The chemokine receptor CCR2 mediates the binding and internalization of monocyte chemoattractant protein-1 along brain microvessels

J Neurosci. 2001 Dec 1;21(23):9214-23. doi: 10.1523/JNEUROSCI.21-23-09214.2001.

Abstract

Previous results from this laboratory revealed the presence of high-affinity saturable binding sites for monocyte chemoattractant protein-1 (MCP-1) along human brain microvessels (Andjelkovic et al., 1999; Andjelkovic and Pachter, 2000), which suggested that CC chemokine receptor 2 (CCR2), the recognized receptor for this chemokine, was expressed by the brain microvascular endothelium. To test the role of CCR2 directly in mediating MCP-1 interactions with the brain microvasculature, we assessed MCP-1 binding activity in murine brain microvessels isolated from wild-type mice and from CCR2 (-/-) mice engineered to lack this receptor. Results demonstrate that MCP-1 binding is greatly attenuated in microvessels prepared from CCR2 (-/-) mice compared with wild-type controls. Moreover, microvessels from wild-type mice exhibited MCP-1-induced downmodulation in MCP-1 binding and a recovery of binding activity that was not dependent on de novo protein synthesis. Furthermore, MCP-1 was shown to be internalized within wild-type microvessels, but not within microvessels obtained from CCR2 (-/-) mice, additionally demonstrating that CCR2 is obligatory for MCP-1 endocytosis. Last, internalization of MCP-1, but not transferrin, was observed to be inhibited by disruption of caveolae. Internalized MCP-1 also colocalized at some sites with caveolin-1, a major protein of caveolae, implying that this chemokine is endocytosed, in part, via nonclathrin-coated vesicles. These results prompt consideration that MCP-1 signals may be relayed across the blood-brain barrier by highly specialized interactions of this chemokine with its cognate receptor, CCR2, along brain microvascular endothelial cells.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Binding, Competitive / physiology
  • Brain / blood supply*
  • Caveolae / drug effects
  • Caveolae / metabolism
  • Caveolin 1
  • Caveolins / metabolism
  • Chemokine CCL2 / metabolism*
  • Chemokines / metabolism
  • Crosses, Genetic
  • Down-Regulation
  • Endocytosis / drug effects
  • Endocytosis / physiology
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / drug effects
  • Endothelium, Vascular / metabolism*
  • Filipin / pharmacology
  • In Vitro Techniques
  • Ligands
  • Mice
  • Mice, Inbred Strains
  • Mice, Knockout
  • Microcirculation / drug effects
  • Microcirculation / metabolism*
  • Protein Binding / physiology
  • Receptors, CCR2
  • Receptors, Chemokine / deficiency
  • Receptors, Chemokine / genetics
  • Receptors, Chemokine / metabolism*
  • Temperature
  • Transferrin / metabolism

Substances

  • CCR2 protein, human
  • Cav1 protein, mouse
  • Caveolin 1
  • Caveolins
  • Ccr2 protein, mouse
  • Chemokine CCL2
  • Chemokines
  • Ligands
  • Receptors, CCR2
  • Receptors, Chemokine
  • Transferrin
  • Filipin