Definition of amino acids sufficient for plasma membrane association of CD45 and CD45-associated protein.
The transmembrane protein tyrosine phosphatase CD45 functions to activate Src-family member kinase activity in T lymphocytes. The inability to activate p56(lck) in CD45-deficient cells results in a higher threshold of signaling through the T cell receptor. The lymphoid-specific CD45-associated protein, CD45AP, interacts with CD45 through transmembrane interactions. Cells lines and mice deficient in CD45 express CD45AP mRNA, yet the protein is poorly expressed, indicating that CD45 is required for efficient expression of CD45AP. Pulse-chase analysis indicates that CD45 associates with CD45AP within minutes of biosynthesis. Cell surface labeling and coimmunoprecipitation demonstrate that CD45AP associates with surface-expressed CD45. Therefore, CD45AP is localized to the plasma membrane. To further characterize this interaction, chimeric proteins containing mutations in CD45 transmembrane regions were expressed, and their ability to associate with CD45AP was determined. Alanine-scan mutations of the CD45 transmembrane region demonstrate that no single amino acid is essential for the interaction with CD45AP. However, the expression of chimeric transmembrane regions indicates that a minimum of three and a maximum of eight amino acids in this region are sufficient to allow interaction with CD45AP.
Cahir McFarland
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ED
Howard Hughes Medical Institute, Department of Pathology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Pingel
J
J
Thomas
M L
ML
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D017493:Leukocyte Common Antigens / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins; D051379:Mice; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism
D000596:Amino Acids; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C090519:PTPRCAP protein, human; D010750:Phosphoproteins; C513303:Ptprcap protein, mouse; D012333:RNA, Messenger; D017493:Leukocyte Common Antigens