title: Coordination between extrinsic extracellular matrix cues and intrinsic responses to orient the centrosome in polarizing cerebellar granule neurons.
abstract: Successful axon targeting during development is critically dependent on directionality of axon extension and requires coordination between the extrinsic cues that provide spatial information to the axon and the intrinsic responses that regulate structural specification of the axon during neuronal polarization. How these responses are coordinated is unclear but are known to involve aligning the centrosome with the base of the emerging axon. We have used a novel in vitro micropatterning assay that spatially segregates the extrinsic cues used by polarizing cerebellar granule cells to orient axon extension and used it to investigate the signaling mechanisms responsible for coordinating centrosome positioning with intrinsic responses. The results show that, when laminin and/or vitronectin are used as spatially restricted cues in association with substrate-associated sonic hedgehog, they are sufficient to induce cell cycle arrest, that laminin and vitronectin then induce integrin-mediated signaling that upregulates phosphoinositide-3 kinase and PKC function to produce phosphatidylinositol 3,4,5-trisphosphate (PIP3) that is associated with the centrosome, that this PIP3 can interact with PKC-phosphorylated growth-associated protein GAP-43, and that PKC-phosphorylated GAP-43 in turn is required for positioning Par6, Cdc42, and IQGAP1, all intrinsic response components, in proximity to the centrosome, such that, in the absence of GAP-43, they are mislocalized and microtubules are not oriented appropriately. We conclude from these results that GAP-43 plays an important role in coordinating extrinsic signaling and intrinsic responses in polarizing cerebellar granule neurons.
authors.affiliation: National Brain Research Center, Manesar, Haryana 122 050, India.
authors.forename: Shailesh Kumar
authors.initials: SK
authors.lastname: Gupta
authors.forename: Karina F
authors.initials: KF
authors.lastname: Meiri
authors.forename: Kashif
authors.initials: K
authors.lastname: Mahfooz
authors.forename: Upasna
authors.initials: U
authors.lastname: Bharti
authors.forename: Shyamala
authors.initials: S
authors.lastname: Mani
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D018385:Centrosome / Q000502:physiology*; D002531:Cerebellum / Q000166:cytology* / Q000254:growth & development; D004622:Embryo, Mammalian; D005109:Extracellular Matrix / Q000502:physiology*; D019922:GAP-43 Protein / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000235:genetics; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism; D066298:In Vitro Techniques; D007797:Laminin / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000166:cytology* / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D011493:Protein Kinase C / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D019096:Vitronectin / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020703:ras GTPase-Activating Proteins / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D019922:GAP-43 Protein; D053823:Hedgehog Proteins; C101203:IQ motif containing GTPase activating protein 1; D007797:Laminin; D009419:Nerve Tissue Proteins; C518597:Par6 protein, mouse; D034741:RNA, Small Interfering; C465570:Shh protein, mouse; D019096:Vitronectin; C485184:enhanced green fluorescent protein; D020703:ras GTPase-Activating Proteins; D049452:Green Fluorescent Proteins; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D020764:cdc42 GTP-Binding Protein