title: The rap GTPases regulate B cell morphology, immune-synapse formation, and signaling by particulate B cell receptor ligands.
abstract: B lymphocytes spread and extend membrane processes when searching for antigens and form immune synapses upon contacting cells that display antigens on their surface. Although these dynamic morphological changes facilitate B cell activation, the signaling pathways underlying these processes are not fully understood. We found that activation of the Rap GTPases was essential for these changes in B cell morphology. Rap activation was important for B cell receptor (BCR)- and lymphocyte-function-associated antigen-1 (LFA-1)-induced spreading, for BCR-induced immune-synapse formation, and for particulate BCR ligands to induce localized F-actin assembly and membrane-process extension. Rap activation and F-actin assembly were also required for optimal BCR signaling in response to particulate antigens but not soluble antigens. Thus by controlling B cell morphology and cytoskeletal organization, Rap might play a key role in the activation of B cells by particulate and cell-associated antigens.
authors.affiliation: Department of Microbiology and Immunology, I3 and CELL Research Groups, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
authors.forename: Kevin B L
authors.initials: KB
authors.lastname: Lin
authors.forename: Spencer A
authors.initials: SA
authors.lastname: Freeman
authors.forename: Saba
authors.initials: S
authors.lastname: Zabetian
authors.forename: Hayley
authors.initials: H
authors.lastname: Brugger
authors.forename: Michele
authors.initials: M
authors.lastname: Weber
authors.forename: Victor
authors.initials: V
authors.lastname: Lei
authors.forename: May
authors.initials: M
authors.lastname: Dang-Lawson
authors.forename: Kathy W K
authors.initials: KW
authors.lastname: Tse
authors.forename: Rene
authors.initials: R
authors.lastname: Santamaria
authors.forename: Facundo D
authors.initials: FD
authors.lastname: Batista
authors.forename: Michael R
authors.initials: MR
authors.lastname: Gold
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D017951:Antigen Presentation / Q000276:immunology; D001402:B-Lymphocytes / Q000201:enzymology* / Q000276:immunology / Q000648:ultrastructure*; D002460:Cell Line; D004789:Enzyme Activation / Q000502:physiology; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology*; D051379:Mice; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D011947:Receptors, Antigen, B-Cell / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*; D020668:rap GTP-Binding Proteins / Q000276:immunology / Q000378:metabolism*
chemical_list: D000199:Actins; D011947:Receptors, Antigen, B-Cell; D020668:rap GTP-Binding Proteins