P43405

Syk (spleen tyrosine kinase) is a 635 amino acid protein that contains one protein kinase domain and two SH2 domains, positioning Syk as a crucial member of the protein kinase superfamily. Syk plays a vital role in B cell signaling by acting as a positive effector of B cell antigen receptor (CD79)-stimulated responses, facilitating calcium ion movement through two distinct phospho-regulated pathways. When unphosphorylated, calcium ions traverse a phosphoinositide 3-kinase-dependent pathway, while phosphorylation at tyrosine residues 348 and 352 shifts calcium flow to a phospholipase C gamma-dependent pathway. This regulatory mechanism is essential for various cellular processes, including differentiation, phagocytosis, proliferation, and B cell development. Syk expression is upregulated in T cell lymphoma, indicating potential involvement in tumorigenesis.