CD45, also known as T200 or the Leukocyte Common Antigen (LCA), is encoded by the Protein Tyrosine Phosphatase Receptor type C (PTPRC) gene. The protein is expressed exclusively on cells of the haematopoietic system, and is one of the most abundant leukocyte cell surface glycoproteins (1). Different isoforms of CD45 are found on specific lymphocyte sub-populations, and are generated by alternative splicing. (2). At least four variants of the human protein can be distinguished by electrophoresis, with molecular weights ranging from 180-220kDa (3). B cells have been shown to express a 220kDa protein, while thymocytes express a 180kDa variant (2).
CD45 is a member of the Protein Tyrosine Phosphatase (PTP) family, which is comprised of more than 100 human genes (4). PTPs were originally believed to be housekeeping proteins, responsible simply for the dephosphorylation of tyrosine residues, however they are now known to play key roles in signal transduction by controlling the reversible phosphorylation of their substrates.
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Immunohistochemistry-Paraffin: CD45 Antibody
The structure of CD45 is receptor-like, with an extracellular N-terminal region, a transmembrane domain, and a conserved intracellular segment containing two tandemly repeated sections each of approximately 300 residues (5). As a result of the diversity of the N-terminal region, CD45 is able to interact with different ligands and subsequently exert diverse downstream effects. One well-studied function of CD45 is its regulation of T cell activation through dephosphorylation of the tyrosine protein kinase Lck. Lck is a member of the Src family, and is expressed in the cytoplasm of lymphoid cells where it associates with the cytoplasmic portion of the CD4 and CD8 receptors. Lck plays a key role in T cell activation and differentiation (6); cells that are deficient in CD45 show increased Lck phosphorylation, and mice that are deficient in the protein demonstrate a block in thymocyte development (7).
Novus Biologicals offers CD45 reagents for your research needs including:
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Written by Emma Easthope
