title: The formation and stability of DC-SIGN microdomains require its extracellular moiety.
abstract: Dendritic cell-specific intercellular adhesion molecule (ICAM)-3-grabbing non-integrin (DC-SIGN) is a Ca(2+) -dependent transmembrane lectin that binds a large variety of pathogens and facilitates their uptake for subsequent antigen presentation. This receptor is present in cell surface microdomains, but factors involved in microdomain formation and their exceptional stability are not clear. To determine which domain/motif of DC-SIGN facilitates its presence in microdomains, we studied mutations at key locations including truncation of the cytoplasmic tail, and ectodomain mutations that resulted in the removal of the N-linked glycosylation site, the tandem repeats and the carbohydrate recognition domain (CRD), as well as modification of the calcium sites in the CRD required for carbohydrate binding. Confocal imaging and fluorescence recovery after photobleaching measurements showed that the cytoplasmic domain and the N-linked glycosylation site do not affect the ability of DC-SIGN to form stable microdomains. However, truncation of the CRD results in complete loss of visible microdomains and subsequent lateral diffusion of the mutants. Apart from cell adhesions, membrane domains are thought to be localized primarily via the cytoskeleton. By contrast, we propose that interactions between the CRD of DC-SIGN and the extracellular matrix and/or cis interactions with transmembrane scaffolding protein(s) play an essential role in organizing these microdomains.
authors.affiliation: Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Ping
authors.initials: P
authors.lastname: Liu
authors.forename: Xiang
authors.initials: X
authors.lastname: Wang
authors.forename: Michelle S
authors.initials: MS
authors.lastname: Itano
authors.forename: Aaron K
authors.initials: AK
authors.lastname: Neumann
authors.forename: Ken
authors.initials: K
authors.lastname: Jacobson
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Thompson
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D002241:Carbohydrates / Q000737:chemistry; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D037181:Lectins, C-Type / Q000737:chemistry*; D051379:Mice; D008954:Models, Biological; D009154:Mutation; D041681:NIH 3T3 Cells; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000737:chemistry*; D015398:Signal Transduction; D000099215:DC-Specific ICAM-3 Grabbing Nonintegrin
chemical_list: D015703:Antigens, CD; D002118:Calcium; D002241:Carbohydrates; D015815:Cell Adhesion Molecules; D037181:Lectins, C-Type; D011956:Receptors, Cell Surface; D000099215:DC-Specific ICAM-3 Grabbing Nonintegrin; C483616:ICAM3 protein, human; C573564:ICAM3 protein, mouse