Down‐regulation of the mitochondrial pathway for de novo fatty acid synthesis compromises lipoylation pathways in human embryonic kidney cells

Abstract

Recent studies have demonstrated the presence of freestanding enzymes in the mitochondrial matrix that constitute a pathway for de novo biosynthesis of fatty acids. One of the major products, octanoyl‐ACP, is utilized as a precursor for lipoyl moieties that are essential for functioning of several key mitochondrial enzymes. The objective of this study was to assess the importance of this pathway to mitochondrial integrity by down‐regulating formation of the ACP component. HEK293 cells were transfected with siRNA targeting mitochondrial ACP. Knock‐down efficiency was monitored by quantitative real‐time RT‐PCR and protein lipoylation was assayed by Western blotting, using lipoic acid antibodies. Preliminary results show that exposure to siRNA reduced ACP mRNA levels by 95%, significantly retarded cell growth and lowered lipoylation of the E2 subunits of both pyruvate and oxoglutarate dehydrogenases by 90%. Thus the de novo synthesis of fatty acids in the mitochondrial matrix appears crucial for maintenance of mitochondrial integrity. Supported by NIH grant GM06717