摘要：

YM-254890, which was isolated from the culture broth of sp., inhibits ADP-induced platelet aggregation and has antithrombotic and thrombolytic effects. YM-254890 blocks Gα-coupled ADP receptor P2Y1-mediated Camobilization. Here we report that YM-254890 is a selective Gαinhibitor. YM-254890 blocked Camobilization mediated by several Gα-coupled receptors but not by Gα- or Gα-coupled receptor, indicating that phospholipase Cβ activation and subsequent signaling molecules are not the target of YM-254890. YM-254890 completely prevented the serum response factor (SRF)-mediated gene transcription induced by GαR183C, which is constitutively active in a receptor-dependent manner because of its reduced of GTP hydrolysis. Conversely, YM-254890 had only a modest effect on the SRF-mediated gene transcription by GαQ209L, which is GTPase-deficient (activated) Gα. These suggested that the acting point of YM-254890 is receptor-Gαinteraction or the subsequent guanine nucleotide exchange step. The fact that YM-254890 (i) inhibited the SRF-mediated gene transcription by Gα, which interacts with Gα-coupled receptor and possesses the effector function of Gα, and (ii) had no effect on the value of high affinity [H]2MeSADP binding to P2Y1, which reflects the agonist-receptor-Gα ternary complex, suggested that receptor-Gαinteraction is not the target of YM-254890. On the other hand, specific [S]GTPγS binding to Gαstimulated by the M1 muscarinic acetylcholine receptor and P2Y1 were inhibited by YM-254890. These data indicate that YM-254890 blocks the exchange of GDP for GTP in Gαactivation. This novel Gα-selective inhibitor is a promising and powerful tool for studying Gαprotein activation, Gα-coupled receptor signaling, and Gα-mediated biological events.

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