SARS-CoV-2 ORF7a Drives Mitochondrial Dysfunction via PDK4 Activation and Complex I Inhibition

Abstract

SARS-CoV-2 reprograms host metabolism to promote viral replication and evade immune responses. While infection is known to impair mitochondrial function and enhance glycolysis, the role of viral accessory proteins in these alterations remains unclear. Here, we investigate the metabolic impact of the accessory protein ORF7a. Lentiviral expression of ORF7a in human lung epithelial (A549) and monocytic (THP1) cells, coupled with integrated transcriptomic, proteomic, and metabolomic analyses, revealed profound dysregulation of glucose and lipid metabolism. ORF7a impaired oxidative phosphorylation, reducing basal and maximal respiration, inducing mitochondrial depolarization, and increasing reactive oxygen species. Mechanistically, ORF7a upregulated pyruvate dehydrogenase kinase 4 (PDK4), promoting pyruvate dehydrogenase (PDH) complex phosphorylation and suppressing pyruvate oxidation. However, pharmacological PDK4 inhibition did not restore respiration. High-resolution respirometry in frozen samples revealed impaired complex I function, while Blue Native-PAGE demonstrated defective respiratory supercomplex assembly. By linking enzymatic inhibition with structural destabilization, our study uncovers a functional vulnerability of the mitochondrial respiratory chain to viral manipulation. These findings establish ORF7a as a key modulator of host metabolic reprogramming and highlight mitochondrial pathways as potential therapeutic targets in COVID-19.