 270:1058710594.
van't Hof, W., and M.D. Resh. 1997. Rapid plasma membrane anchoring of newly synthesized p59fyn: selective requirement for NH2-terminal myristoylation and palmitoylation at cysteine-3. J. Cell Biol. 136:10231035.
von Wichert, G., G. Jiang, A. Kostic, K. De Vos, J. Sap, and M.P. Sheetz. 2003. RPTP- acts as a transducer of mechanical force on
v/ß3-integrincytoskeleton linkages. J. Cell Biol. 161:143153.
Walsh, F.S., and P. Doherty. 1997. Neural cell adhesion molecules of the immunoglobulin superfamily: role in axon growth and guidance. Annu. Rev. Cell Dev. Biol. 13:425456.[CrossRef][Medline]
Wang, Y., and C.J. Pallen. 1991. The receptor-like protein tyrosine phosphatase HPTP alpha has two active catalytic domains with distinct substrate specificities. EMBO J. 10:32313237.[Abstract]
Williams, E.J., P. Doherty, G. Turner, R.A. Reid, J.J. Hemperly, and F.S. Walsh. 1992. Calcium influx into neurons can solely account for cell contactdependent neurite outgrowth stimulated by transfected L1. J. Cell Biol. 119:883892.[Abstract]
Wu, L., A. Buist, J. den Hertog, and Z.Y. Zhang. 1997. Comparative kinetic analysis and substrate specificity of the tandem catalytic domains of the receptor-like protein-tyrosine phosphatase alpha. J. Biol. Chem. 272:69947002.
Yang, L.T., K. Alexandropoulos, and J. Sap. 2002. c-SRC mediates neurite outgrowth through recruitment of Crk to the scaffolding protein Sin/Efs without altering the kinetics of ERK activation. J. Biol. Chem. 277:1740617414.
Zeng, L., L. D'Alessandri, M.B. Kalousek, L. Vaughan, and C.J. Pallen. 1999. Protein tyrosine phosphatase (PTP
) and contactin form a novel neuronal receptor complex linked to the intracellular tyrosine kinase fyn. J. Cell Biol. 147:707714.
Zeng, L., X. Si, W.P. Yu, H.T. Le, K.P. Ng, R.M. Teng, K. Ryan, D.Z. Wang, S. Ponniah, and C.J. Pallen. 2003. PTP regulates integrin-stimulated FAK autophosphorylation and cytoskeletal rearrangement in cell spreading and migration. J. Cell Biol. 160:137146.[CrossRef][Medline]
Zheng, X.M., Y. Wang, and C.J. Pallen. 1992. Cell transformation and activation of pp60c-src by overexpression of a protein tyrosine phosphatase. Nature. 359:336339.[CrossRef][Medline]
Zheng, X.M., R.J. Resnick, and D. Shalloway. 2000. A phosphotyrosine displacement mechanism for activation of Src by PTPalpha. EMBO J. 19:964978.
Zheng, X.M., R.J. Resnick, and D. Shalloway. 2002. Mitotic activation of protein-tyrosine phosphatase alpha and regulation of its Src-mediated transforming activity by its sites of protein kinase C phosphorylation. J. Biol. Chem. 277:2192221929.