CD45 (Cluster of Differentiation 45), also known as protein tyrosine phosphatase receptor type C (PTPRC), is a transmembrane protein tyrosine phosphatase critical for lymphocyte function[@biology2020]. As a major phosphatase in immune cells, CD45 regulates signal transduction through the T-cell receptor (TCR) and B-cell receptor (BCR), making it essential for adaptive immunity[@ptprc2021]. In the nervous system, CD45 is expressed on [microglia](/cell-types/microglia-neuroinflammation) and certain [neurons](/entities/neurons), where it plays roles in neuroinflammation and neuronal signaling[@cns2019].
Gene and Expression
The human PTPRC gene is located on chromosome 1q31-32 and encodes a protein of 1,268-2,047 amino acids depending on isoform. Multiple isoforms are generated through alternative splicing:
CD45 (Cluster of Differentiation 45), also known as protein tyrosine phosphatase receptor type C (PTPRC), is a transmembrane protein tyrosine phosphatase critical for lymphocyte function[@biology2020]. As a major phosphatase in immune cells, CD45 regulates signal transduction through the T-cell receptor (TCR) and B-cell receptor (BCR), making it essential for adaptive immunity[@ptprc2021]. In the nervous system, CD45 is expressed on [microglia](/cell-types/microglia-neuroinflammation) and certain [neurons](/entities/neurons), where it plays roles in neuroinflammation and neuronal signaling[@cns2019].
Gene and Expression
The human PTPRC gene is located on chromosome 1q31-32 and encodes a protein of 1,268-2,047 amino acids depending on isoform. Multiple isoforms are generated through alternative splicing:
Immune cells: T cells, B cells, NK cells, macrophages
Brain: Microglia, some neurons, endothelial cells
Isoform patterns: Different isoforms innaive vs. memory T cells
Development: Regulated expression during hematopoiesis[@ptprc2020]
Structure
CD45 has a complex multi-domain structure:
Extracellular domain: Variable due to alternative splicing
Single transmembrane domain: Connects to cytoplasmic portion
Cytoplasmic domain: Contains two phosphatase domains (D1 and D2)
Fibronectin type III repeats: Three repeats in extracellular region