TEC kinase family has five family members, TEC, BTK, ITK, RLK and BMX, which share similar protein structure and sequence similarity. TEC is the first member identified in this family, which has high expression in spleen, kidney, liver and heart. Since many family members show high expression in hematopoietic cells, presumably TEC kinase family has functions in regulating processes of blood cells.
Protein structure of TEC family kinases are closely related to SRC family, all of which compose a specific N-terminal domain, SH3 (SRC homology 3), SH2 domain and kinase domain. For ITK, BTK and TEC, there is a TEC-homology domain which has one or two proline-rich regions (PRRs) in front of SH3. A pleckstrin-homology domain is a unique structure for TEC family members in tyrosine kinases, which has different specificity toward phospholipids. This structure can recruit TEC kinases to the plasma membrane through binding to the phospholipids. Instead of having a pleckstrin-homology domain, the atypical TEC kinase RLK has a palmitoylated string of cystein residues, which also results in constitutive membrane association of RLK without binding to phospholipids.
Since Tec, ITK and RLK kinases are found in T cells, it indicates a role of TEC kinases in T-cell development. For example, ITK is the major TEC kinase expressed by naïve mouse T cells with less expression of RLK and TEC. During T cell activation, ITK expression is increased in Th2 cells with decreased expression of RLK in Th1 cells. BTK is widely expressed in various hematopoetic cells, such as B cells but not t cells. Mice with Btk knock-out showed similar phenotype as xid mice, which suggest a role for BTK in B-cell signaling.
|TEC Kinase list|
|BTK/Bruton Tyrosine Kinase||BMX||ITK/ITK Kinase|