| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | ADVANCED SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Division of Oncology, Department of Cancer Biology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
2 Medical Proteomics Laboratory, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
 |
Abstract |
|---|
 Top Abstract IntroductionResultsDiscussionExperimental proceduresReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionResultsDiscussionExperimental proceduresReferences |
|---|
Fyn, a member of the Src-family of non-receptor tyrosine kinases (SFKs), is expressed at high levels in brain and is activated during the initial stages of myelination (Umemori et al. 1992, 1994). Fyn-knockout mice display severe hypomyelination, characterized by a decrease in total myelin content and a reduced number of myelin lamellae on axons (Umemori et al. 1999; Goto et al. 2004). Fyn is essential for the morphological differentiation and survival of oligodendrocytes (Osterhout et al. 1999; Colognato et al. 2004). Fyn kinase activity increases upon differentiation of primary oligodendrocytes (Osterhout et al. 1999). Hence, Fyn functions as a critical mediator in the oligodendroglial signaling pathway to control CNS myelinogensis. Recent studies have identified several transmembrane proteins that activate Fyn in oligodendrocytes, including FcR
, CD45 and integrin 
6ß1 (Nakahara et al. 2003, 2005; Colognato et al. 2004; Liang et al. 2004). However, Fyn substrates in oligodendrocytes have not been studied in detail, although p190RhoGAP, p250GAP and QKI have been implicated as downstream targets of Fyn in these cells (Wolf et al. 2001; Taniguchi et al. 2003; Lu et al. 2005).
Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase that is a known substrate of SFKs. Integrins and other extracellular signals activate FAK, which in turn leads to multiple cellular processes including cell adhesion, migration and survival (Mitra et al. 2005). In response to integrin stimulation, FAK is autophosphorylated at Tyr397, generating a binding site for the Src homology 2 (SH2) domain of SFKs such as Fyn (Cary et al. 1996). The recruited SFKs phosphorylate several additional FAK tyrosine residues to ensure full activation (Calalb et al. 1995). FAK-knockout mice exhibit embryonic lethality with defects in mesoderm development (Ilic et al. 1995). Neuron-specific FAK-knockout mice show abnormalities in axonal and dendritic morphology and synapse formation, indicating that FAK is critical for neuronal development in vivo (Beggs et al. 2003; Rico et al. 2004). FAK regulates neurite outgrowth in response to growth factors, integrin stimulation and neuronal guidance cues (Ivankovic-Dikic et al. 2000; Liu et al. 2004; Robles & Gomez 2006). However, the roles of FAK in the oligodendrocytic cell lineage are poorly understood, although FAK is expressed in primary oligodendrocytes (Kilpatrick et al. 2000).
Affinity purification with anti-phosphotyrosine antibody followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis is a powerful tool to identify tyrosine-phosphorylated proteins (Blagoev et al. 2004; Kratchmarova et al. 2005). In the present study, we attempted to identify tyrosine-phosphorylated proteins in differentiating oligodendrocytes using mass spectrometric analysis. We identified FAK as a substrate of Fyn in the rat CG4 oligodendrocyte cell line. Furthermore, we found that FAK was critical for outgrowth of processes from CG4 cells.
|
Results |
|---|
|
TopAbstractIntroductionResultsDiscussionExperimental proceduresReferences |
|---|
To identify tyrosine-phosphorylated proteins in oligodendrocytes, we used the rat-derived CG4 oligodendrocyte cell line. As shown in Fig. 1A, CG4 cells underwent differentiation from bipolar oligodendrocyte progenitor cells into immature oligodendrocytes extending multiple branched processes in glial-defined medium (GDM) (Louis et al. 1992). CG4 cells were induced to differentiate for 1, 2 or 3 days on poly-L-lysine (PLL)-coated dishes. Lysates of these cells were subjected to SDS-PAGE, and tyrosine-phosphorylated proteins were then visualized by immunoblotting with 4G10, an anti-phosphotyrosine monoclonal antibody (mAb) (Fig. 1B). We confirmed that tyrosine phosphorylation levels in CG4 cells were increased upon differentiation. The levels of activated SFKs also increased as monitored by anti-active SFKs [pY416 (SFK)] antibody (Bjorge et al. 2000). In addition, tyrosine phosphorylation in both anti-phosphotyrosine and anti-Fyn immunoprecipitates was enhanced during differentiation of CG4 cells (Fig. 1C). Within the latter immunoprecipitate a protein band that migrated with an approximate mass of 120 kDa (pp120) was prominent, and we speculated that pp120 might be a major substrate of Fyn.
