INOSITOL PHOSPHOLIPID-METABOLISM IN XENOPUS OOCYTES MEDIATED BY ENDOGENOUS G(O) AND G(I) PROTEINS

To characterize G-proteins which mediate the signal transduction from ligand stimulated receptor to phospholipase C (PLC), we injected antisense DNAs complementary to Xenopus G(0) alpha or G(i-1)alpha to suppress these endogenous G-proteins, together with the mRNAs encoding metabotropic glutamate receptor 1 (mGluR1), 5 (mGluR5) or with M1 type muscarinic receptor into oocytes. Receptor-stimulated chloride current responses were reduced by the suppression of Xenopus G(0) alpha regardless of the types of receptors. However, injection of G(i-1) antisense DNA resulted in the reduction of M1-stimulated responses but not mGluR-stimulated responses. These results suggested that all these receptors could use G(0) alpha, and M1 receptors, but not mGluRs, could also use G(i-1) proteins, to activate PLC in Xenopus oocytes.