Published ahead of print on January 24, 2008, doi:10.1165/rcmb.2007-0118OC Am. J. Respir. Cell Mol. Biol., Volume 38, Number 6, June 2008, 738-743 A more recent version of this article appeared on June 1, 2008
Submitted on April 4, 2007 Tyrosine Sulfation Is Prevalent in Human Chemokine Receptors Important in Lung DiseaseJustin Liu1,1 Section of Neurobiology, Physiology, and Behavior, University of California, Davis, CA, USA, 2 Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine, University of California, Davis, CA, USA, 3 Pittsburgh Supercomputing Center, Pittsburgh, PA, USA * To whom correspondence should be addressed. E-mail: rosenqui{at}yahoo.com.
Post-translational sulfation of tyrosines affects the affinity and binding of at least some chemokine receptors to their ligand(s) and has been hypothesized to be a feature in all chemokine receptors. This binding initiates downstream signaling cascades. By this mechanism, tyrosine sulfation can influence the cells involved in acute and chronic events of cellular immunity. These events include leukocyte trafficking and airway inflammation important in asthma and chronic obstructive pulmonary disease (COPD). We are using computational methods to convert the poorly defined hypothesis of more widespread sulfation of chemokine receptors to more specific assessments of how closely the sequence environment of each tyrosine residue resembles the sequence environment of tyrosine residues proven to be sulfated. Thus, we provide specific and readily tested hypotheses about the tyrosine residues in all of the chemokine receptors. Tyrosine sulfation was predicted with high scores in the N-terminus domain of 13 out of 18 human chemokine receptor proteins using a Position-Specific Scoring Matrix (PSSM), which was determined to be 94.2% accurate based on Receiver Operating Characteristic (ROC) analysis. The remaining chemokine receptors have sites exhibiting features of tyrosine sulfation. These putative sites demonstrate clustering in a manner consistent with known tyrosine sulfation sites and conservation both within the chemokine receptor family and across mammalian species. Human chemokine receptors important in asthma and COPD such as CXCR1, CXCR2, CXCR3, CXCR4, CCR1, CCR2, CCR3, CCR4, CCR5 and CCR8, contain at least one known or predicted tyrosine sulfation site.
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