Hsp90 is required for c-Mos activation and biphasic MAP kinase activation in Xenopus oocytes.
During Xenopus oocyte maturation, the Mos protein kinase is synthesized and activates the MAP kinase cascade. In this report, we demonstrate that the synthesis and activation of Mos are two separable processes. We find that Hsp90 function is required for activation and phosphorylation of Mos and full activation of the MAP kinase cascade. Once Mos is activated, Hsp90 function is no longer required. We show that Mos interacts with both Hsp90 and Hsp70, and that there is an inverse relationship between association of Mos with these two chaperones. We propose that Mos protein kinase is activated by a novel mechanism involving sequential association with Hsp70 and Hsp90 as well as phosphorylation. We also present evidence for a two-phase activation of MAP kinase in Xenopus oocytes.
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CNRS-CRBM, 1919 Route de Mende, 34293 Montpellier, Cedex 05, France.
Mandart
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D000818:Animals; D001483:Base Sequence; D004789:Enzyme Activation; D005260:Female; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D066298:In Vitro Techniques; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D020319:Oligodeoxyribonucleotides, Antisense / Q000235:genetics; D009865:Oocytes / Q000254:growth & development / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis; D017231:Proto-Oncogene Proteins c-mos / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014981:Xenopus
D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D020319:Oligodeoxyribonucleotides, Antisense; D011994:Recombinant Proteins; D017231:Proto-Oncogene Proteins c-mos; D020928:Mitogen-Activated Protein Kinases