3c22
Crystal structure of the carbohydrate recognition domain of human Langerin
Structural highlights
Disease[CLC4K_HUMAN] Defects in CD207 are the cause of Birbeck granule deficiency (BIRGD) [MIM:613393]. It is a condition characterized by the absence of Birbeck granules in epidermal Langerhans cells. Despite the lack of Birbeck granules Langerhans cells are present in normal numbers and have normal morphologic characteristics and antigen-presenting capacity.[1] [2] Function[CLC4K_HUMAN] Calcium-dependent lectin displaying mannose-binding specificity. Induces the formation of Birbeck granules (BGs); is a potent regulator of membrane superimposition and zippering. Binds to sulfated as well as mannosylated glycans, keratan sulfate (KS) and beta-glucans. Facilitates uptake of antigens and is involved in the routing and/or processing of antigen for presentation to T cells. Major receptor on primary Langerhans cells for Candida species, Saccharomyces species, and Malassezia furfur. Protects against human immunodeficiency virus-1 (HIV-1) infection. Binds to high-mannose structures present on the envelope glycoprotein which is followed by subsequent targeting of the virus to the Birbeck granules leading to its rapid degradation.[3] [4] [5] [6] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedDendritic cells, a sentinel immunity cell lineage, include different cell subsets that express various C-type lectins. For example, epidermal Langerhans cells express langerin and some dermal dendritic cells express DC-SIGN. Langerin is a crucial component of Birbeck granules, the Langerhans cell hallmark organelle and may have a preventive role towards HIV, by its internalization into Birbeck granules. Since langerin carbohydrate recognition domain (CRD) is crucial for HIV interaction and Birbeck granule formation, we produced the CRD of human langerin and solved its structure at 1.5 ? resolution. On this basis gp120 high-mannose oligosaccharides binding have been evaluated by molecular modeling. Hydrodynamic studies reveal a very elongated shape of recombinant langerin extracellular domain (ECD). A molecular model of the langerin ECD, integrating the CRD structure, has been generated and validated by comparison with hydrodynamics parameters. In parallel, Langerhans cells were isolated from human skin. From their analysis by electron microscopy and the langerin ECD model, an ultrastructural organization is proposed for Birbeck granules. To delineate the role of the different langerin domains in Birbeck granule formation, we generated truncated and mutated langerin constructs. After transfection into a fibroblastic cell line, we highlighted, in accordance with our model, the role of the CRD in the membrane zipping occurring in BG formation as well as some contribution of the cytoplasmic domain. Finally, we have shown that langerin ECD triggering with a specific mAb promotes global rearrangements of LC morphology. Our results open the way to the definition of a new membrane deformation mechanism. Structural Studies of Langerin and Birbeck Granules: a Macromolecular Organization Model.,Th Paut M, Valladeau J, Nurisso A, Kahn R, Arnou B, Viv S C, Sealand S, Ebel C, Monnier C, Dezutter-Dambuyant C, Imberty A, Fieschi F Biochemistry. 2009 Jan 28. PMID:19175323[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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