title: Characterization of the interaction between CD45 and CD45-AP.
abstract: CD45, a leukocyte-specific transmembrane protein tyrosine phosphatase, is required for critical signal transduction pathways in immune responses. To elucidate the molecular interactions of CD45 with other proteins involved in CD45-mediated signal transduction pathways, we have recently cloned a 30-kDa phosphorylated protein, CD45-AP, which specifically associates with CD45. Binding analysis employing several deleted or chimeric forms of CD45-AP and CD45 demonstrated that the potential transmembrane segment of CD45-AP bound to the transmembrane portion of CD45. CD45-AP was found in particulate fractions of lymphocytes along with CD45, indicating that it is likely to be a transmembrane protein. In addition, CD45-AP was resistant to proteolysis by tosylphenylalanyl chloromethyl ketone-treated trypsin applied to intact cells. This is consistent with the most likely membrane orientation of CD45-AP predicted from the amino acid sequence, that is, only a short amino-terminal segment of CD45-AP is extracellular. We propose that CD45-AP interacts with CD45 at the plasma membrane and that the bulk of CD45-AP located in the cytoplasm act as an adapter which directs the interaction between CD45 and other molecules involved in CD45-mediated signal transduction pathways.
authors.affiliation: Department of Pathology, Roger Williams Medical Center-Brown University, Providence, Rhode Island 02908, USA.
authors.forename: K
authors.initials: K
authors.lastname: Kitamura
authors.forename: A
authors.initials: A
authors.lastname: Maiti
authors.forename: D H
authors.initials: DH
authors.lastname: Ng
authors.forename: P
authors.initials: P
authors.lastname: Johnson
authors.forename: A L
authors.initials: AL
authors.lastname: Maizel
authors.forename: A
authors.initials: A
authors.lastname: Takeda
mesh_terms: D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D007739:L Cells; D017493:Leukocyte Common Antigens / Q000378:metabolism*; D008565:Membrane Proteins; D051379:Mice; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D014176:Protein Biosynthesis; D011994:Recombinant Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010750:Phosphoproteins; C513303:Ptprcap protein, mouse; D011994:Recombinant Proteins; D017493:Leukocyte Common Antigens