title: CD44 Binding to Hyaluronic Acid Is Redox Regulated by a Labile Disulfide Bond in the Hyaluronic Acid Binding Site.
abstract: CD44 is the primary leukocyte cell surface receptor for hyaluronic acid (HA), a component of the extracellular matrix. Enzymatic post translational cleavage of labile disulfide bonds is a mechanism by which proteins are structurally regulated by imparting an allosteric change and altering activity. We have identified one such disulfide bond in CD44 formed by Cys77 and Cys97 that stabilises the HA binding groove. This bond is labile on the surface of leukocytes treated with chemical and enzymatic reducing agents. Analysis of CD44 crystal structures reveal the disulfide bond to be solvent accessible and in the-LH hook configuration characteristic of labile disulfide bonds. Kinetic trapping and binding experiments on CD44-Fc chimeric proteins show the bond is preferentially reduced over the other disulfide bonds in CD44 and reduction inhibits the CD44-HA interaction. Furthermore cells transfected with CD44 no longer adhere to HA coated surfaces after pre-treatment with reducing agents. The implications of CD44 redox regulation are discussed in the context of immune function, disease and therapeutic strategies.
authors.affiliation: The Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom.
authors.forename: Helena
authors.initials: H
authors.lastname: Kellett-Clarke
authors.affiliation: The Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom.
authors.forename: Monika
authors.initials: M
authors.lastname: Stegmann
authors.affiliation: The Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom.
authors.forename: A Neil
authors.initials: AN
authors.lastname: Barclay
authors.affiliation: The Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom.
authors.forename: Clive
authors.initials: C
authors.lastname: Metcalfe
mesh_terms: D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D002448:Cell Adhesion; D002460:Cell Line; D003412:Cricetulus; D018360:Crystallography, X-Ray; D006801:Humans; D018960:Hyaluronan Receptors / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D006820:Hyaluronic Acid / Q000378:metabolism*; D051379:Mice; D010084:Oxidation-Reduction; D011485:Protein Binding; D011961:Receptors, Fc / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D014162:Transfection
chemical_list: C476399:Cd44 protein, mouse; D018960:Hyaluronan Receptors; D011961:Receptors, Fc; D011993:Recombinant Fusion Proteins; D006820:Hyaluronic Acid