Serine / Threonine Protein Kinase Brsk2 Function Of A Preliminary Study

Protein kinases achieve post-translational modifications via the phosphorylation of serine, threonine, and tyrosine residues, which plays a role in many cellular processes such as transduction of extracellular signals, intracellular transport, and cell cvcle Droeression.cell cycle progression.We obtained the gene sequence of BRSK2 from Genbank database by electric hybridization. This gene contains an open reading frame of 2025bp, encoding 674 amino acids, mapped to human chromosome 11q15.5 and composed of 21 exons. The 19-270 amino acid residues of amino acid of BRSK2 consist of a serine/threonine protein kinase domain. According to its amino acids sequence homology of kinase domain, it is classified to AMPK subfamily of CAMK protein kinase family. The 10-674 amino acid residues of amino acid of BRSK2 consist of a KOG0588 domain related to control of cell cycle, cell division and chromosome separation. Northern analysis indicates that BRSK2 highly expresses in brain and pancreas specifically. Subcellular localization of BRSK2 is around the nucleus.Based on the homology of BRSK2 to AMPK, the substrate polypeptide of AMPK, SAMS peptide, was performed to detect the kinase activity of BRSK2. The result shows that BRSK2 phosphorelates SAMS peptide but not the mutated SAMA peptide. Further study of BRSK2 indicates that BRSK2 possesses comprehensive cell function, such as increasing the cell survival under glucose starvation, suppressing the protein synthesis, causing the cell cycle G2/M delay, activating AP1, NFAT, HSE cell signal pathways.We identified a phosphorelation site of PKA at Thr260. In vitro experiments indicate that Thr260 can be phosphorelated by PKA. The phosphorelation at Thr260 canstimulate the activity of BRSK2. When Thr260 was mutated to Alanine, The kinase activity would depress, which would cause partial loss of function of BRSK2 on stimulating cell survival, control of protein synthesis, G2/m stage and AP1 activation.It has been reported that LKB1 can phosphorelate and activate BRSK2 at Thr174 site, whose mutation prevented activation of BRSK2. The effect of Thr174 mutation on the cellular function of BRSK2 was compared to that of Thr260 mutation. The results indicate that the Thrl74 mutation causes the complete loss of function of BRSK2, whereas Thr260 mutation causes the partial loss of function. These results suggest that the phosphorelation at Thr174 is essential for activity and function of BRSK2, while phosphorelation at Thr260 modulates the kinase activity and the phosphorelation at Thr174.