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Am J Physiol. 1999 Nov;277(5 Pt 1):C859-69.

Receptor phosphorylation does not mediate cross talk between muscarinic M(3) and bradykinin B(2) receptors.

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  • 1Department of Cell Physiology, University of Leicester, Leicester, United Kingdom.


This study examined cross talk between phospholipase C-coupled muscarinic M(3) and bradykinin B(2) receptors coexpressed in Chinese hamster ovary (CHO) cells. Agonists of either receptor enhanced phosphoinositide signaling (which rapidly desensitized) and caused protein kinase C (PKC)-independent, homologous receptor phosphorylation. Muscarinic M(3) but not bradykinin B(2) receptors were also phosphorylated after phorbol ester activation of PKC. Consistent with this, muscarinic M(3) receptors were phosphorylated in a PKC-dependent fashion after bradykinin B(2) receptor activation, but muscarinic M(3) receptor activation did not influence bradykinin B(2) receptor phosphorylation. Despite heterologous phosphorylation of muscarinic M(3) receptors, phosphoinositide and Ca(2+) signaling were unaffected. In contrast, marked heterologous desensitization of bradykinin-mediated responses occurred despite no receptor phosphorylation. This desensitization was associated with a sustained component of muscarinic receptor-mediated signaling, whereas bradykinin's inability to influence muscarinic receptor-mediated responses was associated with rapid and full desensitization of bradykinin responses. Thus the mechanism of functional cross talk most likely involves depletion of a shared signaling component. These data demonstrate that receptor phosphorylation is not a prerequisite for heterologous desensitization and that such desensitization is not obligatory after heterologous receptor phosphorylation.

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