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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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Fyn is required for a laminin-mediated switch in NRG signaling and for integrin activation to increase survival. (A) Survival of newly formed SFK-depleted oligodendrocytes in the presence of the PI3K pathway signaling inhibitor wortmannin (hatched bars), the MAPK pathway signaling inhibitor PD098059 (light gray bars), or DMSO control (black bars). Lm2 switches NRG-mediated survival from PI3K-sensitive to PI3K-insensitive, and Fyn depletion, but not Lyn depletion, abolishes this effect. Error bars represent SD. (B) Oligodendrocytes treated for 30 min with NRG. PhosphoERK is enhanced by Lm2 in control cells, but not in Fyn(−) cells. (C) Survival of newly formed SFK-depleted oligodendrocytes in the presence (light gray bars) or absence (dark gray bars) of integrin-activating manganese. Integrin activation using manganese increased NRG-mediated survival, and this increase was lost in the absence of Fyn, but not of other SFKs. Error bars represent SD.
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fig5: Fyn is required for a laminin-mediated switch in NRG signaling and for integrin activation to increase survival. (A) Survival of newly formed SFK-depleted oligodendrocytes in the presence of the PI3K pathway signaling inhibitor wortmannin (hatched bars), the MAPK pathway signaling inhibitor PD098059 (light gray bars), or DMSO control (black bars). Lm2 switches NRG-mediated survival from PI3K-sensitive to PI3K-insensitive, and Fyn depletion, but not Lyn depletion, abolishes this effect. Error bars represent SD. (B) Oligodendrocytes treated for 30 min with NRG. PhosphoERK is enhanced by Lm2 in control cells, but not in Fyn(−) cells. (C) Survival of newly formed SFK-depleted oligodendrocytes in the presence (light gray bars) or absence (dark gray bars) of integrin-activating manganese. Integrin activation using manganese increased NRG-mediated survival, and this increase was lost in the absence of Fyn, but not of other SFKs. Error bars represent SD.

Mentions: Laminin switches the preferred signaling pathways activated during NRG-mediated survival (Colognato et al., 2002). Thus, on nonlaminin substrates, survival is sensitive to PI3K inhibition but insensitive to MAPK inhibition. This pattern is reversed by Lm2, such that survival is insensitive to PI3K inhibition but sensitive to MAPK inhibition (Fig. 5 A). Here, we observed that the laminin-driven switch in NRG signaling did not occur in Fyn-deficient cells, whereas Lyn-deficient cells remained able to switch. Wortmannin treatment of Fyn(−) cells grown with NRG on Lm2 significantly reduced survival (**, P < 0.01) compared with control and Lyn-depleted cells grown on Lm2 (Fig. 5 A). Furthermore, Fyn depletion caused the cells to become less sensitive to the MEK inhibitor PD098059 (Fig. 5 A). In addition, cells grown on Lm2 and treated with NRG show enhanced phosphorylation of extracellular signal–related kinase (ERK), yet do not amplify phosphorylation of Akt. Using a modified electroporation technique to obtain a high percentage of siRNA-positive cells (∼50%), Western blots of oligodendrocyte lysates revealed that Fyn-depleted cells treated with NRG were unable to amplify ERK phosphorylation (Fig. 5 B).


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)

Fyn is required for a laminin-mediated switch in NRG signaling and for integrin activation to increase survival. (A) Survival of newly formed SFK-depleted oligodendrocytes in the presence of the PI3K pathway signaling inhibitor wortmannin (hatched bars), the MAPK pathway signaling inhibitor PD098059 (light gray bars), or DMSO control (black bars). Lm2 switches NRG-mediated survival from PI3K-sensitive to PI3K-insensitive, and Fyn depletion, but not Lyn depletion, abolishes this effect. Error bars represent SD. (B) Oligodendrocytes treated for 30 min with NRG. PhosphoERK is enhanced by Lm2 in control cells, but not in Fyn(−) cells. (C) Survival of newly formed SFK-depleted oligodendrocytes in the presence (light gray bars) or absence (dark gray bars) of integrin-activating manganese. Integrin activation using manganese increased NRG-mediated survival, and this increase was lost in the absence of Fyn, but not of other SFKs. Error bars represent SD.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172535&req=5

fig5: Fyn is required for a laminin-mediated switch in NRG signaling and for integrin activation to increase survival. (A) Survival of newly formed SFK-depleted oligodendrocytes in the presence of the PI3K pathway signaling inhibitor wortmannin (hatched bars), the MAPK pathway signaling inhibitor PD098059 (light gray bars), or DMSO control (black bars). Lm2 switches NRG-mediated survival from PI3K-sensitive to PI3K-insensitive, and Fyn depletion, but not Lyn depletion, abolishes this effect. Error bars represent SD. (B) Oligodendrocytes treated for 30 min with NRG. PhosphoERK is enhanced by Lm2 in control cells, but not in Fyn(−) cells. (C) Survival of newly formed SFK-depleted oligodendrocytes in the presence (light gray bars) or absence (dark gray bars) of integrin-activating manganese. Integrin activation using manganese increased NRG-mediated survival, and this increase was lost in the absence of Fyn, but not of other SFKs. Error bars represent SD.
Mentions: Laminin switches the preferred signaling pathways activated during NRG-mediated survival (Colognato et al., 2002). Thus, on nonlaminin substrates, survival is sensitive to PI3K inhibition but insensitive to MAPK inhibition. This pattern is reversed by Lm2, such that survival is insensitive to PI3K inhibition but sensitive to MAPK inhibition (Fig. 5 A). Here, we observed that the laminin-driven switch in NRG signaling did not occur in Fyn-deficient cells, whereas Lyn-deficient cells remained able to switch. Wortmannin treatment of Fyn(−) cells grown with NRG on Lm2 significantly reduced survival (**, P < 0.01) compared with control and Lyn-depleted cells grown on Lm2 (Fig. 5 A). Furthermore, Fyn depletion caused the cells to become less sensitive to the MEK inhibitor PD098059 (Fig. 5 A). In addition, cells grown on Lm2 and treated with NRG show enhanced phosphorylation of extracellular signal–related kinase (ERK), yet do not amplify phosphorylation of Akt. Using a modified electroporation technique to obtain a high percentage of siRNA-positive cells (∼50%), Western blots of oligodendrocyte lysates revealed that Fyn-depleted cells treated with NRG were unable to amplify ERK phosphorylation (Fig. 5 B).

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