FAD-dependent regulation of transcription, translation, post-translational processing, and post-processing stability of various mitochondrial acyl-CoA dehydrogenases and of electron transfer flavoprotein and the site of holoenzyme formation.
The most prominent biochemical consequence of riboflavin deficiency in rats is a drastic decrease in various acyl-CoA dehydrogenase activities, especially that of short chain and isovaleryl-CoA dehydrogenase (IVD). As a result, oxidation of fatty acids and leucine is severely inhibited. We studied the effects of FAD at various stages of acyl-CoA dehydrogenase biogenesis. Immunoblot revealed severe losses of various acyl-CoA dehydrogenases and electron transfer flavoprotein in riboflavin-deficient rat liver mitochondria. The decreases in IVD and short chain acyl-CoA dehydrogenase were particularly severe, reaching values of 17 and 34% of controls, respectively. With the exception of IVD, the rate of in vitro transcription of the respective genes and the amounts of mRNAs of these flavoproteins in tissues increased 3-8.5-fold over controls. The amount of IVD mRNA and its transcription rate remained unchanged, suggesting that IVD expression is regulated separately from other acyl-CoA dehydrogenases. When riboflavin was depleted, in vitro translation of acyl-CoA dehydrogenase and electron transfer flavoprotein alpha-subunit mRNAs was moderately inhibited. Translation of non-flavoproteins was also inhibited. The stability of precursor acyl-CoA dehydrogenases and their mitochondrial import/processing were unaffected. However, mature acyl-CoA dehydrogenases degraded markedly faster in deficient mitochondria than in controls. Regardless of whether precursors were translated under riboflavin-depleted or riboflavin replete conditions, mature acyl-CoA dehydrogenases survived well when imported into normal mitochondria but degraded faster when imported into deficient mitochondria. These findings indicate that FAD ligand binds to mature acyl-CoA dehydrogenase inside the mitochondria.
Nagao
M
M
Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06510.
Tanaka
K
K
D044944:Acyl-CoA Dehydrogenases / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D044927:Electron-Transferring Flavoproteins; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism / Q000494:pharmacology*; D005420:Flavoproteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D050769:Isovaleryl-CoA Dehydrogenase; D007700:Kinetics; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D009954:Ornithine Carbamoyltransferase / Q000096:biosynthesis / Q000235:genetics; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors; D014176:Protein Biosynthesis / Q000187:drug effects*; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012156:Reticulocytes / Q000187:drug effects / Q000378:metabolism; D012257:Riboflavin Deficiency / Q000201:enzymology*; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects*
D044927:Electron-Transferring Flavoproteins; D005420:Flavoproteins; D012333:RNA, Messenger; D005182:Flavin-Adenine Dinucleotide; D010088:Oxidoreductases; D044944:Acyl-CoA Dehydrogenases; D044925:Oxidoreductases Acting on CH-CH Group Donors; D050769:Isovaleryl-CoA Dehydrogenase; D009954:Ornithine Carbamoyltransferase