Lck Rabbit Recombinant mAb detects endogenous levels of total Lck.

Lck is a member of the Src family of protein tyrosine kinase and plays key roles in T lymphocyte activation and differentiation. It is associated with a variety of cell surface receptors (such as CD4 and CD8) and is critical for signal transduction from the T-cell antigen receptor (TCR). Association of the TCR with a peptide antigen-bound MHC complex facilitates the interaction of CD4 and CD8 with MHC class II and class I molecules, respectively, and thereby recruits the associated Lck to the vicinity of the TCR/CD3 complex. Lck then phosphorylates tyrosine residues within the immunoreceptor tyrosine-based activation motifs (ITAMs) in the cytoplasmic tails of the TCRζ-chains and CD3 subunits. The phospho-ITAMs serve as docking sites for Src homology domain 2 (SH2)-containing molecules, predominantly ZAP-70 and Syk. Only then can ZAP-70 undergo tyrosine phosphorylation, become enzymatically active and further phosphorylate downstream effector molecules. In addition, Lck contributes to signaling by other receptor molecules. It associates directly with the cytoplasmic tail of CD20 and thus plays a role in the interleukin 2 (IL-2) receptorlinked signaling pathway that controls the T-cell proliferative response. Binding of IL-2 to its receptor results in increased catalytic activity of Lck. Lck is expressed at all stages of thymocyte development and is required for the regulation of maturation events that are governed by both pre-TCR and mature αβ TCR. Lck resides predominantly in the cytosol where it interacts with the inner leaflet of the plasma membrane via its hydrophobic myristilated N-terminus. Various cellular proteins can interact with Lck, including cell surface receptor molecules (CD2, CD4, CD5, CD8, CD44, CD45, CD122, and the IL-7 receptor, p90), effector molecules (PI3K, PI4K, Vav, ras GAP, p120, LckBP1), glycophosphatidylinositol-anchored proteins, and protein kinases (Cdc2, Raf-1, raf-related p110, ZAP-70, Syk)