BFRP

Monogenic diseases

2008/5.19/31

Cell Signal. 2008 Jul;20(7):1275-1283. Epub 2008 Mar 4. Links

betagamma subunits of G(i/o) suppress EGF-induced ERK5 phosphorylation, whereas ERK1/2 phosphorylation is enhanced.

Obara Y, Okano Y, Ono S, Yamauchi A, Hoshino T, Kurose H, Nakahata N.

Department of Cellular Signaling, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba 6-3, Aramaki, Aoba-ku, Sendai 980-8578, Japan; 21st Century COE program “CRESCENDO”, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba 6-3, Aramaki, Aoba-ku, Sendai 980-8578, Japan.

Extracellular signal-regulated kinases (ERKs) play important physiological roles in proliferation, differentiation and gene expression. ERK5 is twice the size of ERK1/2, the amino-terminal half contains the kinase domain that shares the homology with ERK1/2 and TEY activation motif, whereas the carboxy-terminal half is unique. In this study, we examined the cross-talk mechanism between G-protein-coupled receptors (GPCRs) and receptor tyrosine kinases, focusing on ERK1/2 and 5. The pretreatment of rat pheochromocytoma cells (PC12) with pertussis toxin (PTX) specifically enhanced epidermal growth factor (EGF)-induced ERK5 phosphorylation. In addition, lysophosphatidic acid (LPA) attenuated the EGF-induced ERK5 phosphorylation in LPA(1) receptor- and G(i/o)-dependent manners. On the other hand, LPA alone activated ERK1/2 via Gbetagamma subunits and Ras and potentiated EGF-induced ERK1/2 phosphorylation at late time points. These results suggest G(i/o) negatively regulates ERK5, while it positively regulates ERK1/2. LPA did not affect cAMP levels after EGF treatment, and the reagents promoting cAMP production such as forskolin and cholera toxin also attenuated the EGF-induced ERK5 phosphorylation, indicating that the inhibitory effect of LPA on ERK5 inhibition via G(i/o) is not due to inhibition of adenylyl cyclase by Galpha(i/o). However, the inhibitory effect of LPA on ERK5 was abolished in PC12 cells stably overexpressing C-terminus of GPCR kinase2 (GRK2), and overexpression of Gbeta(1) and gamma(2) subunits also suppressed ERK5 phosphorylation by EGF. In response to LPA, Gbetagamma subunits interacted with EGF receptor in a time-dependent manner. These results strongly suggest that LPA negatively regulates the EGF-induced ERK5 phosphorylation through Gbetagamma subunits.

PMID: 18407464 [PubMed - as supplied by publisher]

: PLoS ONE. 2008 Apr 2;3(4):e1903. Links

GPCR genes are preferentially retained after whole genome duplication.

Semyonov J, Park JI, Chang CL, Hsu SY.

Division of Reproductive Biology, Department of Obstetrics and Gynecology, Stanford University School of Medicine, Stanford, California, United States of America.

One of the most interesting questions in biology is whether certain pathways have been favored during evolution, and if so, what properties could cause such a preference. Due to the lack of experimental evidence, whether select gene families have been preferentially retained over time after duplication in metazoan organisms remains unclear. Here, by syntenic mapping of nonchemosensory G protein-coupled receptor genes (nGPCRs which represent half the receptome for transmembrane signaling) in the vertebrate genomes, we found that, as opposed to the 8-15% retention rate for whole genome duplication (WGD)-derived gene duplicates in the entire genome of pufferfish, greater than 27.8% of WGD-derived nGPCRs which interact with a nonpeptide ligand were retained after WGD in pufferfish Tetraodon nigroviridis. In addition, we show that concurrent duplication of cognate ligand genes by WGD could impose selection of nGPCRs that interact with a polypeptide ligand. Against less than 2.25% probability for parallel retention of a pair of WGD-derived ligands and a pair of cognate receptor duplicates, we found a more than 8.9% retention of WGD-derived ligand-nGPCR pairs--threefold greater than one would surmise. These results demonstrate that gene retention is not uniform after WGD in vertebrates, and suggest a Darwinian selection of GPCR-mediated intercellular communication in metazoan organisms.

PMID: 18382678 [PubMed - in process]

Biochim Biophys Acta. 2007 Apr;1768(4):994-1005. Epub 2006 Oct 5. Links

Impact of GPCRs in clinical medicine: monogenic diseases, genetic variants and drug targets.

Insel PA, Tang CM, Hahntow I, Michel MC.

University of California San diego, Department of Pharmacology, La Jolla, CA 92093-0636, USA. pinsel@ucsd.edu

By virtue of their large number, widespread distribution and important roles in cell physiology and biochemistry, G-protein-coupled receptors (GPCR) play multiple important roles in clinical medicine. Here, we focus on 3 areas that subsume much of the recent work in this aspect of GPCR biology: (1) monogenic diseases of GPCR; (2) genetic variants of GPCR; and (3) clinically useful pharmacological agonists and antagonists of GPCR. Diseases involving mutations of GPCR are rare, occurring in <1/1000 people, but disorders in which antibodies are directed against GPCR are more common. Genetic variants, especially single nucleotide polymorphisms (SNPs), show substantial heterogeneity in frequency among different GPCRs but have not been evaluated for some GPCR. Many therapeutic agonists and antagonists target GPCR and show inter-subject variability in terms of efficacy and toxicity. For most of those agents, it remains an open question whether genetic variation in primary sequence of the GPCR is an important contributor to such inter-subject variability, although this is an active area of investigation.

