Alcohol dehydrogenase (ADH) and mitochondrial aldehyde dehydrogenase (ALDH2) are responsible for the bulk of ethanol metabolism. In the past we have studied the regulation of hepatic ADH activity by hormones. We will conclude studies on glucocorticoid regulation of ADH expression. We have found that kidney ADH mRNA and activity are induced by estradiol via stabilization of the mRNA. We will study this further by examining RNA binding proteins in renal tubule extracts. In addition, we will continue studies on the effect of ethanol on gluconeogenesis and ammoniagenesis by isolated kidney tubules. These experiments may give us insight into novel mechanisms by which ADH expression can be regulated, and may indicate that alcohol has effects on renal metabolism that could influence carbohydrate and acid-base balance. We will extend this project to study the regulation of expression of ALDH2. ALDH*2 mutation, which causes the flush reaction, is the best characterized factor that influences drinking behavior. Individuals with the flush reaction are protected against the development of alcoholism; however, there is wide variability in the intensity of flushing and in peak blood acetaldehyde levels achieved. To understand this variation, we will characterize the promoter region of the gene by transfection and DNA-protein binding studies. We will also search for variations in the ALDH2 promoter among individuals with the flush reaction; variants will then be tested for altered function. Flushing after alcohol drinking is also reported by individuals (Asians and non-Asians) who lack the ALDH2*2 mutation. We will search for additional mutations in the ALDH2 gene in these individuals by amplifying ALDH2 exons followed by electrophoretic analysis to find differences in base composition. Any exons with different mobility will then be sequenced. We will also address the question of why the ALDH2*2 mutation is dominant. Our hypothesis is that the mutation may interfere with mRNA stability, transport of the nascent peptide into the mitochondrion, or the assembly of the tetramer in the matrix space. We will transfect ALDH2 cDNAs corresponding to the active and inactive alleles into tissue.culture cells and determine mRNA stabilities, cytosolic and mitochondrial levels of ALDH2 subunits, and ALDH2 activity. These studies will expand our knowledge of the enzymology of ALDH2 and the role of acetaldehyde metabolism in the predisposition to or protection from alcoholism.
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