Hepatic palmitoyl-proteomes and acyl-protein thioesterase protein proximity networks link lipid modification and mitochondria

ABSTRACT: Elevated fatty acids are associated with insulin resistance. Fatty acids can reversibly modify proteins through a process known as S-palmitoylation. To test the hypothesis that depalmitoylation by acyl-protein thioesterases 1 and 2 (APT1 and APT2) in the liver regulates glucose metabolism, we generated liver-specific APT1 and/or APT2 knockout mice, fed them a high-fat diet (HFD), and then used acyl resin-assisted capture to isolate palmitoylated proteins from APT KO livers. We found that APT1 predominates over APT2 in the liver, primarily depalmitoylating mitochondrial proteins, including several proteins linked to glutamine metabolism. To corroborate these APT1 and APT2 substrates and identify other APT regulators, we determined the protein-protein proximity network of APT1 and APT2 by fusing each enzyme to the biotin ligase miniTurbo (mT). Expression of these APT-mT constructs in HepG2 cells, followed by purification of biotin-labeled proteins and mass spectrometry, revealed APT proximity networks encompassing mitochondrial proteins including the major translocases Tomm20 and Timm44. APT1 also interacted with Slc1a5 (ASCT2), the only glutamine transporter known to localize to mitochondria. HFD-fed male mice with dual but not single deletion of APT1 and APT2 from the liver had insulin resistance and fasting hyperglycemia. Elevated fasting glucose was also associated with increased glutamine-driven gluconeogenesis and decreased liver mass. These data suggest that APT1 and APT2 regulate hepatic glucose metabolism and insulin signaling in a functionally redundant manner. The identification of hepatic depalmitoylation substrates and protein-protein proximity networks for APT1 and APT2 establishes a framework for defining mechanisms underlying metabolic disease.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Liver

SUBMITTER: Qiang Zhang  

LAB HEAD: Clay Semenkovich

PROVIDER: PXD041552 | Pride | 2023-11-05

REPOSITORIES: Pride