PMID: 17081496 [PubMed - indexed for MEDLINE]

Expert Opin Ther Targets. 2005 Dec;9(6):1247-65. Links

Genetic variation in G-protein-coupled receptors--consequences for G-protein-coupled receptors as drug targets.

Tang CM, Insel PA.

Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093-0636, USA.

G-protein-coupled receptors (GPCRs), including 'orphan' GPCRs whose natural ligands are unknown, comprise the largest membrane receptor superfamily and are the most commonly used therapeutic targets. GPCR genetic loci harbour numerous variants, such as DNA insertions or deletions and single nucleotide polymorphisms that alter GPCR expression and function, thereby contributing to inter-individual differences in disease susceptibility/progression and drug responses. In this article, the authors review examples of GPCR genetic variants that influence transcription, translation, receptor folding and expression on cell surface (by affecting receptor trafficking, dimerisation, desensitisation/downregulation), or perturb receptor function (by altering ligand binding, G-protein coupling and receptor constitutive activity). In spite of such effects, assessment for genetic variants is not currently applied to the drug development and approval process or in the clinical use of GPCR drugs. Further insights will, the authors believe, alter drug discovery/development, therapeutics and likely provide new GPCR drug targets.

PMID: 16300474 [PubMed - indexed for MEDLINE]

Biochemistry. 2007 Mar 20;46(11):3476-81. Epub 2007 Feb 14. Links

J Cell Physiol. 2007 Sep 4; [Epub ahead of print] Links

Mitogenic signaling pathways induced by G protein-coupled receptors.

Rozengurt E.

Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, CURE: Digestive Diseases Research Center and Molecular Biology Institute, University of California at Los Angeles, Los Angeles, California.

G protein-coupled receptor (GPCR) agonists, including neurotransmitters, hormones, chemokines, and bioactive lipids, act as potent cellular growth factors and have been implicated in a variety of normal and abnormal processes, including development, inflammation, and malignant transformation. Typically, the binding of an agonistic ligand to its cognate GPCR triggers the activation of multiple signal transduction pathways that act in a synergistic and combinatorial fashion to relay the mitogenic signal to the nucleus and promote cell proliferation. A rapid increase in the activity of phospholipases C, D, and A2 leading to the synthesis of lipid-derived second messengers, Ca(2+) fluxes and subsequent activation of protein phosphorylation cascades, including PKC/PKD, Raf/MEK/ERK, and Akt/mTOR/p70S6K is an important early response to mitogenic GPCR agonists. The EGF receptor (EGFR) tyrosine kinase has emerged as a transducer in the signaling by GPCRs, a process termed transactivation. GPCR signal transduction also induces striking morphological changes and rapid tyrosine phosphorylation of multiple cellular proteins, including the non-receptor tyrosine kinases Src, focal adhesion kinase (FAK), and the adaptor proteins CAS and paxillin. The pathways stimulated by GPCRs are extensively interconnected by synergistic and antagonistic crosstalks that play a critical role in signal transmission, integration, and dissemination. The purpose of this article is to review recent advances in defining the pathways that play a role in transducing mitogenic responses induced by GPCR agonists. J. Cell. Physiol. (c) 2007 Wiley-Liss, Inc.

PMID: 17786953 [PubMed - as supplied by publisher]

Cell Cycle. 2007 Jun;6(16):2058-70. Epub 2007 Jun 8. Links

Galpha13 regulation of proto-Dbl signaling.

Vanni C, Mancini P, Ottaviano C, Ognibene M, Parodi A, Merello E, Russo C, Varesio L, Zheng Y, Torrisi MR, Eva A.

Laboratorio di Biologia Molecolare, Istituto G. Gaslini, Genova, Italy.

Rho family GTPases play important roles in the regulation of intracellular signals induced by activated heterotrimeric G proteins of the alpha(12/13) family. The alpha(12/13) subunits activate Rho GTPases through direct binding to a group of Rho guanine nucleotide exchange factors (GEFs) characterized by the presence of a G protein signaling-like (RGL) domain. The Rho GEF proto-Dbl, that does not contain a RGL domain, was also found to link Galpha(12/13) signals to Rho. We have explored the effects of activated Galpha(13) and Galpha(13)-associated G protein-coupled receptor (GPCR) agonists on proto-Dbl regulation. We show that activated Galpha(13), but not Galpha(12) or Galpha(q), induces translocation of proto-Dbl to the cell membrane with consequent enlargement of cell body and membrane ruffling. These effects were evident also when Galpha(13)-associated GPCR agonists were used on cells expressing proto-Dbl and were accompanied by the activation of Cdc42 and RhoA GTPases and further downstream effector JNK and p38 kinases. Moreover, we show that both activated Galpha(13) and GPCR agonists stimulate proto-Dbl interaction with ezrin to promote ezrin translocation to the plasma membrane. These results suggest a mechanism by which proto-Dbl and its effector pathways are regulated by Galpha(13)-mediated signals through association with ezrin.

PMID: 17721084 [PubMed - in process]