Abstract
The parathyroid hormone receptor (PTHR) is a class B G protein-coupled receptor (GPCR) that mediates the endocrine and paracrine effects of parathyroid hormone and related peptides through the activation of phospholipase Cβ-, adenylyl cyclase-, mitogen-activated protein kinase-, and β-arrestin-initiated signaling pathways. It is currently not clear how specificity among these downstream signaling pathways is achieved. A possible mechanism involves adaptor proteins that affect receptor/effector coupling. In a proteomic screen with the PTHR C terminus, we identified vav2, a guanine nucleotide exchange factor (GEF) for Rho GTPases, as a PTHR-interacting protein. The core domains of vav2 bound to the intracellular domains of the PTHR independent of receptor activation. In addition, vav2 specifically interacted with activated Gαq but not with Gαs subunits, and it competed with PTHR for coupling to Gαq. Consistent with its specific interaction with Gαq, vav2 impaired Gq-mediated inositol phosphate generation but not Gs-mediated cAMP generation. This inhibition of Gq signaling was specific for PTHR signaling, compared with other Gq-coupled GPCRs. Moreover, the benefit for PTHR-mediated inositol phosphate generation in the absence of vav2 required the ezrin binding domain of Na+/H+-exchanger regulatory factor 1. Our results show that a RhoA GEF can specifically interact with a GPCR and modulate its G protein signaling specificity.
Footnotes
↵ The online version of this article (available at http://molpharm.aspetjournals.org) contains supplemental material.
This work was supported by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 487 “Regulatorische Membranproteine,” Bayerische Forschungsstiftung (scholarship to A.E.N.), and the European Research Council [Advanced Grant “Towards the Quantal Nature of Receptor/cAMP Signals”].
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
ABBREVIATIONS:
- GPCR
- G protein-coupled receptor
- α1B-AR
- α1B-adrenergic receptor
- CT
- C-terminal domain
- GEF
- guanine nucleotide exchange factor
- M-AChR
- muscarinic acetylcholine receptor
- NHERF
- Na+/H+-exchanger regulatory factor
- PDZ
- postsynaptic density 95/Drosophila discs large/zona occludens
- PLC
- phospholipase C
- PTH
- parathyroid hormone
- PTHR
- parathyroid hormone receptor
- DH
- Dbl-homology
- PH
- pleckstrin-homology
- PAGE
- polyacrylamide gel electrophoresis
- DMEM
- Dulbecco's modified Eagle's medium
- NP40
- Nonidet P-40
- dnNHERF
- dominant-negative Na+/H+-exchanger regulatory factor 1(1–326)
- siRNA
- small interfering RNA
- HA
- hemagglutinin
- MERM
- merlin/ezrin/radixin/moesin
- IP
- inositol phosphate
- MBP
- maltose-binding protein.
- Received March 19, 2012.
- Accepted May 3, 2012.
- Copyright © 2012 The American Society for Pharmacology and Experimental Therapeutics
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