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. 2003 Apr;4(4):243-53.
doi: 10.1034/j.1600-0854.2003.00079.x.

Endocytosis of the viral chemokine receptor US28 does not require beta-arrestins but is dependent on the clathrin-mediated pathway

Alberto Fraile-Ramos  1 , Trudy A Kohout, Maria Waldhoer, Mark Marsh
Affiliations
Free article

Endocytosis of the viral chemokine receptor US28 does not require beta-arrestins but is dependent on the clathrin-mediated pathway

Alberto Fraile-Ramos et al. Traffic. 2003 Apr.
Free article

Abstract

Arrestins bind phosphorylated G-protein coupled-receptors (GPCR) and inhibit agonist-induced signal transduction by uncoupling the receptors from their cognate G-proteins. beta-arrestins also act as adaptors that target GPCR to endocytic clathrin-coated vesicles. Unlike cellular GPCRs, the human cytomegalovirus GPCRs and chemokine receptor, US28, shows constitutive signal transduction activity and undergoes constitutive endocytosis. To determine the role of beta-arrestins in US28 trafficking, we used embryonic fibroblasts derived from beta-arrestin knockout mice. In these cells, the internalization of transfected beta2-adrenergic receptor and of the cellular chemokine receptor CCR5 was impaired. By contrast, US28 distribution was unaffected, and US28-mediated RANTES internalization was similar in normal and knockout cell lines. To investigate whether a clathrin-mediated pathway is involved in US28 endocytosis, we developed small interfering RNA against the micro2-adaptin subunit of the AP-2 adaptor complex. In cells transfected with micro2 small interfering RNA transferrin endocytosis was severely inhibited. Antibody-feeding experiments and biochemical analysis showed that US28 internalization was also inhibited. Together, these data indicate that US28 endocytosis occurs via a clathrin-mediated mechanism but is independent of beta-arrestins.

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