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Integrins direct Src family kinases to regulate distinct phases of oligodendrocyte development.

Colognato H, Ramachandrappa S, Olsen IM, ffrench-Constant C - J. Cell Biol. (2004)

Bottom Line: Specific integrins expressed on oligodendrocytes, the myelin-forming cells of the central nervous system, promote either differentiation and survival or proliferation by amplification of growth factor signaling.Fyn associates with alpha6beta1 and is required to amplify platelet-derived growth factor survival signaling, to promote myelin membrane formation, and to switch neuregulin signaling from a phosphatidylinositol 3-kinase to a mitogen-activated protein kinase pathway (thereby changing the response from proliferation to differentiation).However, earlier in the lineage Lyn, not Fyn, is required to drive alphaVbeta3-dependent progenitor proliferation.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, University of Cambridge, Cambridge CB21QP, England, UK. colognato@pharm.sunysb.edu

ABSTRACT
Specific integrins expressed on oligodendrocytes, the myelin-forming cells of the central nervous system, promote either differentiation and survival or proliferation by amplification of growth factor signaling. Here, we report that the Src family kinases (SFKs) Fyn and Lyn regulate each of these distinct integrin-driven behaviors. Fyn associates with alpha6beta1 and is required to amplify platelet-derived growth factor survival signaling, to promote myelin membrane formation, and to switch neuregulin signaling from a phosphatidylinositol 3-kinase to a mitogen-activated protein kinase pathway (thereby changing the response from proliferation to differentiation). However, earlier in the lineage Lyn, not Fyn, is required to drive alphaVbeta3-dependent progenitor proliferation. The two SFKs respond to integrin ligation by different mechanisms: Lyn, by increased autophosphorylation of a catalytic tyrosine; and Fyn, by reduced Csk phosphorylation of the inhibitory COOH-terminal tyrosine. These findings illustrate how different SFKs can act as effectors for specific cell responses during development within a single cell lineage, and, furthermore, provide a molecular mechanism to explain similar region-specific hypomyelination in laminin- and Fyn-deficient mice.

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SFK associations with integrins and growth factors. (A) Newly formed oligodendrocytes immunostained with antibodies against Fyn (red) and α6β1 integrin (green). Merged panel is shown on the right. (B) Oligodendrocyte lysates from cells differentiated on ECM substrates in the presence or absence of PDGF or NRG. Western blot on α6 integrin antibody immunoprecipitation complexes to detect Fyn. (C) Western blot on Fyn antibody immunoprecipitation complexes to detect ErbB4 NRG receptor subunit. (D) Western blot on PDGFαR antibody immunoprecipitation complexes to detect Lyn. (E) Western blots on Lyn antibody immunoprecipitation complexes to detect the β3 integrin subunit.
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fig7: SFK associations with integrins and growth factors. (A) Newly formed oligodendrocytes immunostained with antibodies against Fyn (red) and α6β1 integrin (green). Merged panel is shown on the right. (B) Oligodendrocyte lysates from cells differentiated on ECM substrates in the presence or absence of PDGF or NRG. Western blot on α6 integrin antibody immunoprecipitation complexes to detect Fyn. (C) Western blot on Fyn antibody immunoprecipitation complexes to detect ErbB4 NRG receptor subunit. (D) Western blot on PDGFαR antibody immunoprecipitation complexes to detect Lyn. (E) Western blots on Lyn antibody immunoprecipitation complexes to detect the β3 integrin subunit.

Mentions: Having shown that Lyn and Fyn regulate proliferation and survival/differentiation, respectively, we asked whether each SFK was associated with the integrin–growth factor receptor complexes responsible for these different stages of oligodendroglial development. Using immunofluorescence microscopy, we detected α6β1 and Fyn in newly formed oligodendrocytes in an overlapping distribution (Fig. 7 A). Next, detergent lysates of newly formed oligodendrocytes grown on PDL, Lm2, and FN in the presence or absence of growth factors were evaluated by immunoprecipitation for the formation of protein complexes (Fig. 7, B–E). Antibodies specific for the α6 integrin subunit isolated complexes containing Fyn, but not Lyn, and the α6β1–Fyn association was independent of substrate or growth factor stimuli (Fig. 7 B). Immunoprecipitations using Fyn antibodies also revealed a potential association between Fyn and the ErbB4 NRG receptor subunit (Fig. 7 C). This association was difficult to detect but, interestingly, was only observed in cells treated with NRG on non-integrin substrates. PDGFαR immunoprecipitations revealed an association between PDGFαR and Lyn that, in the absence of PDGF, was most robust on FN but, in the presence of PDGF, was also observed in cells grown on PDL or Lm2 (Fig. 7 D). No association between Fyn and PDGFαR was observed (unpublished data). Lyn immunoprecipitations revealed an association between Lyn, but not Fyn, and the αVβ3 integrin that was also enhanced by FN but, in contrast to the Lyn–PDGFαR association, was not detected after PDGF treatment (Fig. 7 E).


