A PERIODIC NETWORK OF G-PROTEIN BETA-GAMMA SUBUNIT COEXISTING WITH CYTOKERATIN FILAMENT IN STARFISH OOCYTES

Heterotrimeric G proteins are membrane-bound and carry signals from ac tivated receptors on plasma membranes to cytoplasmic effector enzymes and channels. In starfish oocytes, the beta gamma subunit of G protein mediates 1-methyladenine stimulation of oocyte maturation. In order t o investigate the localization of beta gamma subunits in starfish oocy tes during oocyte maturation, we raised a monoclonal antibody against the beta subunit. By immunofluorescence microscopy using the antibody, immature oocytes show a network of fibers in the cytoplasm. The stain ing of fibers is beaded with a periodicity of 0.7 mu m. The same stain ing pattern is obtained by anti-gamma subunit antibody. In addition, t he fibers are stained by anti-cytokeratin antibody. These results indi cate that the G protein gamma subunit coexists with cytokeratin filame nts in starfish oocytes. Stimulation of oocyte maturation by 1-methyla denine causes the beta gamma subunit to be disassembled. (C) 1995 Acad emic Press,Inc.