KIF2beta , a new kinesin superfamily protein in non-neuronal cells, is associated with lysosomes and may be implicated in their centrifugal translocation

Abstract

Lysosomes concentrate juxtanuclearly in the region around the microtubule-organizing center by interaction with microtubules. Different experimental and physiological conditions can induce these organelles to move to the cell periphery by a mechanism implying a plus-end-directed microtubule-motor protein (a kinesin-like motor). The responsible kinesin-superfamily protein, however, is unknown. We have identified a new mouse isoform of the kinesin superfamily, KIF2β, an alternatively spliced isoform of the known, neuronal kinesin, KIF2. Developmental expression pattern and cell-type analysis in vivo and in vitro reveal that KIF2β is abundant at early developmental stages of the hippocampus but is then downregulated in differentiated neuronal cells, and it is mainly or uniquely expressed in non-neuronal cells while KIF2 remains exclusively neuronal. Electron microscopy of mouse fibroblasts and immunofluorescence of KIF2β-transiently-transfected fibroblasts show KIF2 and KIF2β primarily associated with lysosomes, and this association can be disrupted by detergent treatment. In KIF2β-overexpressing cells, lysosomes (labeled with anti-lysosome-associated membrane protein-1) become abnormally large and peripherally located at some distance from their usual perinuclear positions. Overexpression of KIF2 or KIF2β does not change the size or distribution of early, late and recycling endosomes nor does overexpression of different kinesin superfamily proteins result in changes in lysosome size or positioning. These results implicate KIF2β as a motor responsible for the peripheral translocation of lysosomes.

A novel family of katanin-like 2 protein isoforms (KATNAL2), interacting with nucleotide-binding proteins Nubp1 and Nubp2, are key regulators of different MT-based processes in mammalian cells

“…For in vitro co-selection assays to study KATNAL2 interactions, GST fusions of KATNAL2-S1 and -L1 were generated from pGEX-4T-1 constructs and used together with His-tagged fusions of Nubp1 and Nubp2 in pRSET B . Mammalian expression of KATNAL2 isoforms, tagged with different epitopes was driven from plasmids pEGFP-C2 (Clontech), pmCherry-C3 (Ellenberg group, EMBL), pFLAG-CVM-1 (Sigma) and pSVmyc1.0 [41] (summarized in Table S1). A yeast two-hybrid screen was conducted by Hybrigenics (France), using full-length mouse Nubp1 cDNA as bait (hgx1836v1) against a mouse embryo brain RP1 cDNA prey library in pB27 (LexA, C-terminal fusion) and analyzing 58.04 million interactions.…”

Powering membrane traffic in endocytosis and recycling

“…In mammalian cells, a rigor mutant of kinesin-1 blocks plus-end-directed lysosome movement 93 , and targeted disruption of the gene that encodes kinesin-1 impairs lysosome dispersion 94 . Last, an intriguing finding is that KIF2β, a splice variant of KIF2 that is found in non-neuronal cells and a member of the kinesin-13 family, supposedly drives plus-end-directed transport of lysosomes 95 . This is odd because other members of the kinesin-13 family are non-motile and possess micro tubule-depolymerizing activity 96 .…”

All kinesin superfamily protein, KIF, genes in mouse and human

“…The cargo of KIF2A includes ␤ gc , a ␤-subunit of the insulin-like growth factor-1 receptor (95). A splice variant of KIF2A has been reported (96). A Xenopus homolog of KIF2A, XKIF2, is reported to destabilize microtubules in vitro (104).…”