The Molecules of HIV

Note: this site last updated in 2006


An article from "The Molecules of HIV" (c) Dan Stowell

CXCR4 (aka "fusin") and CCR5 are both chemokine receptors. That is, they are proteins normally embedded in the membrane of a cell, and responds to the presence of chemokines outside the cell to trigger some kind of response within the cell.

HIV-1 is able to use either CXCR4 or CCR5 as a co-receptor (CD4 being the main receptor) to facilitate binding and entry into T cells. There are other possible co-receptors, but these are most commonly used.

CXCR4 was the first HIV coreceptor to be discovered, and it's one of the most important ones.

In HIV-positive individuals, the level of expression of CXCR4 is downregulated (i.e. less is produced) in T cells, and studies have found that CXCR4 expression remains low even after HAART treatment.

More information:

  • Naming: These receptors are so called because they are receptors of CXC chemokines. CXC chemokines (such as CXCR4) are distinct from CC chemokines (such as CCR5) in that they have one amino acid imbetween the first two cysteine residues, instead of them being adjacent.
  • HIV strains which use CXCR4 are called "X4";HIV strains which use CCR5 are called "R5"

Written by
Dan Stowell

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