|
|
We carried out immunoprecipitation with anti-FAK antibody and examined tyrosine phosphorylation of FAK during differentiation of CG4 cells. As expected, tyrosine phosphorylation of FAK was elevated 2 days after induction of differentiation (Fig. 3A). FAK is phosphorylated at multiple tyrosine residues including Tyr397, 407, 576, 577 and 861 upon activation in other cell types (Mitra et al. 2005). Tyr397 undergoes autophosphorylation in response to extracellular stimuli such as integrin. Tyr576 and Tyr577 are phosphorylated by SFKs, and phosphorylation of both tyrosine residues increases the catalytic activity of FAK. To determine which tyrosine phosphorylation sites are regulated during differentiation of CG4 cells, we used several phosphorylation site-specific antibodies against FAK. Phosphorylation of all tyrosine residues that we examined was enhanced upon differentiation (Fig. 3B).
|
Extracellular matrix components such as laminin activate SFKs through integrins on oligodendrocytes (Colognato et al. 2004; Liang et al. 2004). Because FAK is critical for integrin signaling, we tested whether laminin enhances tyrosine phosphorylation of FAK in CG4 cells. CG4 cells were induced to differentiate for 1 day on PLL- or laminin-coated dishes. We confirmed SFK activation in CG4 cells grown on laminin. Tyrosine phosphorylation of FAK was also enhanced in the presence of laminin (Fig. 3D), suggesting that the laminin–integrin pathway activates FAK during oligodendrocyte differentiation.
Suppression of laminin-induced process outgrowth by FAK knockdown in CG4 cells
To elucidate the function of FAK in oligodendrocytes, we established FAK-knockdown CG4 cells using retroviral vectors expressing an shRNA sequence against FAK. After retroviral infection, the infected cells were selected with puromycin. The expression level of FAK was significantly reduced by either of two independent shRNA constructs (Fig. 4A). To investigate whether FAK regulates process outgrowth in CG4 cells, we measured the sum total length of process on control and FAK-knockdown CG4 cells. In CG4 cells that had differentiated on PLL-coated dishes for 1 day, FAK-knockdown had no significant effect on process outgrowth (data not shown). Then, we examined process outgrowth on laminin, because laminin promotes process outgrowth of oligodendrocytes in a Fyn-dependent manner (Colognato et al. 2004). In CG4 cells that had differentiated on laminin-coated dishes for 1 day, the process outgrowth was significantly suppressed by FAK knockdown (Fig. 4B,C). These data were consistent with our observation that tyrosine phosphorylation of FAK in CG4 cells was enhanced by laminin (Fig. 3D). These results suggest that FAK is critical for laminin-induced process outgrowth in CG4 cells.
|
We next analyzed how FAK regulates the early biochemical events relevant to the process outgrowth in CG4 cells. Previous studies showed that SFKs are also regulated by FAK activity (Schlaepfer & Hunter 1997). Therefore, using immunoblotting with anti-pY416 (SFK) antibody, we examined whether knockdown of FAK expression alters the activity of SFKs in laminin-stimulated CG4 cells. Indeed, laminin-induced activation of SFKs was suppressed in CG4 cells expressing FAK-specific shRNA in comparison with those expressing control shRNA (Fig. 5A). The data suggested that SFKs and FAK are synergistically involved in laminin-induced process outgrowth.
