CD3 epsilon Protein, Canine (HEK293, His)

The CD3 epsilon protein is an integral component of the TCR-CD3 complex located on the T-lymphocyte cell surface, playing a pivotal role in adaptive immune responses. When activated by antigen-presenting cells (APCs), the T-cell receptor (TCR) initiates signaling pathways transmitted across the cell membrane by the CD3 chains CD3D, CD3E, CD3G, and CD3Z, all of which contain immunoreceptor tyrosine-based activation motifs (ITAMs) in their cytoplasmic domain. Upon TCR engagement, these ITAMs undergo phosphorylation by Src family protein tyrosine kinases LCK and FYN, activating downstream signaling pathways. Beyond its role in signal transduction for T-cell activation, CD3E is indispensable for proper T-cell development and plays a crucial role in initiating TCR-CD3 complex assembly by forming the two heterodimers CD3D/CD3E and CD3G/CD3E. CD3E also participates in the internalization and cell surface down-regulation of TCR-CD3 complexes through endocytosis sequences present in its cytosolic region. The TCR-CD3 complex consists of CD3D/CD3E and CD3G/CD3E heterodimers that associate with TCRalpha and TCRbeta, forming trimers. The hexamer interacts with CD3Z homodimer to complete the TCR-CD3 complex, with the flexibility for TCRalpha and TCRbeta substitution by TCRgamma and TCRdelta. CD3E further interacts with CD6, NCK1, and NUMB, the latter being crucial for TCR-CD3 internalization and subsequent degradation. This intricate network underscores the multifunctional role of CD3E in orchestrating T-cell responses.