Fatty acid oxidation-respiratory chain proteins and their interactions are abnormal in end-stage cardiomyopathy.


Presented By:

Yudong Wang, Ph.D.1, Johan Palmfeldt, 2, Neils Gregersen2, Alexander M. Makhov3, James F. Conway3,
Areeg El-gharbawy1, and Jerry Vockley, M.D., Ph.D.1,4
1University of Pittsburgh School of Medicine, Department of Pediatrics, Pittsburgh, PA, United States
2Aarhus University Hospital, Aarhus, Denmark.
3University of Pittsburgh School of Medicine, Department of Structural Biology, Pittsburgh, PA, United States
4Children’s Hospital of Pittsburgh, Center for Rare Disease Therapy, Pittsburgh, PA, United States
Correspondence: Jerry Vockley, vockleyg@upmc.edu, (412) 692-7746

BACKGROUND: Fatty acid oxidation (FAO) is a major mitochondrial bioenergetic pathway known to interact with oxidative phosphorylation (OXPHOS). Reducing equivalents for OXPHOS are generated by 2 FAO steps. NADH, the substrate for the electron transport chain (ETC) complex I, is produced by the
long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) reaction of the mitochondrial trifunctional protein (TFP). The acyl-CoA dehydrogenases (ACADs) generate FADH2, which is funneled to QH2 of ETC complex III through the electron transfer flavoprotein dehydrogenase (ETFDH). The ETC is organized in
inner mitochondrial membrane supercomplexes (SC), which promote substrate channeling and catalytic efficiency. Therefore, in order for FAO to successfully produce ATP, it must rely on the successful transfer of NADH and QH2 to their corresponding complexes. We have previously demonstrated that FAO enzymes functionally and physically interact with the ETC-SC at two contact points: 1) TFP with the NADH-binding domain of ETC complex I; and 2) ETFDH with ETC complex III.

METHODS: SC activity was analyzed on the BN-PAGE using complex I and V in-gel activity stain. FAO protein interaction with SCs were measured with cross-link immunoprecipitation, MS, BN+2D+Western Blot, and bridging activity from FAO to ETC.

RESULTS/DISCUSSION: We examined explanted heart tissue from 18 heart transplant patients with no known genetic or metabolic diagnosis, and found that 80% lacked SC, implicating energy deficit as an important end point in cardiac disease. FAO protein interaction with SCs was also compromised. Mouse models of various FAO deficiencies also demonstrated a dramatic reduction in ETC SCs, further impairing bioenergetics through reduced ETC function. Together, these results further demonstrate the clinical importance of the linkage between FAO and ETC and emphasize the importance of an integrated molecular architecture for the major energy generating pathways.

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