Role of HRB in clathrin-dependent endocytosis

J Biol Chem. 2008 Dec 5;283(49):34365-73. doi: 10.1074/jbc.M804587200. Epub 2008 Sep 25.

Abstract

Human immunodeficiency virus Rev-binding protein (HRB), also called human Rev-interacting protein (hRIP) or Rev/Rex activation domain binding (RAB) is a partner of the tyrosine kinase substrate EPS15, and it has been recovered in the AP-2 interactome. EPS15 and AP-2 are involved in endocytosis, but the function of HRB in this process is still unknown. Here we identified HRB as a partner of the vesicular SNARE tetanus neurotoxin-insensitive vesicle-associated membrane protein (TI-VAMP, also called VAMP7) in yeast two-hybrid screens and using biochemical assays. In HeLa cells, HRB localized both in the nucleus and in the cytoplasm. In the cytoplasm, HRB colocalized with clathrin-, AP-2-, EPS15-, and transferrin receptor-containing vesicles. We did not see significant colocalization between HRB and TI-VAMP in HeLa cells, and we saw partial colocalization with green fluorescent protein-TI-VAMP in stably expressing Madin-Darby canine kidney cells. Nevertheless using a pHLuorin-tagged TI-VAMP construct, we found that HRB and TI-VAMP colocalize close to the plasma membrane after 5 min of anti-green fluorescent protein antibody uptake. These results suggest that TI-VAMP and HRB may interact only during the early stages of endocytosis. Furthermore uptake experiments followed by fluorescence-activated cell sorting showed that the endocytosis of fluorescent transferrin and pHLuorin-TI-VAMP is strongly reduced in HRB knockdown cells. Altogether these results suggest that HRB is involved in clathrin-dependent endocytosis and recruits TI-VAMP in this process.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Clathrin / chemistry
  • Clathrin / physiology*
  • Cloning, Molecular
  • Dogs
  • Endocytosis*
  • Green Fluorescent Proteins / metabolism
  • HeLa Cells
  • Humans
  • Microscopy, Fluorescence
  • Models, Biological
  • Nuclear Pore Complex Proteins / chemistry
  • Nuclear Pore Complex Proteins / physiology*
  • Protein Binding
  • Protein Structure, Tertiary
  • RNA-Binding Proteins / chemistry
  • RNA-Binding Proteins / physiology*
  • Two-Hybrid System Techniques

Substances

  • AGFG1 protein, human
  • Clathrin
  • Nuclear Pore Complex Proteins
  • RNA-Binding Proteins
  • Green Fluorescent Proteins