Identification of a distinct molecular mass Gα(h) (transglutaminase II) coupled to α(1)-adrenoceptor in mouse heart

초록

Our previous studies on alpha(1)-adrenoceptor signaling suggested that G alpha(h) family is a signal mediator in different species. To elucidate the species-specificity of G alpha(h) family in molecular mass, we used the solubilized membranes from mouse heart and the ternary complex preparations containing alpha(1)-agonist/receptor/G-protein. Binding of [S-35]GTP gamma S and the intensity of the [alpha-P-32]GTP photoaffinity labeled protein resulting from activation of the alpha(1)-adrenoceptor were significantly attenuated by the antagonist, phentolamine. The molecular mass of the specific GTP-binding protein was similar to 72-kDa; homologous with G alpha(h) (transglutaminase II) family. Furthermore, immunological cross-reactivity of ternary complex from mouse heart and purified G alpha(h) from rat, guinea pig, and bovine using anti-G alpha(h7) antibody showed that their molecular masses were distinctly different and similar to 72-kDa G alpha(h) from mouse heart was the lowest molecular mass. Consistent with these observations, in co-immunoprecipitation and co-immunoadsorption of the alpha(1)-adrenoceptor in the ternary complex preparation by anti-G alpha(h7) antibody, the G alpha(h) family protein tightly coupled to alpha(1)-adrenoceptor. These results demonstrate the species-specificity of G alpha(h) family in molecular mass, especially the lowest molecular mass in mouse.

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