title: Fc alpha receptor cross-linking causes translocation of phosphatidylinositol-dependent protein kinase 1 and protein kinase B alpha to MHC class II peptide-loading-like compartments.
abstract: A20 IIA1.6 B cells cotransfected with FcalphaR and wild-type gamma-chain (wt-ITAM (immunoreceptor tyrosine-based activation motif)) or FcalphaR and gamma-chain, in which the wt-ITAM was substituted with the FcgammaRIIA ITAM (IIA-ITAM), were used to investigate cell signaling events influencing presentation of FcalphaR-targeted exogenous Ag in the context of MHC class II. wt-ITAM cells presented FcalphaR-targeted OVA more efficiently than IIA-ITAM transfectants to OVA-specific T cell hybridomas. Phosphatidylinositol 3-kinase (PI 3-kinase) inhibition abrogated Ag presentation, suggesting that FcalphaR may trigger a PI 3-kinase-dependent signal transduction pathway, and thus phosphatidylinositol-dependent protein kinase (PDK1) and protein kinase B alpha (PKBalpha) activation. Cross-linking FcalphaR on wt-ITAM or IIA-ITAM cells triggered equivalent PI 3-kinase-dependent activation of PKBalpha. Furthermore, FcalphaR cross-linking triggered recruitment of PDK1 and serine-phosphorylated PKBalpha to capped cell surface FcalphaR irrespective of the gamma-chain ITAM. Although FcalphaR endocytosis was accompanied by translocation of PDK1 and phospho-PKBalpha to FcalphaR-containing vesicles in both transfectants, this was decreased in IIA-ITAM cells, and a significant proportion of PDK1 and PKBalpha remained at the plasma membrane. In wt-ITAM cells, PDK1 and serine-phosphorylated PKBalpha translocated to lysosomal-associated membrane glycoprotein 1- and cathepsin B-containing vesicles, consistent with MHC class II peptide-loading compartments (MIIC) described by other groups. Our data indicate that translocation of signal transduction mediators to MIIC-like compartments accompanies efficient presentation of receptor-targeted Ag, and suggest a mechanism connecting signaling to the Ag-processing pathway.
authors: Department of Microbiology, Dartmouth Medical School, Lebanon, NH 03756, USA.
authors: M L
authors: ML
authors: Lang
authors: L
authors: L
authors: Shen
authors: H
authors: H
authors: Gao
authors: W F
authors: WF
authors: Cusack
authors: G A
authors: GA
authors: Lang
authors: W F
authors: WF
authors: Wade
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation / Q000235:genetics; D015703:Antigens, CD / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D001693:Biological Transport, Active / Q000235:genetics / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects / Q000276:immunology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000949:Histocompatibility Antigens Class II / Q000097:blood / Q000378:metabolism*; D006801:Humans; D006825:Hybridomas; D007070:Immunoglobulin A / Q000378:metabolism*; D008213:Lymphocyte Activation / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009000:Monocytes / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D010047:Ovalbumin / Q000276:immunology / Q000378:metabolism; D010446:Peptide Fragments / Q000097:blood / Q000276:immunology* / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011961:Receptors, Fc / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000235:genetics; D014162:Transfection; D014443:Tyrosine / Q000235:genetics / Q000276:immunology
chemical_list: D064413:3-Phosphoinositide-Dependent Protein Kinases; D015703:Antigens, CD; D002867:Chromones; D004791:Enzyme Inhibitors; D000949:Histocompatibility Antigens Class II; D007070:Immunoglobulin A; D009025:Morpholines; D010047:Ovalbumin; D010446:Peptide Fragments; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011961:Receptors, Fc; D011971:Receptors, Immunologic; D014443:Tyrosine; C036832:Fc(alpha) receptor; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494918:AKT1 protein, human; C578562:PDPK1 protein, human; C578564:Pdpk1 protein, mouse