p38-2, a novel mitogen-activated protein kinase with distinct properties.
Mitogen-activated protein (MAP) kinases are involved in many cellular processes. Here we describe the cloning and characterization of a new MAP kinase, p38-2. p38-2 belongs to the p38 subfamily of MAP kinases and shares with it the TGY phosphorylation motif. The complete p38-2 cDNA was isolated by polymerase chain reaction. It encodes a 364-amino acid protein with 73% identity to p38. Two shorter isoforms missing the phosphorylation motif were identified. Analysis of various tissues demonstrated that p38-2 is differently expressed from p38. Highest expression levels were found in heart and skeletal muscle. Like p38, p38-2 is activated by stress-inducing signals and proinflammatory cytokines. The preferred upstream kinase is MEK6. Although p38-2 and p38 phosphorylate the same substrates, the site specificity of phosphorylation can differ as shown by two-dimensional phosphopeptide analysis of Sap-1a. Additionally, kinetic studies showed that p38-2 appears to be about 180 times more active than p38 on certain substrates such as ATF2. Both kinases are inhibited by a class of pyridinyl imidazoles. p38-2 phosphorylation of ATF2 and Sap-1a but not Elk1 results in increased transcriptional activity of these factors. A sequential kinetic mechanism of p38-2 is suggested by steady state kinetic analysis. In conclusion, p38-2 may be an important component of the stress response required for the homeostasis of a cell.
Pubmed ID: 9235954 RIS Download
Activating Transcription Factor 2 | Adult | Amino Acid Sequence | Calcium-Calmodulin-Dependent Protein Kinases | Cyclic AMP Response Element-Binding Protein | DNA, Complementary | Humans | Kinetics | MAP Kinase Kinase 6 | MAP Kinase Kinase Kinase 1 | Molecular Sequence Data | Phosphorylation | Protein Kinases | Protein-Serine-Threonine Kinases | RNA, Messenger | Transcription Factors