TUBULIN STIMULATES ADENYLYL-CYCLASE ACTIVITY IN RAT STRIATAL MEMBRANES VIA TRANSFER OF GUANINE-NUCLEOTIDE TO CS PROTEIN

Previous studies of rat cerebral cortex and rat C6 glioma cells have d emonstrated that dimeric tubulin is capable of activating the G protei ns Gs and Gil via transfer of guanine nucleotide from tubulin to Gs al pha and Gil alpha. To provide further information regarding cytoskelet al modulation of adenylyl cyclase, the present study examined effects of tubulin on the activation of the enzyme in rat striatal membranes. Tubulin, prepared from rat brain by polymerization with the hydrolysis -resistant GTP analog 5'-guanylylimidodiphosphate (GppNHp) caused sign ificant activation of adenylyl cyclase by similar to 130%. Furthermore , tubulin-GppNHp activated SKF 38393-sensitive adenylyl cyclase and po tentiated forskolin-stimulated activity of the enzyme. When tubulin, p olymerized with the hydrolysis-resistant photoaffinity GTP analog [(32 )p]p(3) (4-azidoanilido)-p(1)-5'-GTP ([P-32]AAGTP), was incubated with striatal membranes, AAGTP was transferred from tubulin to Gs alpha as well as Gi alpha with the extents of nucleotide transfers being 7.6 /- 0.8% and 17.8 +/- 1.4% of AAGTP originally bound to tubulin, respec tively. These results indicate that, in rat striatum, the tubulin dime r participates in the stimulatory regulation of adenylyl cyclase by tr ansferring guanine nucleotide to Gs alpha, supporting the hypothesis t hat tubulin contributes to the regulation of neuronal signal transduct ion.