Guanosine 5'-O-(3-thiotrisphosphate) potentiates both thrombin- and platelet-derived growth factor-induced inositol phosphate release in permeabilized vascular smooth muscle cells. Signaling mechanisms distinguished by sensitivity to pertussis toxin and phorbol esters

C. L. Huang, H. E. Ives

Research output: Contribution to journalArticle

40 Scopus citations


We compared the mechanisms by which thrombin and platelet-derived growth factor (PDGF) activate phospholipase C in cultured vascular smooth muscle cells. Thrombin caused a transient (<5 min) increase in inositol trisphosphate (IP3) while PDGF caused a sustained (>10 min) increase. Both pertussis toxin and phorbol 12-myristate 13-acetate (PMA) inhibited the thrombin-induced increase in IP3 but neither agent affected the PDGF-induced increase in IP3. To examine the role of GTP binding (G) proteins in the activation of phospholipase C by these two hormones, GTP analogues were introduced into saponin-permeabilized cells. In the absence of hormones, guanosine 5'-O-(3-thiotrisphosphate) (GTPγS) caused a progressive increase in IP3 release which was inhibited 55% by PMA (200 ng/ml). In the presence of thrombin, GTPγS caused synergistic increase in IP3 release. The synergism between GTPγS and thrombin was virtually eliminated by 10 min prior exposure to PMA (200 ng/ml). When PDGF was the hormonal agonist, GTPγS also caused synergistic increase in IP3 release and guanosine 5'-O-(2-thiodiphosphate) blunted PDGF-induced IP3 release. However, in contrast to thrombin, the synergism between GTPγS and PDGF was unaffected by PMA. Thus, thrombin and PDGF activate phospholipase C by signal transduction systems which differ in kinetic properties and in sensitivity to PMA and pertussis toxin. Despite these differences, both systems appear to involve GTP binding proteins at some step.

Original languageEnglish (US)
Pages (from-to)4391-4397
Number of pages7
JournalJournal of Biological Chemistry
Issue number8
StatePublished - Jan 1 1989


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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