Activation and signaling of the p38 MAP kinase pathway

The family members of the mitogen-activated protein (MAP) kinases mediate a wide variety of cellular behaviors in response to extracellular stimuli. One of the four main sub-groups, the p38 group of MAP kinases, serve as a nexus for signal transduction and play a vital role in numerous biological processes. In this review, we highlight the known characteristics and components of the p38 pathway along with the mechanism and consequences of p38 activation. We focus on the role of p38 as a signal transduction mediator and examine the evidence linking p38 to inflammation, cell cycle, cell death, development, cell differentiation, senescence and tumorigenesis in specific cell types. Upstream and downstream components of p38 are described and questions remaining to be answered are posed. Finally, we propose several directions for future research on p38.

p38 MAP kinase is necessary for melanoma-mediated regulation of VE-cadherin disassembly

Introduction Vascular endothelial (VE)-cadherin is localized to the endothelial borders and the adherens junctions,which are regulated by changes in mitogen activated protein kinases (MAPK),GTPases,and intracellular calcium. We previously

Correlation between Expression of P38 MAPK-Signaling and uPA in Breast Cancer

OBJECTIVE To study the expression of phosphorylated p38 mitogen-activated protein kinase （p-p38） and uPA and the correlation of their expression with breast cancer clinicopathological characteristics, and to investigate the role of the p38MAPK-signaling pathway in regulating uPA expression in breast cancer cells.METHODS Immunohistochemistry （S-P） was used to test the expression of p-p38 and uPA in 60 specimens of breast cancer tissues. Western blots were adopted to detect expression of the p-p38 and uPA proteins in MDA-MB-231 and MCF-7 breast cancer cells, and uPA expression after treatment with SB203580, a specific inhibitor of p38 MAPK.RESULTS The positive rate of the p-p38 protein and uPA protein expression in the breast cancer tissues was 56.7% and 60.0%,respectively. The expression of p-p38 was positively related to the expression of uPA （r = 0.316, P 〈 0.05）. The expression of p-p38 and uPA was related to lymph node metastasis and the TNM stage （P 〈 0.05）, but it was not related to the patient＇s age or tumor size （P 〉 0.05）. The expression of p-p38 and uPA in MDA- MB-231 cells was higher than that in MCF-7 cells. SB203580 inhibited the p38 MAPK pathway and reduced uPA protein expression.CONCLUSION The p38 MAPK-signaling pathway promotes breast cancer malignant progression by up-regulating uPA expression ,and it may be an important process in breast cancer invasion and metastasis.

p38α MAP kinase phosphorylates RCAN1 and regulates its interaction with calcineurin

RCAN1, also known as DSCR1, is an endogenous regulator of calcineurin, a serine/threonine protein phosphatase that plays a critical role in many physiological processes. In this report, we demonstrate that p38a MAP kinase can phosphorylate RCAN1 at multiple sites in vitro and show that phospho-RCAN1 is a good protein substrate for calcineurin. In addition, we found that unphosphorylated RCANI noncompetitively inhibits calcineurin protein phosphatase activity and that the phosphorylation of RCAN1 by p38a MAP kinase decreases the binding affinity of RCAN1 for calcineurin. These findings reveal the molecular mechanism by which p38a MAP kinase regulates the function of RCAN1/calcineurin through phosphorylation.

Crystal structure of the p38α MAP kinase in complex with a docking peptide from TAB1

The mitogen-activated protein kinase (MAPK) p38α is a key regulator in many cellular processes, whose activity is tightly regulated by upstream kinases, phosphatases and other regulators. Transforming growth factor-β activated kinase 1 (TAK1) is an upstream kinase in p38α signaling, and its full activation requires a specific activator, the TAK1-binding protein (TAB1). TAB1 was also shown to be an inducer of p38α's autophosphorylation and/or a substrate driving the feedback control of p38α signaling. Here we determined the complex structure of the unphosphorylated p38α and a docking peptide of TAB1, which shows that the TAB1 peptide binds to the classical MAPK docking groove and induces long-range conformational changes on p38α. Our structural and biochemical analyses suggest that TAB1 is a reasonable substrate of p38α, yet the interaction between the docking peptide and p38α may not be sufficient to trigger trans-autophosphorylation of p38α.