Synaptic membrane G proteins are complexed with tubulin in situ.
The G proteins G S and Gi1 appear to be capable of binding to tubulin specifically, and it has been suggested that such binding results in G protein activation via direct transfer of GTP. This study was undertaken to demonstrate that consequences of G protein activation by tubulin, i.e., stimulation or inhibition of adenyl cyclase, were dependent on the G proteins expressed as well as unique aspects of the membrane or cytoskeleton in a given cell type. Membranes from rat C6 glioma cells, which express G s alpha but not G i alpha 1, responded to the addition of tubulin with a stable activation of adenyl cyclase. Conversely, membranes from rat cerebral cortex, which contain both G s and G i 1, responded to exogenous tubulin with a stable inhibition of adenyl cyclase. Unlike C6 membranes, cerebral cortex membranes are richly endowed with tubulin, and antitubulin antibodies immunoprecipitated complexes of tubulin and G i 1 and G s from detergent extracts of these membranes. Nearly 90% of the G s alpha from Triton X-114 extracts coimmunoprecipitated with tubulin, suggesting that these proteins exist as a complex in the synaptic membrane. Such complexes may provide the framework for a G protein-cytoskeleton link that participates in the modulation of cellular signal transduction.
Yan
K
K
Department of Physiology, University of Illinois College of Medicine, Chicago, USA.
Greene
E
E
Belga
F
F
Rasenick
M M
MM
D000067956:Adenylyl Cyclase Inhibitors; D000345:Affinity Labels; D000818:Animals; D001386:Azides; D002540:Cerebral Cortex / Q000378:metabolism; D002645:Chickens; D019204:GTP-Binding Proteins / Q000032:analysis / Q000378:metabolism*; D005910:Glioma; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D051381:Rats; D012756:Sheep; D013570:Synaptic Membranes / Q000737:chemistry* / Q000201:enzymology; D013574:Synaptosomes / Q000737:chemistry / Q000378:metabolism; D014404:Tubulin / Q000378:metabolism* / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000737:chemistry / Q000201:enzymology
D000067956:Adenylyl Cyclase Inhibitors; D000345:Affinity Labels; D001386:Azides; D014404:Tubulin; D006165:Guanylyl Imidodiphosphate; C031907:GTP gamma-4-azidoanilide; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins