title: Release of kinesin from vesicles by hsc70 and regulation of fast axonal transport.
abstract: The nature of kinesin interactions with membrane-bound organelles and mechanisms for regulation of kinesin-based motility have both been surprisingly difficult to define. Most kinesin is recovered in supernatants with standard protocols for purification of motor proteins, but kinesin recovered on membrane-bound organelles is tightly bound. Partitioning of kinesin between vesicle and cytosolic fractions is highly sensitive to buffer composition. Addition of either N-ethylmaleimide or EDTA to homogenization buffers significantly increased the fraction of kinesin bound to organelles. Given that an antibody against kinesin light chain tandem repeats also releases kinesin from vesicles, these observations indicated that specific cytoplasmic factors may regulate kinesin release from membranes. Kinesin light tandem repeats contain DnaJ-like motifs, so the effects of hsp70 chaperones were evaluated. Hsc70 released kinesin from vesicles in an MgATP-dependent and N-ethylmaleimide-sensitive manner. Recombinant kinesin light chains inhibited kinesin release by hsc70 and stimulated the hsc70 ATPase. Hsc70 actions may provide a mechanism to regulate kinesin function by releasing kinesin from cargo in specific subcellular domains, thereby effecting delivery of axonally transported materials.
authors.affiliation: Department of Cell Biology and Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9039, USA.
authors.forename: M Y
authors.initials: MY
authors.lastname: Tsai
authors.forename: G
authors.initials: G
authors.lastname: Morfini
authors.forename: G
authors.initials: G
authors.lastname: Szebenyi
authors.forename: S T
authors.initials: ST
authors.lastname: Brady
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001370:Axonal Transport / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D006224:Cricetinae; D003902:Detergents; D004072:Digitonin; D004492:Edetic Acid; D005033:Ethylmaleimide; D049452:Green Fluorescent Proteins; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D016547:Kinesins / Q000302:isolation & purification / Q000378:metabolism*; D008164:Luminescent Proteins / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D017830:Octoxynol; D015388:Organelles / Q000378:metabolism; D013347:Subcellular Fractions
chemical_list: D002352:Carrier Proteins; D003902:Detergents; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C494372:Hspa8 protein, mouse; D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins; D017830:Octoxynol; D004492:Edetic Acid; D016547:Kinesins; D004072:Digitonin; D005033:Ethylmaleimide