title: A novel regulatory mechanism of the mitochondrial Ca2+ uniporter revealed by the p38 mitogen-activated protein kinase inhibitor SB202190.
abstract: It is widely acknowledged that mitochondrial Ca2+ uptake modulates the cytosolic [Ca2+] ([Ca2+]c) acting as a transient Ca2+ buffer. In addition, mitochondrial [Ca2+] ([Ca2+]M) regulates the rate of respiration and may trigger opening of the permeability transition pore and start apoptosis. However, no mechanism for the physiological regulation of mitochondrial Ca2+ uptake has been described. We show here that SB202190, an inhibitor of p38 mitogen-activated protein (MAP) kinase, strongly stimulates ruthenium red-sensitive mitochondrial Ca2+ uptake, both in intact and in permeabilized HeLa cells. The [Ca2+]M peak induced by agonists was increased about fourfold in the presence of the inhibitor, with a concomitant reduction in the [Ca2+]c peak. The stimulation occurred fast and was rapidly reversible. In addition, experiments in permeabilized cells perfused with controlled [Ca2+] showed that SB202190 stimulated mitochondrial Ca2+ uptake by more than 10-fold, but only in the physiological [Ca2+]c range (1-4 mM). Other structurally related p38 MAP kinase inhibitors (SB203580, PD169316, or SB220025) produced little or no effect. Our data suggest that in HeLa cells, a protein kinase sensitive to SB202190 tonically inhibits the mitochondrial Ca2+ uniporter. This novel regulatory mechanism may be of paramount importance to modulate mitochondrial Ca2+ uptake under different physiopathological conditions.
mesh_terms: D002118:Calcium / Q000032:analysis / Q000378:metabolism; D015220:Calcium Channels; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D006367:HeLa Cells; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D017136:Ion Transport; D007700:Kinetics; D008928:Mitochondria / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors*; D008954:Models, Biological; D011725:Pyridines / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D004791:Enzyme Inhibitors; D007093:Imidazoles; D024101:Mitochondrial Proteins; D011725:Pyridines; C034703:mitochondrial calcium uniporter; D006632:Histamine; D002217:Carbachol; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole; D002118:Calcium