title: Alterations in subcellular localization of p38 MAPK potentiates endothelin-stimulated COX-2 expression in glomerular mesangial cells.
abstract: Endothelin-1 (ET-1) is a potent vasoconstrictor peptide with mitogenic actions linked to activation of tyrosine kinase signaling pathways. ET-1 induces cyclooxygenase-2 (COX-2), an enzyme that converts arachidonic acid to pro-inflammatory eicosanoids. Activation of each of the three major mitogen-activated protein kinase (MAPK) pathways, ERK1/2, JNK/SAPK, and p38 MAPK (p38), have been shown to enhance the expression of COX-2. Negative regulation of MAPK may occur via a family of dual specificity phosphatases referred to as mitogen-activated protein kinase phosphatases (MKP). The goal of this work was to test the hypothesis that wild type MKP-1 regulates the expression of ET-1-induced COX-2 expression by inhibiting the activation of p38 in cultured glomerular mesangial cells (GMC). An adenovirus expressing both wild type and a catalytically inactive mutant of MKP-1 (MKP-1/CS) were constructed to study ET-1-regulated MAPK signaling and COX-2 expression in cultured GMC. ET-1 stimulated the phosphorylation of ERK and p38 alpha MAPK and induced the expression of COX-2. Expression of COX-2 was partially blocked by U0126, a MEK inhibitor, and SB 203580, a p38 MAPK inhibitor. Adenoviral expression of MKP-1/CS augmented basal and ET-1-induced phosphorylation of p38 alpha MAPK with less pronounced effects on ERK1/2 phosphorylation. Ectopic expression of wild type MKP-1 blocked the phosphorylation of p38 alpha MAPK by ET-1 but increased the phosphorylation of p38 gamma MAPK. Co-precipitation studies demonstrated association of MKP-1 with p38 alpha MAPK and ERK1/2. Immunofluorescent image analysis demonstrated trapping of phospho-p38 MAPK in the cytoplasm by MKP-1/CS/green fluorescent protein. ET-1-stimulated expression of COX-2 was increased in MKP-1/CS versus LacZ or green fluorescent protein-infected control cells. These results indicate that MKP-1 demonstrates a relative selectivity for p38 alpha MAPK versus p38 gamma MAPK in GMC and is likely to indirectly regulate the expression of COX-2.
authors.affiliation: Department of Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
authors.forename: Phillip F
authors.initials: PF
authors.lastname: Pratt
authors.forename: Dirk
authors.initials: D
authors.lastname: Bokemeyer
authors.forename: Marco
authors.initials: M
authors.lastname: Foschi
authors.forename: Andrey
authors.initials: A
authors.lastname: Sorokin
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Dunn
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D051546:Cyclooxygenase 2; D054638:Dual Specificity Phosphatase 1; D019332:Endothelin-1 / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D005920:Glomerular Mesangium / Q000166:cytology*; D017874:Immediate-Early Proteins / Q000378:metabolism / Q000502:physiology; D007527:Isoenzymes / Q000096:biosynthesis*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases; D010766:Phosphorylation; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*; D011485:Protein Binding; D054645:Protein Phosphatase 1; D021381:Protein Transport; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D018797:Cell Cycle Proteins; D019332:Endothelin-1; D017874:Immediate-Early Proteins; D007527:Isoenzymes; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; C517021:Dusp1 protein, rat; D017027:Protein Tyrosine Phosphatases