title: Role of the tumor suppressor RASSF1A in Mst1-mediated apoptosis.
abstract: Mammalian sterile 20-like kinase 1 (Mst1) is activated by both caspase-mediated cleavage and phosphorylation in response to apoptotic stimuli, including Fas ligation. Here, we examined the possible role of the tumor suppressor RASSF1A in Mst1 activation and Mst1-mediated apoptosis induced by death receptor signaling. Immunoprecipitation and immunofluorescence analyses revealed that Mst1 was associated with RASSF1A in cultured mammalian cells, with both proteins colocalizing to microtubules throughout the cell cycle. Whereas purified recombinant RASSF1A inhibited the kinase activity of purified recombinant Mst1 in vitro, overexpression of RASSF1A increased the kinase activity of Mst1 in intact cells, suggesting that regulation of Mst1 by RASSF1A in vivo involves more than the simple association of the two proteins. Both the activation of Mst1 and the incidence of apoptosis induced by Fas ligation were markedly reduced in cells depleted of RASSF1A by RNA interference and were increased by restoration of RASSF1A expression in RASSF1A-deficient cells. Moreover, the stimulatory effect of RASSF1A overexpression on Fas-induced apoptosis was inhibited by depletion of Mst1. These findings indicate that RASSF1A facilitates Mst1 activation and thereby promotes apoptosis induced by death receptor signaling.
authors.affiliation: Department of Biological Sciences, Biomedical Research Center, Korea Advanced Institute of Science and Technology, Daejeon, South Korea.
authors.forename: Hyun Jung
authors.initials: HJ
authors.lastname: Oh
authors.forename: Kyung-Kwon
authors.initials: KK
authors.lastname: Lee
authors.forename: Su Jung
authors.initials: SJ
authors.lastname: Song
authors.forename: Mi Sun
authors.initials: MS
authors.lastname: Jin
authors.forename: Min Sup
authors.initials: MS
authors.lastname: Song
authors.forename: Joo Hyun
authors.initials: JH
authors.lastname: Lee
authors.forename: Chang Rak
authors.initials: CR
authors.lastname: Im
authors.forename: Jie-Oh
authors.initials: JO
authors.lastname: Lee
authors.forename: Shin
authors.initials: S
authors.lastname: Yonehara
authors.forename: Dae-Sik
authors.initials: DS
authors.lastname: Lim
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D000090742:Serine-Threonine Kinase 3; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D019014:fas Receptor / Q000378:metabolism; D000099317:Hippo Kinases
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D017346:Protein Serine-Threonine Kinases; D034741:RNA, Small Interfering; D000090742:Serine-Threonine Kinase 3; D025521:Tumor Suppressor Proteins; D019014:fas Receptor; C411762:RASSF1 protein, human; C095566:STK4 protein, human; D000099317:Hippo Kinases; C097835:STK3 protein, human