CD45

Protein tyrosine phosphatase, receptor type, C
PDB rendering based on 1ygr.
Available structures: 1ygr, 1ygu
Identifiers
Symbol(s)	PTPRC; LCA; B220; CD45; GP180; LY5; T200
External IDs	OMIM: 151460 MGI: 97810 Homologene: 2126
Gene Ontology Molecular Function: • protein tyrosine phosphatase activity • receptor activity • transmembrane receptor protein tyrosine phosphatase activity • hydrolase activity • protein kinase binding Cellular Component: • integral to plasma membrane • focal adhesion Biological Process: • negative regulation of T cell mediated cytotoxicity • negative regulation of cytokine and chemokine mediated signaling pathway • negative regulation of protein kinase activity • protein amino acid dephosphorylation • cell surface receptor linked signal transduction • T cell differentiation • B cell proliferation • positive regulation of T cell proliferation • positive regulation of protein kinase activity • T cell receptor signaling pathway • B cell receptor signaling pathway • positive regulation of antigen receptor-mediated signaling pathway • release of sequestered calcium ion into cytosol • defense response to virus • regulation of cell cycle
RNA expression pattern
Additional recommended knowledge Essential Laboratory Skills Guide Daily Sensitivity Test Don't let static charges disrupt your weighing accuracy More reference expression data
Orthologs
	Human	Mouse
Entrez	5788	19264
Ensembl	ENSG00000081237	ENSMUSG00000026395
Uniprot	P08575	Q5XFY7
Refseq	NM_002838 (mRNA) NP_002829 (protein)	NM_011210 (mRNA) NP_035340 (protein)
Location	Chr 1: 196.87 - 196.99 Mb	Chr 1: 139.88 - 139.99 Mb
Pubmed search	[1]	[2]

In immunology, the CD45 antigen (CD stands for cluster of differentiation) is a protein which was originally called leukocyte common antigen.

It is a type I transmembrane protein which is in various forms present on all differentiated hematopoietic cells except erythrocytes and plasma cells that assists in the activation of those cells (a form of co-stimulation).

It is expressed in lymphomas, B-cell chronic lymphocytic leukemia, hairy cell leukemia, and acute nonlymphocytic leukemia.

The CD45 family consists of multiple members that are all products of a single complex gene. This gene contains 34 exons and three exons of the primary transcripts are alternatively spliced to generate up to eight different mature mRNAs and after translation eight different protein products. This three exons generate the RA, RB and RC isoforms.

Various isoforms of CD45 exist: CD45RA, CD45RB, CD45RC, CD45RAB, CD45RAC, CD45RBC, CD45RO, CD45R (ABC). CD45 is also highly glycosylated. CD45R is the longest protein and migrates at 200 kDa when isolated from T cells. B cells also express CD45R with heavier glycosylation, bringing the molecular weight to 220 kDa, hence the name B220; B cell isoform of 220 kDa. B220 expression is not restricted to B cells and can also be expressed on activated T cells, on a subset of dendritic cells and other antigen presenting cells.

Naive T lymphocytes express large CD45 isoforms and are usually positive for CD45RA. Activated and memory T lymphocytes express the shortest CD45 isoform, CD45RO, which lacks RA, RB and RC exons. This shortest isoform facilitates T cell activation.

The cytoplasmic domain of CD45 is one of the largest known and it has an intrinsic phosphatase activity that removes an inhibitory phosphate group on a tyrosine kinase called Lck (in T cells) or Syk (in B cells) and activates it.

References

Further reading