|
Autophosphorylation of FAK at Tyr397 is required for laminin-induced process outgrowth in CG4 cells
Integrin clustering promotes FAK autophosphorylation at Tyr397. To examine the significance of the tyrosine phosphorylation event in process outgrowth of CG4 cells, we prepared retroviral RNAi-refractory FAK (rFAK) constructs. FAK-knockdown CG4 cells were infected with retrovirus expressing wild-type (WT) or Y397F mutant rFAK. Expression levels of rFAK WT and rFAK Y397F in FAK-knockdown cells were similar to that of FAK in the parental CG4 cells. Phosphorylation of Tyr397 occurred on rFAK WT but not rFAK Y397F (Fig. 6A). We measured the sum total length of processes on CG4 cells grown on laminin after differentiation for 1 day. Expression of rFAK WT efficiently restored process outgrowth in FAK-knockdown CG4 cells (Fig. 6B,C), confirming that suppression of process outgrowth by FAK knockdown was not due to off-target effects of the FAK shRNA. However, the rFAK Y397F mutant failed to rescue process outgrowth of CG4 cells. These results indicated that Tyr397 phosphorylation of FAK was needed for laminin-induced process outgrowth in CG4 cells.
|
|
Discussion |
|---|
|
TopAbstractIntroductionResultsDiscussionExperimental proceduresReferences |
|---|
We showed that laminin stimulation increased FAK tyrosine phosphorylation in differentiating CG4 cells (Fig. 3D). Moreover, FAK Tyr397 phosphorylation was critical for laminin-induced process outgrowth in CG4 cells (Fig. 6). In the CNS, 2 chain-containing laminins are found within axon tracts, and these laminins are required for oligodendroglial differentiation and survival (Colognato et al. 2002, 2004). In addition, 6 integrin-knockout mice exhibit loss of oligodendrocytes in the brain (Colognato et al. 2002), suggesting that signaling from extracellular matrix components such as laminin to integrins plays a critical role in oligodendrocyte development. Thus, laminin-induced FAK activation is likely to occur when an oligodendrocyte process contacts on axonal surface. In other cell types, FAK integrates growth-factor and integrin signals to promote cell migration (Sieg et al. 2000). It is reported that axonal neuregulin-1 engages ErbB2 and ErbB4, members of the ErbB-family of receptor tyrosine kinases, to regulate oligodendrocyte survival and differentiation (Fernandez et al. 2000; Kim et al. 2003; Sussman et al. 2005). In addition, co-stimulation with laminin and neuregulin-1 promotes the survival and differentiation of oligodendrocytes (Colognato et al. 2002). Therefore, FAK may be required for integration of integrin-neuregulin-1 signaling in oligodendrocytes.
To elucidate roles of FAK in myelination, analysis of conditional FAK-knockout mice would be informative. Recently, it is reported that Schwann cell-specific FAK-knockout mice show impaired myelination in the peripheral nervous system due to defects in proliferation of Schwann cells and radial sorting of axonal bundles (Grove et al. 2007). Analyses of oligodendrocyte lineage-specific FAK-knockout mice may clarify the roles of FAK in oligodendrocyte development and myelination in the CNS.
In neurons, FAK regulates neurite outgrowth induced by growth factors as well as integrins (Ivankovic-Dikic et al. 2000; Liu et al. 2004; Robles & Gomez 2006). Within these cells, FAK is localized at the growth cones of axons, and tyrosine phosphorylation of FAK in response to laminin is enriched at frontal tips of growth cones, in particular at point contacts. It is suggested that tyrosine phosphorylation of FAK at point contacts promotes neurite outgrowth by stabilizing the marginal structure on laminin (Robles & Gomez 2006). Distal tips of oligodendrocyte processes resemble growth cones of neurons (Fox et al. 2006), suggesting that the mechanisms underlying oligodendrocyte process outgrowth have several similarities to those of neurite outgrowth. Therefore, as in neurons, tyrosine phosphorylation of FAK may occur at the tips of the oligodendrocyte processes and lead to rapid process outgrowth.
