title: Detection of restricted isoform expression and tyrosine phosphatase activity of CD45 in murine dendritic cells.
abstract: CD45 is a cell surface transmembrane tyrosine phosphatase. It is expressed as distinct protein isoforms via alternative splicing of exons 4, 5 and 6. In T and B lymphocytes, CD45 is thought to play a critical role in antigen-dependent signaling through their respective antigen receptor complexes. However, the isoform expression and enzymatic activity of CD45 in other leukocytes remains largely unknown. Here, we examine the isoform expression and phosphatase activity of CD45 in murine dendritic cells (DC). Flow cytometric double-labeling analysis and biochemical analysis of purified splenic DC CD45 demonstrate that DC express both the CD45RB and CD45R0 isoforms. Flow cytometric analyses of freshly isolated splenic DC and thymic DC also indicate the expression of CD45RB and CD45R0 on these DC populations. In addition, we find that purified splenic DC CD45 possesses a high level of intrinsic tyrosine phosphatase activity. These data therefore establish the restricted isoform expression pattern of CD45 in murine DC and demonstrate that cells lacking specific antigen receptor complexes have active tyrosine phosphatase activity associated with CD45.
authors.affiliation: Biotechnology Laboratory, University of British Columbia, Vancouver, Canada.
authors.forename: I D
authors.initials: ID
authors.lastname: Haidl
authors.forename: D H
authors.initials: DH
authors.lastname: Ng
authors.forename: S
authors.initials: S
authors.lastname: Rothenberger
authors.forename: P
authors.initials: P
authors.lastname: Johnson
authors.forename: W A
authors.initials: WA
authors.lastname: Jefferies
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D003713:Dendritic Cells / Q000201:enzymology* / Q000276:immunology; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D005091:Exons / Q000276:immunology; D005260:Female; D005434:Flow Cytometry; D007527:Isoenzymes / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D017493:Leukocyte Common Antigens / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D008297:Male; D051379:Mice; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D013154:Spleen / Q000737:chemistry / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D007527:Isoenzymes; D017493:Leukocyte Common Antigens; D017027:Protein Tyrosine Phosphatases