Human microRNA (miR29b) expression controls the amount of branched chain α-ketoacid dehydrogenase complex in a cell

Abstract

Branched chain amino acids (BCAAs) play critical roles in cell and tissue functions in addition to being important components of protein structure. The multifunctional roles speak to the need for maintaining tight control of their concentration within cells. As the BCAA cannot be made de novo in mammals, their cellular concentration is a function of dietary intake, endogenous protein turnover and catabolism of the three amino acids. The branched chain alpha-ketoacid dehydrogenase (BCKD) complex commits the BCAA to degradation and thus is vital in controlling their concentration within a cell. In mammals, BCKD activity state depends on the presence of a covalently bound phosphate on one protein component of the complex. Phosphate is added to the protein through the action of the complex-specific kinase and results in BCKD inactivation. Here, we demonstrate that another reaction plays a role in determining the total amount of BCKD present in a cell. The microRNA (miR29b) molecule tested is targeted to the mRNA for the dihydrolipoamide branched chain acyltransferase component of BCKD and prevents translation when bound. This is the first demonstration of the use of a microRNA to exert control on a metabolic pathway of amino acid catabolism in mammals and offers an explanation for the observed differences in the amount of the BCKD complex present in different tissues and under varying nutritional states.

MicroRNA-370 controls the expression of MicroRNA-122 and Cpt1α and affects lipid metabolism

“…HepG2 cells were transfected with 50 nM miR-122 or miR-370, and 24 h later, were washed with PBS prior to labeling in DMEM (1 ml/well) containing stages of investigation, and our knowledge of the underlying mechanism is limited ( 31,32 ). Known examples include the regulation of insulin secretion by miR-375, which targets myotrophin mRNA ( 28 ); miR-9, which targets granulophilin and other pancreatic and brain mRNAs involved in exocytosis ( 20,33 ); and miR-29b and miR-122, which control genes that affect amino acid ( 34 ) and lipid ( 35,36 ) metabolism, respectively. miR expression signatures have been associated with well-defi ned clinico-pathological features and disease outcome (37)(38)(39)(40)(41)(42).…”

Energizing miRNA research: A review of the role of miRNAs in lipid metabolism, with a prediction that miR-103/107 regulates human metabolic pathways

“…One of the few published examples of miRNAs regulating a metabolic pathway per se involves miR-29b, which Mersey et al [57] demonstrate may be involved in the metabolism of amino acids in HEK 293 cells. This activity evidently occurs through regulation of the mRNA for the dihydrolipoamide branched chain acyltransferase subcomponent of the branched chain alphaketoacid dehydrogenase (BCKD) complex.…”

Potential relevance of microRNAs in inter-species epigenetic communication, and implications for disease pathogenesis

“…72 (Fig. 1) Another bovine derived miRNA, miR-200c which is also identical to its human counterpart 66 targets zinc finger E-box binding homeobox 1 and 2 (ZEB1 and ZEB2) proteins that are transcriptional repressors of E-cadherin, 73 and thus acts as a tumor suppressor in different models.…”