Integrins direct Src family kinases to regulate distinct phases of oligodendrocyte development.

Colognato H, Ramachandrappa S, Olsen IM, ffrench-Constant C - J. Cell Biol. (2004)

SFK associations with integrins and growth factors. (A) Newly formed oligodendrocytes immunostained with antibodies against Fyn (red) and α6β1 integrin (green). Merged panel is shown on the right. (B) Oligodendrocyte lysates from cells differentiated on ECM substrates in the presence or absence of PDGF or NRG. Western blot on α6 integrin antibody immunoprecipitation complexes to detect Fyn. (C) Western blot on Fyn antibody immunoprecipitation complexes to detect ErbB4 NRG receptor subunit. (D) Western blot on PDGFαR antibody immunoprecipitation complexes to detect Lyn. (E) Western blots on Lyn antibody immunoprecipitation complexes to detect the β3 integrin subunit.
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Related In: Results  -  Collection

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fig7: SFK associations with integrins and growth factors. (A) Newly formed oligodendrocytes immunostained with antibodies against Fyn (red) and α6β1 integrin (green). Merged panel is shown on the right. (B) Oligodendrocyte lysates from cells differentiated on ECM substrates in the presence or absence of PDGF or NRG. Western blot on α6 integrin antibody immunoprecipitation complexes to detect Fyn. (C) Western blot on Fyn antibody immunoprecipitation complexes to detect ErbB4 NRG receptor subunit. (D) Western blot on PDGFαR antibody immunoprecipitation complexes to detect Lyn. (E) Western blots on Lyn antibody immunoprecipitation complexes to detect the β3 integrin subunit.
Mentions: Having shown that Lyn and Fyn regulate proliferation and survival/differentiation, respectively, we asked whether each SFK was associated with the integrin–growth factor receptor complexes responsible for these different stages of oligodendroglial development. Using immunofluorescence microscopy, we detected α6β1 and Fyn in newly formed oligodendrocytes in an overlapping distribution (Fig. 7 A). Next, detergent lysates of newly formed oligodendrocytes grown on PDL, Lm2, and FN in the presence or absence of growth factors were evaluated by immunoprecipitation for the formation of protein complexes (Fig. 7, B–E). Antibodies specific for the α6 integrin subunit isolated complexes containing Fyn, but not Lyn, and the α6β1–Fyn association was independent of substrate or growth factor stimuli (Fig. 7 B). Immunoprecipitations using Fyn antibodies also revealed a potential association between Fyn and the ErbB4 NRG receptor subunit (Fig. 7 C). This association was difficult to detect but, interestingly, was only observed in cells treated with NRG on non-integrin substrates. PDGFαR immunoprecipitations revealed an association between PDGFαR and Lyn that, in the absence of PDGF, was most robust on FN but, in the presence of PDGF, was also observed in cells grown on PDL or Lm2 (Fig. 7 D). No association between Fyn and PDGFαR was observed (unpublished data). Lyn immunoprecipitations revealed an association between Lyn, but not Fyn, and the αVβ3 integrin that was also enhanced by FN but, in contrast to the Lyn–PDGFαR association, was not detected after PDGF treatment (Fig. 7 E).

Bottom Line: Specific integrins expressed on oligodendrocytes, the myelin-forming cells of the central nervous system, promote either differentiation and survival or proliferation by amplification of growth factor signaling.Fyn associates with alpha6beta1 and is required to amplify platelet-derived growth factor survival signaling, to promote myelin membrane formation, and to switch neuregulin signaling from a phosphatidylinositol 3-kinase to a mitogen-activated protein kinase pathway (thereby changing the response from proliferation to differentiation).However, earlier in the lineage Lyn, not Fyn, is required to drive alphaVbeta3-dependent progenitor proliferation.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, University of Cambridge, Cambridge CB21QP, England, UK. colognato@pharm.sunysb.edu

ABSTRACT
Specific integrins expressed on oligodendrocytes, the myelin-forming cells of the central nervous system, promote either differentiation and survival or proliferation by amplification of growth factor signaling. Here, we report that the Src family kinases (SFKs) Fyn and Lyn regulate each of these distinct integrin-driven behaviors. Fyn associates with alpha6beta1 and is required to amplify platelet-derived growth factor survival signaling, to promote myelin membrane formation, and to switch neuregulin signaling from a phosphatidylinositol 3-kinase to a mitogen-activated protein kinase pathway (thereby changing the response from proliferation to differentiation). However, earlier in the lineage Lyn, not Fyn, is required to drive alphaVbeta3-dependent progenitor proliferation. The two SFKs respond to integrin ligation by different mechanisms: Lyn, by increased autophosphorylation of a catalytic tyrosine; and Fyn, by reduced Csk phosphorylation of the inhibitory COOH-terminal tyrosine. These findings illustrate how different SFKs can act as effectors for specific cell responses during development within a single cell lineage, and, furthermore, provide a molecular mechanism to explain similar region-specific hypomyelination in laminin- and Fyn-deficient mice.

Show MeSH
Related in: MedlinePlus