title: Transient translocation of the B cell receptor and Src homology 2 domain-containing inositol phosphatase to lipid rafts: evidence toward a role in calcium regulation.
abstract: Membrane microdomains (lipid rafts) are enriched in selected signaling molecules and may compartmentalize receptor-mediated signals. Here, we report that in primary human B lymphocytes and in Ramos B cells B cell receptor (BCR) stimulation induces rapid and transient redistribution of a subset of engaged BCRs to lipid rafts and phosphorylation of raft-associated tyrosine kinase substrates. Cholesterol sequestration disrupted the lipid rafts, preventing BCR redistribution, but did not inhibit tyrosine kinase activation or phosphorylation of mitogen-activated protein kinase/extracellular regulated kinase. However, raft disruption enhanced the release of calcium from intracellular stores, suggesting that rafts may sequester early signaling events that down-regulate calcium flux. Consistent with this, BCR stimulation induced rapid and transient translocation of the Src homology 2 domain-containing inositol phosphatase, SHIP, into lipid rafts.
authors.affiliation: Departments of Biochemistry and Molecular Biology and Physiology and Biophysics, University of Calgary, Calgary, Alberta, Canada.
authors.forename: R J
authors.initials: RJ
authors.lastname: Petrie
authors.forename: P P
authors.initials: PP
authors.lastname: Schnetkamp
authors.forename: K D
authors.initials: KD
authors.lastname: Patel
authors.forename: M
authors.initials: M
authors.lastname: Awasthi-Kalia
authors.forename: J P
authors.initials: JP
authors.lastname: Deans
mesh_terms: D001402:B-Lymphocytes / Q000201:enzymology / Q000378:metabolism*; D001692:Biological Transport / Q000276:immunology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000276:immunology*; D002648:Child; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D008563:Membrane Lipids / Q000302:isolation & purification / Q000378:metabolism*; D014066:Palatine Tonsil; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism* / Q000502:physiology; D013379:Substrate Specificity / Q000276:immunology; D014407:Tumor Cells, Cultured; D018909:src Homology Domains / Q000276:immunology*
chemical_list: D008563:Membrane Lipids; D011947:Receptors, Antigen, B-Cell; D011505:Protein-Tyrosine Kinases; D010744:Phosphoric Monoester Hydrolases; C021822:myo-inositol-1 (or 4)-monophosphatase; C098706:INPPL1 protein, human; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D002118:Calcium