It is becoming clear that receptors that initiate signal transduction by interacting with G-proteins do not function as monomers, but often require accessory proteins for function. Some of these accessory proteins are chaperones, required for correct transport of the receptor to the cell surface, but the function of many accessory proteins remains unknown. We determined the role of an accessory protein for the receptor for calcitonin generelated peptide (CGRP), a potent vasodilator neuropeptide. We have previously shown that this accessory protein, the CGRP-receptor component protein (RCP), is expressed in CGRP responsive tissues and that RCP protein expression correlates with the biological efficacy of CGRP in vivo. However, the function of RCP has remained elusive. In this study stable cell lines were made that express antisense RCP RNA, and CGRP-and adrenomedullin-mediated signal transduction were greatly reduced. However, the loss of RCP did not effect CGRP binding or receptor density, indicating that RCP did not behave as a chaperone but was instead coupling the CGRP receptor to downstream effectors. A candidate CGRP receptor named calcitonin receptor-like receptor (CRLR) has been identified, and in this study RCP co-immunoprecipitated with CRLR indicating that these two proteins interact directly. Since CGRP and adrenomedullin can both signal through CRLR, which has been previously shown to require a chaperone protein for function, we now propose that a functional CGRP or adrenomedullin receptor consists of at least three proteins: the receptor (CRLR), the chaperone protein (RAMP), and RCP that couples the receptor to the cellular signal transduction pathway.G protein-coupled receptors are generally thought to function as monomers that interact with G proteins to initiate signal transduction. However, it has recently been recognized that many G protein-coupled receptors require additional proteins for function. These proteins range from other receptors that form dimers, to heterologous accessory proteins that function primarily as chaperones (1, 2). In this study we report a novel accessory protein that does not act as a chaperone, but instead couples the receptor to the cellular signal transduction pathway. Thus, our concept of a G protein-coupled receptor involves a complex of proteins that are required for receptor function, including correct intracellular sorting, organization in the plasma membrane, and coupling to cellular signal transduction proteins.Calcitonin gene-related peptide (CGRP) 1 is a potent vasoactive neuropeptide, which has been implicated in vasodilation, migraine, and chronic pain (3-6). Despite the clinical implications of CGRP's biological actions, therapeutic strategies targeting CGRP have been hindered by the lack of a functional CGRP receptor. CGRP binding results in increased intracellular cAMP levels (7,8), and a candidate G protein-coupled receptor has been identified called the calcitonin receptor-like receptor (CRLR) (9). However, CRLR was initially non-functional when trans...

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Objective. To examine the effects of intraarticular induction of interleukin-1␤ (IL-1␤) expression in adult mice.Methods. We used somatic mosaic analysis in a novel transgenic mouse with an inducible IL-1␤ transcription unit. Transgene activation was induced by Cre recombinase in the temporomandibular joints (TMJs) of adult transgenic mice (conditional knockin model). The effects of intraarticular IL-1␤ induction were subsequently evaluated at the cellular, histopathologic, and behavioral levels. Osteoarthritis (OA) manifests as a slowly progressing debilitating disease that affects one or more joints of the body. Clinical symptoms include pain, dysfunction, and swelling and enlargement of the joints. The primary pathologic features of OA are fibrillation and loss of articular cartilage, accompanied by remodeling of subchondral bone. OA seems to be a node of convergence for a number of potentially independent pathologic processes that, ultimately, can lead to joint dysfunction and pain (1). Although the role of inflammation in OA has been long debated (2), recent evidence now confirms proinflammatory cytokines as mediators in this disease (3). For example, the catabolism of OA cartilage is thought to involve the action of proinflammatory cytokines such as interleukin-1 (IL-1)

Calcitonin gene-related peptide (CGRP), adrenomedullin (ADM), amylin and calcitonin (CT) are structurally and functionally related neuropeptides. It has recently been shown that the molecular pharmacology of CGRP and ADM is determined by coexpression of one of three receptor activity-modifying proteins (RAMPs) with calcitonin receptor-like receptor (CRLR). Furthermore, RAMP proteins have also been shown to govern the pharmacology of the calcitonin receptor, which in association with RAMP1 or RAMP3, binds amylin with high affinity. In this study, we have cloned the rat RAMP family and characterized the pharmacology of rat CGRP and ADM receptors. Rat RAMP1, RAMP2 and RAMP3 shared 72%, 69% and 85% homology with their respective human homologues. As expected CRLR-RAMP1 coexpression conferred sensitivity to CGRP, whilst association of RAMP2 or RAMP3 with CRLR conferred high affinity ADM binding. Using specific oligonucleotides we have determined the expression of RAMP1, RAMP2 and RAMP3 mRNAs in the rat central nervous system by in situ hybridization. The localization of RAMP mRNAs was heterogeneous. RAMP1 mRNA was predominantly expressed in cortex, caudate putamen and olfactory tubercles; RAMP2 mRNA was most abundant in hypothalamus; and RAMP3 was restrictively expressed in thalamic nuclei. Interestingly, in specific brain areas only a single RAMP mRNA was often detected, suggesting mutual exclusivity in expression. These data allow predictions to be made of where each RAMP protein may heterodimerize with its partner G-protein-coupled receptor(s) at the cellular level and consequently advance current understanding of cellular sites of action of CGRP, ADM, amylin and CT. Furthermore, these localization data suggest that the RAMP family may associate and modify the behaviour of other, as yet unidentified neurotransmitter receptors.

The role of sensory innervation in the regulation of liver physiology and the pathogenesis of cholestatic liver disease are undefined. Biliary proliferation has been shown to be coordinately controlled by parasympathetic and sympathetic innervation of the liver. The aim of our study was to address the role of the sensory neuropeptide calcitonin gene-related peptide (a-CGRP) in the regulation of cholangiocyte proliferation during cholestasis induced by extrahepatic bile duct obstruction (BDL). Our study utilized a knockout (KO) mouse model, which lacks the sensory neuropeptide a-CGRP. Wildtype (WT) and a-CGRP KO mice were subjected to sham surgery or BDL for 3 and 7 days. In addition, immediately after BDL, WT and KO mice were administered the CGRP receptor antagonist (CGRP 8-37 ) for 3 and 7 days by osmotic minipumps. Liver sections and isolated cholangiocytes were evaluated for proliferation markers. Isolated WT BDL (3 days) cholangiocytes were stimulated with a-and b-CGRP and evaluated for proliferation and cAMP-mediated signaling. Lack of a-CGRP inhibits cholangiocyte proliferation induced by BDL at both 3 and 7 days. BDL-induced cholangiocyte proliferation in WT mice was associated with increases of circulating a-CGRP levels. In vitro, a-and b-CGRP stimulated proliferation in purified BDL cholangiocytes, induced elevation of cAMP levels, and stimulated the activation of cAMPdependent protein kinase A and cAMP response element binding protein DNA binding. In conclusion, sensory innervation of the liver and biliary expression of a-CGRP play an important role in the regulation of cholangiocyte proliferation during cholestasis.