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.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arrestins / genetics
  • Arrestins / physiology*
  • Base Sequence
  • Clathrin / metabolism
  • Clathrin / physiology*
  • DNA Primers
  • Endocytosis*
  • GTP-Binding Proteins / metabolism
  • Mice
  • Mice, Knockout
  • Microscopy, Fluorescence
  • RNA, Small Interfering / metabolism
  • Receptors, Cell Surface / metabolism
  • Receptors, Chemokine / metabolism
  • Receptors, Chemokine / physiology*
  • Viral Proteins / metabolism
  • Viral Proteins / physiology*
  • beta-Arrestins


  • Arrestins
  • Clathrin
  • DNA Primers
  • RNA, Small Interfering
  • Receptors, Cell Surface
  • Receptors, Chemokine
  • US28 receptor, Cytomegalovirus
  • Viral Proteins
  • beta-Arrestins
  • GTP-Binding Proteins