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Figure 4 | Respiratory Research

Figure 4

From: Signaling and regulation of G protein-coupled receptors in airway smooth muscle

Figure 4

G protein-coupled receptor regulation in airway smooth muscle. Regulation of G protein-coupled receptor signaling at the receptor locus is effected by numerous mechanisms that establish the number and responsiveness of receptors at the cell surface. These mechanisms include new receptor synthesis, as well as modes of desensitization and resensitization that unfold after a receptor is activated by agonist. Receptor uncoupling occurs as a result of G protein-coupled receptor kinase (GRK) -mediated phosphorylation of agonist-occupied receptor, which promotes arrestin binding to phosphorylated receptor and steric inhibition of GPCR-G protein interaction. Arrestin binding to receptor also initiates internalization of receptor into clathrin-coated pits, after which receptors can traffick to lysosomes for degradation (downregulation) or be dephosphorylated and recycled back to the plasma membrane (resensitization). In addition, activation of intracellular kinases such as protein kinase A (PKA) or protein kinase C (PKC) can also phosphorylate GPCRs and promote a loss of GPCR-G protein coupling. See text for details.

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