2 FORMS OF G(O)-TYPE G-PROTEINS - IDENTIFICATION AND DISTRIBUTION IN VARIOUS RAT-TISSUES AND CLONED CELLS

A G(o) type G protein distinct from the major species of G(o) was recently isolated from bovine brain and designated G(o)*. The cDNAs encoding two forms of mammalian G(o)alpha were also isolated and designated G(o)A-alpha and G(o)B-alpha. To recognize two forms of G(o) type G proteins, we raised antibodies in rabbits against two peptides with sequences found only in the respective proteins of murine G(o)A-alpha (SNTYEDAAAYIQTQF) and G(o)B-alpha (TEAVAHIQGQYESK). Purified anti-G(o)A-alpha antibodies reacted with the major species of G(o)-alpha purified from bovine and rat brain, whereas anti-G(o)B-alpha antibodies reacted only with rat G(o)*alpha, but not with the major species of G(o)alpha or bovine G(o)*alpha. These results indicate that the major species of G(o)alpha is encoded by G(o)A-alpha cDNA and G(o)*alpha is encoded by G(o)B-alpha cDNA. Using these antibodies, the distribution of G(o)A and G(o)B was studied in various rat tissues and cloned cells. Both G(o)A and G(o)B were present in many tissues, but their distribution in peripheral tissues was distinct. G(o)A-alpha seemed to associate mainly with neural tissues. On the other hand, relatively high concentrations of G(o)B-alpha were present in the brain, pituitary gland, adipose tissue, lung, and testis. The concentrations of both G(o)A and G(o)B in the brain increased during ontogenic development, but the increase in G(o)B was observed at a later age. Both G(o)A and G(o)B were found in such cloned cells as PC12, NG 108-15, C6, GA-1, G8, and 3T3-L1 cells. Treatment of PC12 cells with nerve growth factor caused the extension of neuron-like processes and the increase in the level of G(o)A, but not in the level of G(o)B.