In the present study, we showed that tyrosine phosphorylation of FAK was suppressed in Fyn-knockdown CG4 cells (Fig. 3C). Activities of SFKs were also reduced in FAK-knockdown CG4 cells (Fig. 5A). Therefore, as in other cell types (Liu et al. 2004; Mitra et al. 2005), FAK and Fyn appear to act cooperatively to evoke downstream signaling. Previous reports have suggested that Fyn regulates Rac1 and Cdc42 downstream of integrin in oligodendrocytes (Liang et al. 2004). In the present study, we showed FAK also to be involved in this pathway. FAK/SFK-mediated phosphorylation events activate Rac1 and Cdc42 in various cell types. Several guanine nucleotide exchange factors (GEFs) for Rac1 and Cdc42 are activated by SFK-mediated tyrosine phosphorylation. Tyrosine phosphorylation of Vav-family GEFs causes conformational changes, enhancing their GEF activities (Crespo et al. 1997). Tyrosine phosphorylation of FRG also elevates its GEF activity for Cdc42 (Miyamoto et al. 2003). In fibroblasts, FAK activates Rac1 through direct phosphorylation of ßPIX (Chang et al. 2007). In addition, a number of GTPase-activating proteins (GAPs) for Rho-family GTPases are also regulated by SFK-mediated tyrosine phosphorylation. Fyn-mediated tyrosine phosphorylation of p190RhoGAP elevates its GAP activity for Rho and over-expression of p190RhoGAP induce process outgrowth in oligodendrocytes (Wolf et al. 2001; Liang et al. 2004). Tyrosine phosphorylation of TCGAP by Fyn decreases its GAP activity for Cdc42 (Liu et al. 2006). Because critical GEFs and GAPs might differ according to cell types and signaling cascades, it is important to identify the GEFs and GAPs responsible for activation of Rac1 and Cdc42 during morphological differentiation of oligodendrocytes induced by integrin-Fyn/FAK signaling.
In the present study, we identified FAK as a Fyn substrate during differentiation of CG4 cells, but other tyrosine-phosphorylated proteins remain uncharacterized. Further identification and functional analyses of tyrosine-phosphorylated proteins in oligodendrocytes may clarify the precise signaling pathways that underlie oligodendrocyte development and myelination in the CNS.
|
Experimental procedures |
|---|
|
TopAbstractIntroductionResultsDiscussionExperimental proceduresReferences |
|---|
Expression plasmid pME-Fyn Y531F was described previously (Liu et al. 2006). For retroviral expression of a constitutively active form of Fyn, the cDNA encoding Fyn Y531F was cloned into pMX-puro. The plasmid for glutathione-S-transferase-Cdc42/Rac-interacting binding domain of Pak (GST-CRIB) was provided by C. Sasakawa (University of Tokyo, Tokyo, Japan). The small interfering RNA (siRNA) sequences specific for the rat Fyn and FAK mRNAs were determined with BLOCK-iT RNAi Designer (Invitrogen, Rockville, MD). The following target sequences were used: Fyn, 5'-GGAGACCATGTCAAACAT-3'; FAK#1, 5'-GGTCCAGACCAATCACTAT-3' and FAK#2, 5'-GCAGTTTGCCAACCTTAAT-3'. A control sequence (5'-TTCTCCGAACGTGTCACGT-3') with no significant homology to any mammalian gene sequence served as a non-silencing control. The annealed nucleotides were inserted into pSIREN-RetroQ (Takara Bio, Otsu, Japan). The cDNAs encoding mouse wild-type (WT) and Y397F mutant FAK were provided by D. Schlaepfer (The Scripps Research Institute, San Diego, CA). The RNAi-refractory mutant, which contained five silent mutations within the siRNA target sequence of FAK#2, was generated by PCR-based mutagenesis. The constructs were verified by DNA sequencing. For retroviral expression of FAK, these cDNAs were cloned into pMXs-neo.
Antibodies
Affinity-purified anti-FAK antibody was generated by immunizing a rabbit with a carboxyl-terminal fragment of FAK as an antigen (Ilic et al. 1995). Anti-Rac1 antibody was kindly provided by T. Takenawa (University of Tokyo). The following antibodies were purchased: anti-phosphotyrosine mAb, 4G10 (Millipore, Bedford, MA); anti--tubulin mAb (Sigma, St. Louis, MO); rabbit polyclonal anti-Fyn and anti-Cdc42 (Santa Cruz Biotechnology, Santa Cruz, CA); anti-pY416 (SFK) (Cell Signaling, Beverly, MA); and phosphorylation site-specific antibodies against pY397, pY407, pY576, pY577 and pY861 of FAK (Biosource, Camarillo, CA).
