title: Defining the conformation of human mincle that interacts with mycobacterial trehalose dimycolate.
abstract: Trehalose dimycolate, an unusual glycolipid in the outer membrane of Mycobacterium tuberculosis, stimulates macrophages by binding to the macrophage receptor mincle. This stimulation plays an important role both in infection by mycobacteria and in the use of derivatives of mycobacteria as adjuvants to enhance the immune response. The mechanism of trehalose dimycolate binding to the C-type carbohydrate-recognition domain in human mincle has been investigated using a series of synthetic analogs of trehalose dimycolate and site-directed mutagenesis of the human protein. The results support a mechanism of binding acylated trehalose derivatives to human mincle that is very similar to the mechanism of binding to bovine mincle, in which one glucose residue in the trehalose headgroup of the glycolipid is ligated to the principle Ca(2+)-binding site in the carbohydrate-recognition domain, with specificity for the disaccharide resulting from interactions with the second glucose residue. Acyl chains attached to the 6-OH groups of trehalose enhance affinity, with the affinity dependent on the length of the acyl chains and the presence of a hydrophobic groove adjacent to the sugar-binding sites. The results indicate that the available crystal structure of the carbohydrate-recognition domain of human mincle is unlikely to be in a fully active conformation. Instead, the ligand-binding conformation probably resembles closely the structure observed for bovine mincle in complex with trehalose. These studies provide a basis for targeting human mincle as a means of inhibiting interactions with mycobacteria and as an approach to harnessing the ability of mincle to stimulate the immune response.
authors.affiliation: Department of Life Sciences, Imperial College, Sir Ernst Chain Building, London SW7 2AZ, UK.
authors.forename: Sabine A F
authors.initials: SA
authors.lastname: Jégouzo
authors.affiliation: Department of Life Sciences, Imperial College, Sir Ernst Chain Building, London SW7 2AZ, UK.
authors.forename: Edward C
authors.initials: EC
authors.lastname: Harding
authors.affiliation: Department of Life Sciences, Imperial College, Sir Ernst Chain Building, London SW7 2AZ, UK.
authors.forename: Oliver
authors.initials: O
authors.lastname: Acton
authors.affiliation: Department of Life Sciences, Imperial College, Sir Ernst Chain Building, London SW7 2AZ, UK.
authors.forename: Maximus J
authors.initials: MJ
authors.lastname: Rex
authors.affiliation: Department of Life Sciences, Imperial College, Sir Ernst Chain Building, London SW7 2AZ, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Fadden
authors.affiliation: Department of Life Sciences, Imperial College, Sir Ernst Chain Building, London SW7 2AZ, UK.
authors.forename: Maureen E
authors.initials: ME
authors.lastname: Taylor
authors.affiliation: Department of Life Sciences, Imperial College, Sir Ernst Chain Building, London SW7 2AZ, UK k.drickamer@imperial.ac.uk.
authors.forename: Kurt
authors.initials: K
authors.lastname: Drickamer
mesh_terms: D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry; D002417:Cattle; D003311:Cord Factors / Q000138:chemical synthesis / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D037181:Lectins, C-Type / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D009169:Mycobacterium tuberculosis / Q000737:chemistry*; D011487:Protein Conformation; D011971:Receptors, Immunologic / Q000737:chemistry* / Q000378:metabolism
chemical_list: C482593:CLEC4D protein, human; D003311:Cord Factors; D037181:Lectins, C-Type; D011971:Receptors, Immunologic; D002118:Calcium
keywords: C-type lectin; Mycobacterium tuberculosis; glycan-binding receptor; glycolipid; mincle