c-Mos proteolysis is independent of the CA(2+) rise induced by 6-DMAP in Xenopus oocytes.
In Xenopus oocytes, metaphase II arrest is due to a cytostatic factor (CSF) that involves c-Mos, maintaining a high MPF (cdk1/cyclin B) activity in the cell. At fertilization, a rise in intracellular calcium triggers the proteolysis of both cyclin B and c-Mos. The kinase inhibitor 6-dimethylaminopurine (6-DMAP) is also able to release matured Xenopus oocytes from metaphase II block. This is characterized by c-Mos proteolysis without degradation of cyclin B. We hypothesized that 6-DMAP induced an increase in intracellular calcium. Using the calcium-sensitive fluorescent dye Fura-2, we observed a systematic increase in intracellular calcium following 6-DMAP application. In matured oocytes previously microinjected with the calcium chelator BAPTA, no calcium changes occurred after 6-DMAP addition; however, c-Mos was still proteolysed. In oocytes at the GVBD stage, c-Mos proteolysis occurred in response to 6-DMAP but not to calcium ionophore treatment. We suggest that c-Mos proteolysis is rather controlled by a phosphorylation-dependent process.
Bodart
J F
JF
Laboratoire de Biologie du Développement, Régulation Ionique et Moléculaire du Cycle Cellulairw, UPRES EA 1033, Université de Lille 1, SN3, F-59655 Villeneuve d'Ascq cedex, France.
Rodeau
J L
JL
Vilain
J P
JP
Flament
S
S
D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D016257:Fura-2 / Q000493:pharmacokinetics; D008677:Metaphase / Q000187:drug effects / Q000502:physiology; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D017231:Proto-Oncogene Proteins c-mos / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis / Q000196:embryology / Q000378:metabolism*
D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; C001020:N(6),N(6)-dimethyladenine; D017231:Proto-Oncogene Proteins c-mos; D010447:Peptide Hydrolases; D000225:Adenine; D002118:Calcium; D016257:Fura-2