title: APC and GSK-3beta are involved in mPar3 targeting to the nascent axon and establishment of neuronal polarity.
abstract: In developing hippocampal neurons in culture, the evolutionarily conserved polarity complex mPar3/mPar6/aPKC selectively accumulates at the tip of one, and only one, of the immature neurites of a neuron and thus specifies the axon and generates neuronal polarity. How mPar3/mPar6 is enriched at the tip of the nascent axon, but not the dendrites, is not fully understood. Here, we report that mPar3 forms a complex with adenomatous polyposis coli (APC) and kinesin superfamily (KIF) 3A, proteins that move along microtubules. In polarizing hippocampal neurons, APC selectively accumulates at the nascent axon tip and colocalizes with mPar3. Expression of dominant-negative C terminus deletion mutants of APC or ectopic expression of APC leads to dislocalization of mPar3 and defects in axon specification and neuronal polarity. In addition to spatial polarization of APC, the selective inactivation of the GSK-3beta activity at the nascent axon tip is required for mPar3 targeting and polarization and establishing neuronal polarity. These results suggest that mPar3 is polarized in developing neurons through APC- and kinesin-mediated transport to the plus ends of rapidly growing microtubules at the nascent axon tip, a process that involves a spatially regulated GSK-3beta activity.
authors.affiliation: Departments of Physiology and Biochemistry, Howard Hughes Medical Institute, University of California at San Francisco, 1550 4th Street, San Francisco, CA 94143-0725, USA.
authors.forename: Song-Hai
authors.initials: SH
authors.lastname: Shi
authors.forename: Tong
authors.initials: T
authors.lastname: Cheng
authors.forename: Lily Yeh
authors.initials: LY
authors.lastname: Jan
authors.forename: Yuh-Nung
authors.initials: YN
authors.lastname: Jan
mesh_terms: D025601:Adenomatous Polyposis Coli Protein / Q000378:metabolism*; D000818:Animals; D001369:Axons / Q000378:metabolism*; D019556:COS Cells; D002352:Carrier Proteins / Q000378:metabolism*; D016764:Cell Polarity / Q000502:physiology*; D002522:Chlorocebus aethiops; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism*; D015151:Immunoblotting; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D016547:Kinesins / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins; D051381:Rats
chemical_list: D025601:Adenomatous Polyposis Coli Protein; D002352:Carrier Proteins; C490201:Kif3a protein, rat; D009419:Nerve Tissue Proteins; C472451:Pard3 protein, rat; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D038362:Glycogen Synthase Kinase 3; D016547:Kinesins