Coupling of M2 Muscarinic Receptors to Membrane Ion Channels via Phosphoinositide 3-Kinase γ and Atypical Protein Kinase C*
- From the Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104 and the ‡Kimmel Cancer Institute, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
Abstract
We report a novel signaling pathway linking M2 muscarinic receptors to metabotropic ion channels. Stimulation of heterologously expressed M2 receptors, but not other Gi/Go-associated receptors (M4 or α2c), activates a calcium- and voltage-independent chloride current in Xenopus oocytes. We show that the stimulatory pathway linking M2 receptors to these chloride channels consists of Gβγ stimulation of phosphoinositide 3-kinase γ (PI-3Kγ), formation of phosphatidylinositol 3,4,5-trisphosphate (PIP3), and activation of atypical protein kinase C (PKC). The chloride current is activated in the absence of M2 receptor stimulation by the injection of PIP3, and PIP3 current activation is blocked by a pseudosubstrate inhibitory peptide of atypical PKC but not other PKCs. Moreover, the current is activated by injection of recombinant PKCζ at concentrations as low as 1 nm. M2 receptor-current coupling was disrupted by inhibiton of PI-3K and by injection of βγ binding peptides, but it was not affected by expression of dominant negative p85 cRNA. We also show that this pathway mediates M2 receptor coupling to metabotropic nonselective cation channels in mammalian smooth muscle cells, thus demonstrating the broad relevance of this signaling cascade in neurotransmitter signaling.
Footnotes
-
↵* This work was supported by National Institutes of Health Grants HL45239 and HL41084 (to M. I. K.) and a grant from the American Heart Association (to Y.-X. W.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵§ To whom correspondence should be addressed: Dept. of Animal Biology, University of Pennsylvania, 3800 Spruce St., Philadelphia, PA 19104-6046. Tel.: 215-898-2839; Fax: 215-573-6810; E-mail:mik{at}vet.upenn.edu.
- Abbreviations:
- PI-3K
-
phosphoinositide 3-kinase
- PIP3
-
phosphatidylinositol 3,4,5-trisphosphate
- PKC
-
protein kinase C
- aPKC
-
atypical PKC
- cPKC
-
conventional PKC
- mACH
-
methacholine
- GF109203X
-
bisindolylmaleimide I
-
- Received December 23, 1998.
- Revision received February 9, 1999.
- The American Society for Biochemistry and Molecular Biology, Inc.