Cell culture and retroviral infection
Rat neuroblastoma B104 cells and Plat-E cells were maintained in Dulbecco's modified Eagle's medium containing 10% fetal bovine serum at 37 °C in 5% CO2. Rat oligodendroglial CG4 cells were maintained and differentiated on dishes coated with PLL (10 µg/mL) as described previously (Yonemasu et al. 1998). Briefly, CG4 cells were cultured in a glial-defined medium [GDM, 1/1 (v/v) mixture of Dulbecco's modified Eagle's medium and Ham's F12 supplemented with 5 mg/L insulin, 16.1 mg/L putrescine, 50 mg/L apo-transferrin, 4.6 mg/L D-galactose and 8 mg/L sodium selenite] containing 2% fetal bovine serum for proliferation. For maintenance of oligodendrocyte progenitor cells, CG4 cells were cultured in GDM containing 30% B104-conditioned medium. For differentiation, CG4 cells were cultured in GDM. Plat-E cells were transfected with pMX-puro, pMXs-neo or pSIREN-RetroQ plasmids with FuGENE6 Transfection Reagent (Roche, Mannheim, Germany), and the media containing the retrovirus were collected. CG4 cells were infected during the proliferating phase, and the infected cells were selected with puromycin (0.7 µg/mL) or G418 (700 µg/mL) (Liu et al. 2006).
Immunoprecipitation and immunoblotting
Cells were lysed for 1 h at 4 °C in a lysis buffer [TNE, 50 mM Tris–Cl (pH 7.4), 120 mM NaCl, 5 mM EDTA, 1% Nonidet P-40, 0.1% sodium deoxychorate, 1 mM Na3VO4 and aprotinin at 50 units/mL] and then centrifuged for 15 min at 21 000 g. Protein concentrations were measured with a BCATM protein assay kit (Pierce). For immunoprecipitation, pre-cleared lysates were incubated with appropriate antibodies and protein G-sepharose (GE Healthcare, Piscataway, NJ) for 2 h. Immunoprecipitates were washed 4 times with TNE buffer. Immunoprecipitates and lysates were resolved by SDS-PAGE and transferred to polyvinylidene difluoride membranes (Millipore). Membranes were blocked with Tris-buffered saline containing 0.1% Tween-20 and 2% bovine serum albumin and blotted with primary antibodies. Horseradish peroxidase- or alkaline phosphatase-conjugated secondary antibodies and Renaissance Plus Reagent (Perkin-Elmer, Boston, MA) or CDP-Star (Tropix, Bedford, MA) were used to visualize the immunoreactive proteins.
Large-scale immunoprecipitation and mass spectrometric analysis
For purification of tyrosine-phosphorylated proteins, CG4 cells were differentiated for 2 days at 37 °C. The harvested cells were solubilized in TNE buffer. Cell lysates (2 mg/mL, 2 mL) were incubated with 40 µg of anti-phosphotyrosine antibody 4G10 and protein A-sepharose (GE Healthcare) overnight at 4 °C. Immunocomplexes were precipitated, washed 5 times with TNE buffer and then boiled with SDS. The proteins were separated by SDS-PAGE and visualized by Coomassie Brilliant Blue staining and immunoblotting with 4G10. For the mass spectrometric analysis, bands visualized with Coomassie Brilliant Blue staining were excised from the gel and digested in the gel with trypsin (1 pmol/µL) for 12 h at 37 °C. The eluted peptides were loaded on the automated nanoflow liquid chromatograph (Dina) and tandem mass spectrometer (Q-TOF2). The peptide masses obtained with the LC-MS/MS analysis were searched against the non-redundant protein sequence database of the National Center for Biotechnology Information with the Mascot search engine (Matrix Science, London, UK).
