TRPM7 activates m-calpain by stress-dependent stimulation of p38 MAPK and c-Jun N-terminal kinase.
TRPM7 is a Ca(2)(+)-permeant and Mg(2)(+)-permeant ion channel in possession of its own kinase domain. In a previous study, we showed that overexpression of the channel-kinase in HEK-293 cells produced cell rounding and loss of adhesion, which was dependent on the Ca(2+)-dependent protease m-calpain. The TRPM7-elicited change in cell morphology was channel-dependent and occurred without any significant increase in cytosolic Ca(2+). Here we demonstrate that overexpression of TRPM7 increased levels of cellular reactive oxygen species (ROS) and nitric oxide, causing the activation of p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK). Application of inhibitors of p38 MAPK and JNK blocked TRPM7-induced cell rounding and activation of m-calpain, without affecting the phosphorylation state of the protease. Overexpression of TRPM7 increased intracellular Mg(2+); however, when the concentration of either external Ca(2+) or Mg(2+) was increased to favor the permeation of one divalent cation over the other, a similar increase in cell rounding and calpain activity was detected, indicating that TRPM7-mediated activation of m-calpain is not dependent on the nature of the divalent conducted by the channel. Application of inhibitors of nitric oxide synthase and mitochondrial-derived ROS reduced TRPM7-induced increases in nitric oxide and ROS production, blocked the change in cell morphology, and reduced cellular calpain activity. Collectively, our data reveal that excessive TRPM7 channel activity causes oxidative and nitrosative stresses, producing cell rounding mediated by p38 MAPK/JNK-dependent activation of m-calpain.
Su
Li-Ting
LT
Department of Pharmacology, UMDNJ-Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA.
Chen
Hsiang-Chin
HC
González-Pagán
Omayra
O
Overton
Jeffrey D
JD
Xie
Jia
J
Yue
Lixia
L
Runnels
Loren W
LW
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000378:metabolism*; D002448:Cell Adhesion; D002460:Cell Line; D048430:Cell Shape; D025461:Feedback, Physiological; D015870:Gene Expression; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism; D018384:Oxidative Stress; D017346:Protein Serine-Threonine Kinases; D017382:Reactive Oxygen Species / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D050053:TRPM Cation Channels / Q000235:genetics / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D017382:Reactive Oxygen Species; D011994:Recombinant Proteins; D050053:TRPM Cation Channels; D009569:Nitric Oxide; C421903:Trpm7 protein, mouse; D017346:Protein Serine-Threonine Kinases; C486583:TRPM7 protein, human; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D002154:Calpain; C449000:m-calpain; D002118:Calcium