title: Leukocyte-specific protein 1 interacts with DC-SIGN and mediates transport of HIV to the proteasome in dendritic cells.
abstract: Dendritic cells (DCs) capture and internalize human immunodeficiency virus (HIV)-1 through C-type lectins, including DC-SIGN. These cells mediate efficient infection of T cells by concentrating the delivery of virus through the infectious synapse, a process dependent on the cytoplasmic domain of DC-SIGN. Here, we identify a cellular protein that binds specifically to the cytoplasmic region of DC-SIGN and directs internalized virus to the proteasome. This cellular protein, leukocyte-specific protein 1 (LSP1), was defined biochemically by immunoprecipitation and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. LSP1 is an F-actin binding protein involved in leukocyte motility and found on the cytoplasmic surface of the plasma membrane. LSP1 interacted specifically with DC-SIGN and other C-type lectins, but not the inactive mutant DC-SIGNDelta35, which lacks a cytoplasmic domain and shows altered virus transport in DCs. LSP1 diverts HIV-1 to the proteasome. Down-regulation of LSP1 with specific small interfering RNAs in human DCs enhanced HIV-1 transfer to T cells, and bone marrow DCs from lsp1(-/-) mice also showed an increase in transfer of HIV-1(BaL) to a human T cell line. Proteasome inhibitors increased retention of viral proteins in lsp1(+/+) DCs, and substantial colocalization of virus to the proteasome was observed in wild-type compared with LSP1-deficient cells. Collectively, these data suggest that LSP1 protein facilitates virus transport into the proteasome after its interaction with DC-SIGN through its interaction with cytoskeletal proteins.
authors.affiliation: Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Alvin L
authors.initials: AL
authors.lastname: Smith
authors.forename: Lakshmanan
authors.initials: L
authors.lastname: Ganesh
authors.forename: Kwanyee
authors.initials: K
authors.lastname: Leung
authors.forename: Jenny
authors.initials: J
authors.lastname: Jongstra-Bilen
authors.forename: Jan
authors.initials: J
authors.lastname: Jongstra
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Nabel
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D003713:Dendritic Cells / Q000821:virology*; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D037181:Lectins, C-Type / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D034622:RNA Interference; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000235:genetics; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013601:T-Lymphocytes / Q000821:virology; D000099215:DC-Specific ICAM-3 Grabbing Nonintegrin
chemical_list: D015815:Cell Adhesion Molecules; D037181:Lectins, C-Type; D008840:Microfilament Proteins; D046988:Proteasome Endopeptidase Complex; D011956:Receptors, Cell Surface; D012697:Serine Endopeptidases; D000099215:DC-Specific ICAM-3 Grabbing Nonintegrin; C489183:LSP1 protein, human; C436412:Prss28 protein, mouse