Differential regulation of human ALAS1 mRNA and protein levels by heme and cobalt protoporphyrin

• Published in: Molecular and cellular biochemistry Vol. 319; no. 1-2; pp. 153 - 161
• Main Authors: Zheng, Jianyu, Shan, Ying, Lambrecht, Richard W, Donohue, Susan E, Bonkovsky, Herbert L
• Format: Journal Article
• Language: English
• Published: Boston Boston : Springer US 01.12.2008; Springer US; Springer Nature B.V
• Subjects: 5-Aminolevulinate Synthetase - biosynthesis; Biochemistry; Biomedical and Life Sciences; Biosynthesis; Cardiology; Cell Line, Tumor; Cobalt; Cycloheximide - pharmacology; Dactinomycin - pharmacology; Down-Regulation - drug effects; Enzymes; Gene Expression Regulation, Enzymologic - drug effects; Half-Life; Heme - pharmacology; Hepatocytes - enzymology; Humans; Life Sciences; Medical Biochemistry; Mitochondrial Proteins - biosynthesis; Molecular biology; Nucleic Acid Synthesis Inhibitors - pharmacology; Oncology; Porphyria, Acute Intermittent - drug therapy; Porphyria, Acute Intermittent - enzymology; Protein Synthesis Inhibitors - pharmacology; Proteins; Protoporphyrins - pharmacology; Protoporphyrins - therapeutic use; Ribonucleic acid; RNA; RNA, Messenger - biosynthesis; 5-Aminolevulinic acid synthase 1 (ALAS1); Cobalt protoporphyrin (CoPP); Heme; Protein stability; HepG2 cells; Huh-7 cells; mRNA stability
• ISSN: 0300-8177; 1573-4919
• DOI: 10.1007/s11010-008-9888-0

5-Aminolevulinic acid synthase 1 (ALAS1) is the first and rate-controlling enzyme of heme biosynthesis. This study was to determine the effects of heme and selected nonheme metalloporphyrins on human ALAS1 gene expression in hepatocytes. We found that, upon heme and cobalt protoporphyrin (CoPP) treatments, ALAS1 mRNA levels were down-regulated significantly by ca. 50% or more. Measurement of mRNA in the presence of actinomycin D showed that these down-regulations were due to the decreases in mRNA half-lives. Furthermore, the levels of mitochondrial mature ALAS1 protein were down-regulated by 60-70%, but those of the cytosolic precursor protein were up-regulated by 2-5-fold. Measurement of protein in the presence of cycloheximide (CHX) suggests that elevation of the precursor form is due to the increase in protein half-lives. These results provide novel insights into the mechanisms of heme repressional effects on ALAS1 and provide a rationale for further investigation of CoPP as a therapeutic agent for acute porphyric syndromes.