These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Chimeric G alpha s/G alpha i2 proteins define domains on G alpha s that interact with tubulin for beta-adrenergic activation of adenylyl cyclase.
    Author: Popova JS, Johnson GL, Rasenick MM.
    Journal: J Biol Chem; 1994 Aug 26; 269(34):21748-54. PubMed ID: 8063818.
    Abstract:
    Previous studies have demonstrated that dimeric tubulin, associated with synaptic membrane, is capable of activating the G-proteins Gs and G alpha i1 via transfer of GTP. To clarify the mechanism of intracellular interaction between tubulin and G alpha s as it refers to adenylyl cyclase activation, wild type and chimeric G alpha s/G alpha i2 proteins were transiently overexpressed in COS 1 cells. Effects of tubulin dimers with guanosine 5'-(beta, gamma-imido)triphosphate (Gpp(NH)p) bound (tubulin-Gpp(NH)p) or Gpp NH)p with/without isoproterenol on adenylyl cyclase were assessed in cells made permeable with saponin. In naive and wild type G alpha s-overexpressing COS 1 cells, the beta-adrenergic agonist isoproterenol potentiated significantly the stimulatory effects of Gpp(NH)p and, to an even greater extent, tubulin-Gpp(NH)p on adenylyl cyclase. In COS 1 cells expressing the chimera G alpha i(54)/s (G alpha i2 1-54, G alpha s 62-394 amino acids), tubulin-Gp-p (NH)p was more potent than Gpp(NH)p in the presence of isoproterenol, but the maximal activity was equal. In chimera G alpha s/i(38) (G alpha s 1-356, G alpha i2 357-392) tubulin-Gp-p(NH)p or Gpp(NH)p stimulated adenylyl cyclase activity 11-14 times above the control whether or not beta-adrenergic receptor was activated, suggesting that G alpha chimera and the beta-adrenergic receptor are uncoupled. The chimera G alpha i/s(Bam) (G alpha i2 1-212, G alpha s 213-292) was nearly identical to native COS 1 cells, but isoproterenol potentiated Gpp(NH)p but not the tubulin-Gpp(NH)p response. The construct G alpha i(Bam)/s/i(38) (G alpha i2 1-212, G alpha s 213-356, G alpha i2 357-392) was weakly responsive to Gpp(NH)p or tubulin-Gpp(NH)p and unresponsive to isoproterenol. In photoaffinity labeling studies with tubulin-[32P]azidoanilido-GTP (tubulin-[32P]AAGTP), isoproterenol increased the amount of tubulin associated with membranes and the transfer of [32P]AAGTP from tubulin to G alpha i(54)/s, G alpha s, and G alpha i/s(Bam), but not to G alpha i(Bam)/s/i(38) and very slightly to G alpha s/i(38). These results suggest that regions between the 54th and 212th amino acids of G alpha s are important for guanine nucleotide transfer from tubulin, while the 1st to 54th amino acids of G alpha s are required for the ability of tubulin to activate adenylyl cyclase. We speculate that the active G alpha s conformation provoked by nucleotide transfer from tubulin is stabilized by G alpha s-tubulin interaction leading to extended stimulation of adenylyl cyclase.
    [Abstract] [Full Text] [Related] [New Search]