Chapter 5 The β-adrenoceptors
1993; Elsevier BV; Linguagem: Inglês
10.1016/s0167-7306(08)60358-0
ISSN1875-7901
AutoresMartin J. Lohse, Ruth H. Strasser, Ernst Helmreich,
Tópico(s)Neuropeptides and Animal Physiology
ResumoSignal transmission from β-adrenoceptors to stimulatory G-protein and adenylyl cyclase and signal transmission in the course of visual excitation in retinal rod outer segment membranes are the best-studied examples of G-protein-coupled receptor actions. This chapter discusses important aspects of β-adrenoceptor function, structure, and regulation, including desensitization mechanisms, both under physiological and pathophysiological conditions and pharmacological and clinical aspects. There are two models that explain the way β-receptors activate GTP-binding proteins. One model visualizes the role of the receptor as the catalyst of the exchange of guanosine diphosphate (GDP) bound to the α-subunit of the heterotrimeric αβγ-G-protein complex by guanosine triphosphate (GTP). The model implies that once GTP is bound and the active species of G-proteins has been formed, the receptor is no longer required. The other model incorporates subunit dissociation as an essential feature of G-protein activation. It assumes that GDP–GTP exchange requires the formation of a receptor-G-protein complex. There are at least three β-receptor subtypes—β1, β2, and β3—in mammalian cells that all activate stimulatory G-protein and adenylyl cyclase.
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