Pull-down assay for Rac1 and Cdc42
To monitor Rac1 and Cdc42 activities, we performed the Rho effector pull-down assay as described previously (Liu et al. 2006). Briefly, cells were lysed for 5 min with ice-cold lysis buffer [50 mM Tris–Cl (pH 7.4), 100 mM NaCl, 2 mM MgCl2, 1% Nonidet P-40, 10% glycerol with aprotinin at 50 units/mL] and the lysates were then centrifuged 5 min at 21 000 g. The supernatants were incubated with 20 µg of GST-CRIB for 30 min. The beads were washed with lysis buffer and the bound proteins were resolved by SDS-PAGE and subjected to immunoblotting with anti-Rac1 or anti-Cdc42 antibody. For quantification, immunoreactive protein bands were analyzed by using the IMAGE J software (National Institutes of Health). Levels of active Rac1/Cdc42 were normalized to those of total Rac1/Cdc42. Data were statistically analyzed by Student's t-test. The difference was considered significant when P < 0.05.
Analysis of process outgrowth in CG4 cells
CG4 cells (5 x 104) were plated on 6-cm dishes coated with laminin (3 µg/mL) (Asahi Techno Glass), and induced to differentiate. The sum of all of the processes lengths for approximately 100 cells 1 day after differentiation was calculated with the IMAGE J software. Data were statistically analyzed by Student's t-test. The difference was considered significant when P < 0.05.
|
Acknowledgements |
|---|
|
Footnotes |
|---|
* Correspondence: E-mail: tyamamot{at}ims.u-tokyo.ac.jp
|
References |
|---|
|
TopAbstractIntroductionResultsDiscussionExperimental proceduresReferences |
|---|
Bjorge, J.D., Jakymiw, A. & Fujita, D.J. (2000) Selected glimpses into the activation and function of Src kinase. Oncogene 19, 5620–5635.[CrossRef][Medline]
Blagoev, B., Ong, S.E., Kratchmarova, I. & Mann, M. (2004) Temporal analysis of phosphotyrosine-dependent signaling networks by quantitative proteomics. Nat. Biotechnol. 22, 1139–1145.[CrossRef][Medline]
Calalb, M.B., Polte, T.R. & Hanks, S.K. (1995) Tyrosine phosphorylation of focal adhesion kinase at sites in the catalytic domain regulates kinase activity: a role for Src family kinases. Mol. Cell. Biol. 15, 954–963.[Abstract]
Cary, L.A., Chang, J.F. & Guan, J.L. (1996) Stimulation of cell migration by overexpression of focal adhesion kinase and its association with src and fyn. J. Cell Sci. 109, 1787–1794.[Abstract]
Chang, F., Lemmon, C.A., Park, D. & Romer, L.H. (2007) FAK potentiates Rac1 activation and localization to matrix adhesion sites: a role for ßPIX. Mol. Biol. Cell 18, 253–264.
Colognato, H., Baron, W., Avellana-Adalid, V., Relvas, J.B., Baron-Van, Evercooren, A., Georges-Labouesse, E. & ffrench-Constant, C. (2002) CNS integrins switch growth factor signalling to promote target-dependent survival. Nat. Cell Biol. 4, 833–841.[CrossRef][Medline]
Colognato, H., Ramachandrappa, S., Olsen, I.M. & ffrench-Constant, C. (2004) Integrins direct Src family kinases to regulate distinct phases of oligodendrocyte development. J. Cell Biol. 167, 365–375.
Crespo, P., Schuebel, K.E., Ostrom, A.A., Gutkind, J.S. & Bustelo, X.R. (1997) Phosphotyrosine-dependent activation of Rac-1 GDP/GTP exchange by the vav proto-oncogene product. Nature 385, 169–172.[CrossRef][Medline]
Fernandez, P.A., Tang, D.G., Cheng, L., Prochiantz, A., Mudge, A.W. & Raff, M.C. (2000) Evidence that axon-derived neuregulin promotes oligodendrocyte survival in the developing rat optic nerve. Neuron 28, 81–90.[CrossRef][Medline]
Fox, M.A., Afshari, F.S., Alexander, J.K., Colello, R.J. & Fuss, B. (2006) Growth conelike sensorimotor structures are characteristic features of postmigratory, premyelinating oligodendrocytes. Glia 53, 563–566.[CrossRef][Medline]
Goto, J., Tezuka, T., Nakazawa, T., Tsukamoto, N., Nakamura, T., Ajima, R., Yokoyama, K., Ohta, T., Ohki, M. & Yamamoto, T. (2004) Altered gene expression in the adult brain of fyn-deficient mice. Cell. Mol. Neurobiol. 24, 149–159.[CrossRef][Medline]
Grove, M., Komiyama, N.H., Nave, K.A., Grant, S.G., Sherman, D.L. & Brophy, P.J. (2007) FAK is required for axonal sorting by Schwann cells. J. Cell Biol. 176, 277–282.
