Defective Kinesin Heavy Chain Behavior in Mouse Kinesin Light Chain Mutants

Abstract

Conventional kinesin, kinesin-I, is a heterotetramer of two kinesin heavy chain (KHC) subunits (KIF5A, KIF5B, or KIF5C) and two kinesin light chain (KLC) subunits. While KHC contains the motor activity, the role of KLC remains unknown. It has been suggested that KLC is involved in either modulation of KHC activity or in cargo binding. Previously, we characterized KLC genes in mouse (Rahman, A., D.S. Friedman, and L.S. Goldstein. 1998. J. Biol. Chem. 273:15395–15403). Of the two characterized gene products, KLC1 was predominant in neuronal tissues, whereas KLC2 showed a more ubiquitous pattern of expression. To define the in vivo role of KLC, we generated KLC1 gene-targeted mice. Removal of functional KLC1 resulted in significantly smaller mutant mice that also exhibited pronounced motor disabilities. Biochemical analyses demonstrated that KLC1 mutant mice have a pool of KIF5A not associated with any known KLC subunit. Immunofluorescence studies of sensory and motor neuron cell bodies in KLC1 mutants revealed that KIF5A colocalized aberrantly with the peripheral cis-Golgi marker giantin in mutant cells. Striking changes and aberrant colocalization were also observed in the intracellular distribution of KIF5B and β′-COP, a component of COP1 coatomer. Taken together, these data best support models that suggest that KLC1 is essential for proper KHC activation or targeting.

Association of Kinesin Light Chain with Outer Dense Fibers in a Microtubule-independent Fashion

“…Interestingly, male haploid germ cells do not detectably synthesize KLC1 and KLC2, as determined by reverse transcription-PCR, suggesting that KLC3 probably carries out its function in transport and other motor-based processes and/or that other spermatid KLCs remain to be identified. This is in agreement with the observation that male KLC1 knockout mice are fertile (19). Kinesin-related proteins (KRPs), which do not contain light chains, have also been described in rat testis (21,22), and two KRPs have sequence similarity to the previously described BimC subfamily of KRPs involved in mitosis (23).…”

“…As mentioned, KLCs may also regulate KHC and keep it in an inactive state by preventing the active conformation of KHC (11). This was supported by the recent analysis of KLC1 knockout mice; mutant mice were small and exhibited motor disabilities (19). Also, in these mice, a pool of KHC KIF5A was mislocalized to the peripheral cis-Golgi.…”

Axonal Transport, Amyloid Precursor Protein, Kinesin-1, and the Processing Apparatus: Revisited

“…TR domain sequences are homologous in both KLC1 and KLC2 and highly conserved at the amino acid level (Tsai et al, 2000). Nonetheless, KLC1 and KLC2 appear to be associated with different subsets of membrane-bound organelles (Leopold et al, 1992;Elluru et al, 1995;Stenoien and Brady, 1997;Rahman et al, 1999). Hydrophobic stretches in TRs would tend to drive relatively nonspecific binding with other proteins containing suitable hydrophobic patches.…”

“…Immunoprecipitations were performed as described by Kamal et al (2000) and Rahman et al (1999). Mouse brain was homogenized in 3 ml of NP-40 homogenization buffer (NB; 1% NP-40, 150 mM NaCl, 50 mM Tris, pH 8.0).…”

Transcriptome analysis of distinct mouse strains reveals kinesin light chain-1 splicing as an amyloid-β accumulation modifier

“…KLC1, with expression that is enriched in neuronal tissue (31), is required for cargo binding and the regulation of motility. Among myosin and kinesin family members, splicing is a common strategy to facilitate motor cargo selection, and the many splice variants of KLC1 in the C-terminal region likely allow it to select different cargos (32).…”