Identification and Pharmacological Characterization of Domains Involved in Binding of CGRP Receptor Antagonists to the Calcitonin-like Receptor
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- 作者：Christopher A. Salvatore ; John J. Mallee ; Ian M. Bell ; C. Blair Zartman ; Theresa M. Williams ; Kenneth S. Koblan ; and Stefanie A. Kane
- 刊名：Biochemistry
- 出版年：2006
- 出版时间：February 14, 2006
- 年：2006
- 卷：45
- 期：6
- 页码：1881 - 1887
- 全文大小：222K
- 年卷期：v.45,no.6(February 14, 2006)
- ISSN：1520-4995
文摘
The calcitonin-like receptor (CLR) and the calcitonin receptor (CTR) interact with receptoractivity-modifying protein 1 (RAMP1) at the cell surface to form heterodimeric receptor complexes. CLRand CTR are members of the class II (family B) G-protein-coupled receptors (GPCR) and bind calcitoningene-related peptide (CGRP) with similar affinities when coexpressed with RAMP1. The observationthat various nonpeptide CGRP receptor antagonists display a higher affinity for the CLR/RAMP1 complexthan for CTR/RAMP1 provided an opportunity to investigate the molecular determinants of the differentialreceptor affinities of these antagonists. A chimeric receptor approach was utilized to identify key domainswithin CLR responsible for conferring high-affinity antagonist binding. Initial chimera experimentsimplicated distinct regions within CLR as responsible for the affinities of structurally diverse CGRP receptorantagonists. Dissection of these key regions implicated amino acids 37-63 located in the amino terminusof CLR as responsible for the high-affinity interaction of one structural class, while transmembrane domain(TM) 7 was responsible for the interaction of a second class of antagonist. A unique binding interactionin the amino terminus of CLR is consistent with the observation that these compounds also interact withthe extracellular region of RAMP1 and could suggest the formation of a binding pocket between the twoproteins. Conversely, a compound which interacted with TM7 did not display a similar RAMP1 dependence,suggesting an allosteric mechanism of antagonism. Collectively, these data provide insight into twoalternative mechanisms of antagonism for this unique heterodimeric receptor complex.