title: Conventional kinesin holoenzymes are composed of heavy and light chain homodimers.
abstract: Conventional kinesin is a major microtubule-based motor protein responsible for anterograde transport of various membrane-bounded organelles (MBO) along axons. Structurally, this molecular motor protein is a tetrameric complex composed of two heavy (kinesin-1) chains and two light chain (KLC) subunits. The products of three kinesin-1 (kinesin-1A, -1B, and -1C, formerly KIF5A, -B, and -C) and two KLC (KLC1, KLC2) genes are expressed in mammalian nervous tissue, but the functional significance of this subunit heterogeneity remains unknown. In this work, we examine all possible combinations among conventional kinesin subunits in brain tissue. In sharp contrast with previous reports, immunoprecipitation experiments here demonstrate that conventional kinesin holoenzymes are formed of kinesin-1 homodimers. Similar experiments confirmed previous findings of KLC homodimerization. Additionally, no specificity was found in the interaction between kinesin-1s and KLCs, suggesting the existence of six variant forms of conventional kinesin, as defined by their gene product composition. Subcellular fractionation studies indicate that such variants associate with biochemically different MBOs and further suggest a role of kinesin-1s in the targeting of conventional kinesin holoenzymes to specific MBO cargoes. Taken together, our data address the combination of subunits that characterize endogenous conventional kinesin. Findings on the composition and subunit organization of conventional kinesin as described here provide a molecular basis for the regulation of axonal transport and delivery of selected MBOs to discrete subcellular locations.
authors: Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
authors: Scott R
authors: SR
authors: DeBoer
authors: YiMei
authors: Y
authors: You
authors: Anita
authors: A
authors: Szodorai
authors: Agnieszka
authors: A
authors: Kaminska
authors: Gustavo
authors: G
authors: Pigino
authors: Evelyn
authors: E
authors: Nwabuisi
authors: Bin
authors: B
authors: Wang
authors: Tatiana
authors: T
authors: Estrada-Hernandez
authors: Stefan
authors: S
authors: Kins
authors: Scott T
authors: ST
authors: Brady
authors: Gerardo
authors: G
authors: Morfini
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology; D019281:Dimerization; D020035:Holoenzymes / Q000032:analysis / Q000737:chemistry / Q000276:immunology; D007425:Intracellular Membranes / Q000737:chemistry; D016547:Kinesins / Q000032:analysis / Q000737:chemistry* / Q000276:immunology; D051379:Mice; D008861:Microsomes / Q000737:chemistry; D021122:Protein Subunits / Q000032:analysis / Q000737:chemistry / Q000276:immunology
chemical_list: D000906:Antibodies; D020035:Holoenzymes; C000715691:Klc2 protein, mouse; C000715695:Kns2 protein, mouse; D021122:Protein Subunits; D016547:Kinesins