title: Protein kinase Cα and integrin-linked kinase mediate the negative axon guidance effects of Sonic hedgehog.
abstract: In addition to its role as a morphogen, Sonic hedgehog (Shh) has also been shown to function as a guidance factor that directly acts on the growth cones of various types of axons. However, the noncanonical signaling pathways that mediate the guidance effects of Shh protein remain poorly understood. We demonstrate that a novel signaling pathway consisting of protein kinase Cα (PKCα) and integrin-linked kinase (ILK) mediates the negative guidance effects of high concentration of Shh on retinal ganglion cell (RGC) axons. Shh rapidly increased Ca(2+) level and activated PKCα and ILK in the growth cones of RGC axons. By in vitro kinase assay, PKCα was found to directly phosphorylate ILK on threonine-173 and -181. Inhibition of PKCα or expression of a mutant ILK with the PKCα phosphorylation sites mutated (ILK-DM), abolished the Shh-induced macropinocytosis, growth cone collapse and repulsive axon turning. In vivo, expression of a dominant negative PKCα or ILK-DM disrupted RGC axon pathfinding at the optic chiasm but not the projection toward the optic disk, supporting that this signaling pathway plays a specific role in Shh-mediated negative guidance effects.
authors.affiliation: Department of Medicine and Cell Biology, Program in Neuroscience, University of Massachusetts Medical School, Worcester, MA 01605, USA. daorong.guo@umassmed.edu
authors.forename: Daorong
authors.initials: D
authors.lastname: Guo
authors.forename: Clive
authors.initials: C
authors.lastname: Standley
authors.forename: Karl
authors.initials: K
authors.lastname: Bellve
authors.forename: Kevin
authors.initials: K
authors.lastname: Fogarty
authors.forename: Zheng-Zheng
authors.initials: ZZ
authors.lastname: Bao
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D001369:Axons / Q000201:enzymology* / Q000502:physiology; D001578:Benzopyrans / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002642:Chick Embryo; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020439:Growth Cones / Q000201:enzymology; D053823:Hedgehog Proteins / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation; D051571:Protein Kinase C-alpha / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000201:enzymology; D013912:Threonine; D000099200:Scaffold Protein ILK
chemical_list: D000098:Acetophenones; D001578:Benzopyrans; D002118:Calcium; D004791:Enzyme Inhibitors; D053823:Hedgehog Proteins; D051571:Protein Kinase C-alpha; D017346:Protein Serine-Threonine Kinases; D013912:Threonine; D000099200:Scaffold Protein ILK; C085746:rottlerin