Inhibition of hepatic mitochondrial aldehyde dehydrogenase by carbon tetrachloride through JNK-mediated phosphorylation.
The aim of this study was to investigate the mechanism of inhibition of mitochondrial aldehyde dehydrogenase (ALDH2) by carbon tetrachloride (CCl(4)). CCl(4) administration caused marked hepatocyte ballooning and necrosis in the pericentral region. CCl(4) also inhibited hepatic ALDH2 activity in a time-dependent manner without altering the protein level, suggesting ALDH2 inhibition through covalent modifications such as phosphorylation by JNK. To demonstrate phosphorylation, the isoelectric point (pI) of ALDH2 in CCl(4)-exposed rats was compared to that of untreated controls. Immunoblot analysis revealed that immunoreactive ALDH2 bands in CCl(4)-exposed rats were shifted to acidic pI ranges on two-dimensional electrophoresis (2-DE) gels. Incubation with alkaline phosphatase significantly restored the suppressed ALDH2 activity with a concurrent alkaline pI shift of the ALDH2 spots. Both JNK and activated JNK were translocated to mitochondria after CCl(4) exposure. In addition, incubation with catalytically active JNK led to significant inhibition of ALDH2 activity, with an acidic pI shift on 2-DE gels. Furthermore, immunoprecipitation followed by immunoblot analysis with anti-phospho-Ser-Pro antibody revealed phosphorylation of a Ser residue(s) of ALDH2. These results collectively indicate a novel underlying mechanism by which CCl(4) exposure activates JNK, which translocates to mitochondria and phosphorylates ALDH2, contributing to inhibition of ALDH2 activity accompanied by decreased cellular defense capacity and increased lipid peroxidation.
Moon
Kwan-Hoon
KH
Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD 20892-9410, USA.
Lee
Young-Mi
YM
Song
Byoung-Joon
BJ
D000444:Aldehyde Dehydrogenase / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D000071396:Aldehyde Dehydrogenase, Mitochondrial; D000818:Animals; D002251:Carbon Tetrachloride / Q000494:pharmacology*; D015151:Immunoblotting; D047468:Immunoprecipitation; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008297:Male; D008930:Mitochondria, Liver / Q000201:enzymology*; D024101:Mitochondrial Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D018384:Oxidative Stress; D010766:Phosphorylation / Q000187:drug effects; D021381:Protein Transport; D051381:Rats; D017207:Rats, Sprague-Dawley
D024101:Mitochondrial Proteins; D002251:Carbon Tetrachloride; D000444:Aldehyde Dehydrogenase; D000071396:Aldehyde Dehydrogenase, Mitochondrial; C505112:Aldh2 protein, rat; D048031:JNK Mitogen-Activated Protein Kinases