Function
CD3E is a component of the TCR-CD3 complex found on the surface of T-lymphocytes. It plays a crucial role in the adaptive immune response. When antigen-presenting cells (APCs) activate the T-cell receptor (TCR), CD3E, along with CD3D, CD3G, and CD3Z, transmit signals across the cell membrane. All CD3 chains contain immunoreceptor tyrosine-based activation motifs (ITAMs) in their cytoplasmic domain. Upon TCR engagement, these motifs become phosphorylated by Src family protein tyrosine kinases LCK and FYN, triggering the activation of downstream signaling pathways. Beyond its role in signal transduction during T-cell activation, CD3E is essential for proper T-cell development. It initiates the assembly of the TCR-CD3 complex by forming two heterodimers: CD3D/CD3E and CD3G/CD3E. CD3E also participates in the internalization and down-regulation of TCR-CD3 complexes on the cell surface through endocytosis sequences present in its cytosolic region.