title: KIF21A-mediated axonal transport and selective endocytosis underlie the polarized targeting of NCKX2.
abstract: We have previously shown that K(+)-dependent Na(+)/Ca(2+) exchanger (NCKX) is a major calcium clearance mechanism at the large axon terminals of central neurons, whereas their somata display little NCKX activity. We investigated mechanisms underlying the axonal polarization of NCKX2 in rat hippocampal neurons. We identified NCKX2 as the first neuron-specific cargo molecule of kinesin family member 21A (KIF21A). The intracellular loop of NCKX2 specifically interacted with the WD-40 repeats, a putative cargo-binding domain, of KIF21A. Dominant-negative mutant or depletion of KIF21A inhibited the transport of NCKX2-GFP to axon fibers. Knockdown of KIF21A caused calcium dysregulation at axonal boutons but not at somatodendritic regions. Despite the axonal polarization of the NCKX activity, both somatodendritic and axonal regions were immunoreactive to NCKX2. The surface expression of NCKX2 revealed by live-cell immunocytochemistry, however, displayed highly polarized distribution to the axon. Inhibition of endocytosis increased the somatodendritic surface NCKX2 and thus abolished the axonal polarization of surface NCKX2. These results indicate that KIF21A-mediated axonal transport and selective somatodendritic endocytosis underlie the axonal polarized surface expression of NCKX2.
authors.affiliation: Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, South Korea.
authors.forename: Kyu-Hee
authors.initials: KH
authors.lastname: Lee
authors.forename: Jae Sung
authors.initials: JS
authors.lastname: Lee
authors.forename: Doyun
authors.initials: D
authors.lastname: Lee
authors.forename: Dae-Hyun
authors.initials: DH
authors.lastname: Seog
authors.forename: Jonathan
authors.initials: J
authors.lastname: Lytton
authors.forename: Won-Kyung
authors.initials: WK
authors.lastname: Ho
authors.forename: Suk-Ho
authors.initials: SH
authors.lastname: Lee
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D018920:Coculture Techniques; D003712:Dendrites / Q000378:metabolism; D034284:Dynamin I / Q000235:genetics / Q000378:metabolism; D004558:Electric Stimulation; D004705:Endocytosis / Q000235:genetics / Q000502:physiology*; D005786:Gene Expression Regulation / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D047468:Immunoprecipitation; D016547:Kinesins / Q000235:genetics / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009457:Neuroglia / Q000502:physiology; D009474:Neurons / Q000166:cytology* / Q000378:metabolism; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D021381:Protein Transport / Q000235:genetics; D034622:RNA Interference / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D019831:Sodium-Calcium Exchanger / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: C119023:KIF21A protein, human; C489787:MAP2 protein, rat; D008869:Microtubule-Associated Proteins; D019831:Sodium-Calcium Exchanger; D049452:Green Fluorescent Proteins; C074530:potassium-dependent sodium-calcium exchanger; D034284:Dynamin I; D016547:Kinesins; D002118:Calcium