Src

Src family kinase (SFK) is a family of non-receptor tyrosine kinases including nine members: Src, Yes, Fyn, and Fgr, forming the SrcA subfamily, Lck, Hck, Blk, and Lyn in the SrcB subfamily, and Frk in its own subfamily. In immune cells, Src-family kinases (SFKs) have been implicated as critical regulators of a large number of intracellular signaling pathways. Src-family kinases (SFKs) occupy a proximal position in numerous signaling transduction cascades including those emanating from the T and B cell antigen receptors, Fc receptors, growth factor receptors, cytokine receptors, and integrins. In addition to these positive regulatory roles, Src-family kinases (SFKs) can also function as negative regulators of cellular signaling by phosphorylating immunoreceptor tyrosine-based inhibitory motifs (ITIMs) on inhibitory receptors, resulting in recruitment and activation of inhibitory molecules such as the phosphatases SHP-1 and SH2 containing 5′ inositol phosphatase (SHIP-1).