title: Phosphocitrate inhibits a basic calcium phosphate and calcium pyrophosphate dihydrate crystal-induced mitogen-activated protein kinase cascade signal transduction pathway.
abstract: Calcium deposition diseases caused by calcium pyrophosphate dihydrate (CPPD) and basic calcium phosphate (BCP) crystals are a significant source of morbidity in the elderly. We have shown previously that both types of crystals can induce mitogenesis, as well as metalloproteinase synthesis and secretion by fibroblasts and chondrocytes. These responses may promote degradation of articular tissues. We have also shown previously that both CPPD and BCP crystals activate expression of the c-fos and c-jun proto-oncogenes. Phosphocitrate (PC) can specifically block mitogenesis and proto-oncogene expression induced by either BCP or CPPD crystals in 3T3 cells and human fibroblasts, suggesting that PC may be an effective therapy for calcium deposition diseases. To understand how PC inhibits BCP and CPPD-mediated cellular effects, we have investigated the mechanism by which BCP and CPPD transduce signals to the nucleus. Here we demonstrate that BCP and CPPD crystals activate a protein kinase signal transduction pathway involving p42 and p44 mitogen-activated protein (MAP) kinases (ERK 2 and ERK 1). BCP and CPPD also cause phosphorylation of a nuclear transcription factor, cyclic AMP response element-binding protein (CREB), on serine 133, a residue essential for CREB's ability to transactivate. Treatment of cells with PC at concentrations of 10(-3) to 10(-5) M blocked both the activation of p42/p44 MAP kinases, and CREB serine 133 phosphorylation, in a dose-dependent fashion. At 10(-3) M, a PC analogue, n-sulfo-2-aminotricarballylate and citrate also modulate this signal transduction pathway. Inhibition by PC is specific for BCP- and CPPD-mediated signaling, since all three compounds had no effect on serum-induced p42/P44 or interleukin-1beta induced p38 MAP kinase activities. Treatment of cells with an inhibitor of MEK1, an upstream activator of MAPKs, significantly inhibited crystal-induced cell proliferation, suggesting that the MAPK pathway is a significant mediator of crystal-induced signals.
authors.affiliation: Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
authors.forename: D
authors.initials: D
authors.lastname: Nair
authors.forename: R P
authors.initials: RP
authors.lastname: Misra
authors.forename: J D
authors.initials: JD
authors.lastname: Sallis
authors.forename: H S
authors.initials: HS
authors.lastname: Cheung
mesh_terms: D002130:Calcium Phosphates / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002131:Calcium Pyrophosphate / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002455:Cell Division; D002478:Cells, Cultured; D002951:Citrates / Q000494:pharmacology*; D003460:Crystallization; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010766:Phosphorylation; D000090063:Proto-Oncogene Mas; D015398:Signal Transduction / Q000187:drug effects; D014233:Tricarboxylic Acids / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D002130:Calcium Phosphates; D002951:Citrates; D017362:Cyclic AMP Response Element-Binding Protein; D007375:Interleukin-1; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D014233:Tricarboxylic Acids; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; C014148:phosphocitrate; C485838:calcium phosphate, monobasic, anhydrous; C039013:N-sulfo-2-aminotricarballylate; C020243:calcium phosphate; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C485829:calcium phosphate, dibasic, anhydrous; D002131:Calcium Pyrophosphate