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  • Title: Involvement of G alpha q/11 in m3-muscarinic receptor stimulation of phosphatidylinositol 4,5 bisphosphate-specific phospholipase C in rat parotid gland membranes.
    Author: Sawaki K, Hiramatsu Y, Baum BJ, Ambudkar IS.
    Journal: Arch Biochem Biophys; 1993 Sep; 305(2):546-50. PubMed ID: 8396894.
    Abstract:
    Carbachol stimulation of phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis by rat parotid gland membranes is dependent on the presence of GTP gamma S and is a result of m3-muscarinic receptor regulation of G-protein coupled, PIP2-specific phospholipase C (PLC). The PLC activity (> 80%) was solubilized with 1% Na-cholate but the solubilized enzyme was not stimulated by GTP gamma S and carbachol. Immunoblotting of rat parotid membranes with polyclonal antiserum, which recognizes alpha-subunits of the Gq/11 family, indicated the presence of two immunoreactive proteins of approximate molecular weights 41 and 42 kDa. Incubation of membranes with the common G alpha q/11 antiserum attenuated the stimulation of PIP2 hydrolysis, induced by GTP gamma S alone and by carbachol, in the presence of GTP gamma S. The antiserum had no effect on PIP2 hydrolysis in unstimulated membranes or in the cholate extract, where it is uncoupled from the G-protein. Antiserum against G alpha i, which is also coupled to the m3-muscarinic receptor in this tissue, had no effect on either basal or stimulated PIP2 hydrolysis. These results demonstrate that in rat parotid gland, activation of PIP2-specific PLC by m3-muscarinic receptor stimulation is mediated via alpha-subunits of the Gq/11 family of G-proteins.
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