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

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

  • Traffic. 2003 Apr;4(4):243-53. doi: 10.1034/j.1600-0854.2003.00079.x.
Alberto Fraile-Ramos 1 Trudy A Kohout Maria Waldhoer Mark Marsh
Affiliations

Affiliation

  • 1 Cell Biology Unit, MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, UK.
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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