Postgraduate Researchers in Science Medicine Conference 2005: Abstracts
Function and regulation of Metastasis associated Kinase-V(MAK-V) in mammalian cell cycle
Shoba Sekar and David Stott
MAK-V/Hunk, a serine threonine kinase expressed at elevated levels in mammary gland tumours exhibits homology to the PAR-1 family of protein kinases. The subcellular localisation of MAK-V by indirect immunofluorescence indicates co-localisation with gamma-tubulin to the centrosome. Depolymerisation of microtubules by nocodazole treatment reduced the intensity of MAK-V staining at the centrosome while taxol treatment had the complementary effect. Disruption of actin filaments by cytochalasin treatment diminished MAK-V staining slightly. Overexpression of dynamitin, subunit of dynein, resulted in the accumulation of MAK-V in the cytoplasm suggesting the mode of transport of MAK-V to the centrosome. MAK-V abundance is cell cycle regulated with peak levels in S and G2 phase. MAK-V protein has a rapid turnover rate with a half-life of 180 minutes. Destruction of MAK-V is mediated by proteasome suggesting ubiquitination. Treatment of mammalian cells with proteasome inhibitors prevented MAK-V degradation. MAK-V degradation is regulated by two-destruction box motif (RxxL) in the N-terminus region of the protein. Complete stabilisation of MAK-V requires the point mutation of conserved arginine in both the boxes. Overexpression of stabilised MAK-V stimulated centrosome splitting, suggesting a role in centrosome separation.
Shoba Sekar, Biological Sciences, Gibbet Hill Road, University of Warwick, Coventry CV4 7AL
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