Ilic, D., Furuta, Y., Kanazawa, S., Takeda, N., Sobue, K., Nakatsuji, N., Nomura, S., Fujimoto, J., Okada, M. & Yamamoto, T. (1995) Reduced cell motility and enhanced focal adhesion contact formation in cells from FAK-deficient mice. Nature 377, 539–544.[CrossRef][Medline]
Ivankovic-Dikic, I., Gronroos, E., Blaukat, A., Barth, B.U. & Dikic, I. (2000) Pyk2 and FAK regulate neurite outgrowth induced by growth factors and integrins. Nat. Cell Biol. 2, 574–581.[CrossRef][Medline]
Kilpatrick, T.J., Ortuno, D., Bucci, T., Lai, C. & Lemke, G. (2000) Rat oligodendroglia express c-met and focal adhesion kinase, protein tyrosine kinases implicated in regulating epithelial cell motility. Neurosci. Lett. 279, 5–8.[CrossRef][Medline]
Kim, J.Y., Sun, Q., Oglesbee, M. & Yoon, S.O. (2003) The role of ErbB2 signaling in the onset of terminal differentiation of oligodendrocytes in vivo. J. Neurosci. 23, 5561–5571.
Kratchmarova, I., Blagoev, B., Haack-Sorensen, M., Kassem, M. & Mann, M. (2005) Mechanism of divergent growth factor effects in mesenchymal stem cell differentiation. Science 308, 1472–1477.
Liang, X., Draghi, N.A. & Resh, M.D. (2004) Signaling from integrins to Fyn to Rho family GTPases regulates morphologic differentiation of oligodendrocytes. J. Neurosci. 24, 7140–7149.
Liu, G., Beggs, H., Jurgensen, C., Park, H.T., Tang, H., Gorski, J., Jones, K.R., Reichardt, L.F., Wu, J. & Rao, Y. (2004) Netrin requires focal adhesion kinase and Src family kinases for axon outgrowth and attraction. Nat. Neurosci. 7, 1222–1232.[CrossRef][Medline]
Liu, H., Nakazawa, T., Tezuka, T. & Yamamoto, T. (2006) Physical and functional interaction of Fyn tyrosine kinase with a brain-enriched Rho GTPase-activating protein TCGAP. J. Biol. Chem. 281, 23611–23619.
Louis, J.C., Magal, E., Muir, D., Manthorpe, M. & Varon, S. (1992) CG-4, a new bipotential glial cell line from rat brain, is capable of differentiating in vitro into either mature oligodendrocytes or type-2 astrocytes. J. Neurosci. Res. 31, 193–204.[CrossRef][Medline]
Lu, Z., Ku, L., Chen, Y. & Feng, Y. (2005) Developmental abnormalities of myelin basic protein expression in fyn knock-out brain reveal a role of Fyn in posttranscriptional regulation. J. Biol. Chem. 280, 389–395.
Mitra, S.K., Hanson, D.A. & Schlaepfer, D.D. (2005) Focal adhesion kinase: in command and control of cell motility. Nat. Rev. Mol. Cell Biol. 6, 56–68.[CrossRef][Medline]
Miyamoto, Y., Yamauchi, J. & Itoh, H. (2003) Src kinase regulates the activation of a novel FGD-1-related Cdc42 guanine nucleotide exchange factor in the signaling pathway from the endothelin A receptor to JNK. J. Biol. Chem. 278, 29890–29900.
Nakahara, J., Seiwa, C., Tan-Takeuchi, K., Gotoh, M., Kishihara, K., Ogawa, M., Asou, H. & Aiso, S. (2005) Involvement of CD45 in central nervous system myelination. Neurosci. Lett. 379, 116–121.[CrossRef][Medline]
Nakahara, J., Tan-Takeuchi, K., Seiwa, C., Gotoh, M., Kaifu, T., Ujike, A., Inui, M., Yagi, T., Ogawa, M., Aiso, S., Takai, T. & Asou, H. (2003) Signaling via immunoglobulin Fc receptors induces oligodendrocyte precursor cell differentiation. Dev. Cell 4, 841–852.[CrossRef][Medline]
Osterhout, D.J., Wolven, A., Wolf, R.M., Resh, M.D. & Chao, M.V. (1999) Morphological differentiation of oligodendrocytes requires activation of Fyn tyrosine kinase. J. Cell Biol. 145, 1209–1218.
Rico, B., Beggs, H.E., Schahin-Reed, D., Kimes, N., Schmidt, A. & Reichardt, L.F. (2004) Control of axonal branching and synapse formation by focal adhesion kinase. Nat. Neurosci. 7, 1059–1069.[CrossRef][Medline]
Robles, E. & Gomez, T.M. (2006) Focal adhesion kinase signaling at sites of integrin-mediated adhesion controls axon pathfinding. Nat. Neurosci. 9, 1274–1283.[CrossRef][Medline]
Schlaepfer, D.D. & Hunter, T. (1997) Focal adhesion kinase overexpression enhances ras-dependent integrin signaling to ERK2/mitogen-activated protein kinase through interactions with and activation of c-Src. J. Biol. Chem. 272, 13189–13195.
Sherman, D.L. & Brophy, P.J. (2005) Mechanisms of axon ensheathment and myelin growth. Nat. Rev. Neurosci. 6, 683–690.[CrossRef][Medline]
Sieg, D.J., Hauck, C.R., Ilic, D., Klingbeil, C.K., Schaefer, E., Damsky, C.H. & Schlaepfer, D.D. (2000) FAK integrates growth-factor and integrin signals to promote cell migration. Nat. Cell Biol. 2, 249–256.[CrossRef][Medline]
Sussman, C.R., Vartanian, T. & Miller, R.H. (2005) The ErbB4 neuregulin receptor mediates suppression of oligodendrocyte maturation. J. Neurosci. 25, 5757–5762.
Taniguchi, S., Liu, H., Nakazawa, T., Yokoyama, K., Tezuka, T. & Yamamoto, T. (2003) p250GAP, a neural RhoGAP protein, is associated with and phosphorylated by Fyn. Biochem. Biophys. Res. Commun. 306, 151–155.[CrossRef][Medline]
Umemori, H., Kadowaki, Y., Hirosawa, K., Yoshida, Y., Hironaka, K., Okano, H. & Yamamoto, T. (1999) Stimulation of myelin basic protein gene transcription by Fyn tyrosine kinase for myelination. J. Neurosci. 19, 1393–1397.
Umemori, H., Sato, S., Yagi, T., Aizawa, S. & Yamamoto, T. (1994) Initial events of myelination involve Fyn tyrosine kinase signaling. Nature 367, 572–576.[CrossRef][Medline]
Umemori, H., Wanaka, A., Kato, H., Takeuchi, M., Tohyama, M. & Yamamoto, T. (1992) Specific expressions of Fyn and Lyn, lymphocyte antigen receptor-associated tyrosine kinases, in the central nervous system. Brain Res. Mol. Brain Res. 16, 303–310.[Medline]
Wolf, R.M., Wilkes, J.J., Chao, M.V. & Resh, M.D. (2001) Tyrosine phosphorylation of p190 RhoGAP by Fyn regulates oligodendrocyte differentiation. J. Neurobiol. 49, 62–78.[CrossRef][Medline]
Yonemasu, T., Nakahira, K., Okumura, S., Kagawa, T., Espinosa de los Monteros, A., de Vellis, J. & Ikenaka, K. (1998) Proximal promoter region is sufficient to regulate tissue-specific expression of UDP-galactose: ceramide galactosyltransferase gene. J. Neurosci. Res. 52, 757–765.[CrossRef][Medline]
Received: 26 May 2007
Accepted: 5 August 2007
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | ADVANCED SEARCH | TABLE OF CONTENTS |
