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Palmitoylation of ketogenic enzyme HMGCS2 enhances its interaction with PPARalpha and transcription at the Hmgcs2 PPRE.

ABSTRACT: Excessive liver production of ketone bodies is one of many metabolic complications that can arise from diabetes, and in severe untreated cases, it can result in ketoacidosis, coma, and death. Mitochondrial HMG-CoA synthase (HMGCS2), the rate-limiting enzyme in ketogenesis, has been shown to interact with PPARalpha and act as a coactivator to up-regulate transcription from the PPRE of its own gene. Although protein palmitoylation is typically a cytosolic process that promotes membrane association, we recently identified 21 palmitoylated proteins in rat liver mitochondria, including HMGCS2. Herein, our data support a mechanism whereby palmitate is first added onto HMGCS2 active site Cys166 and then transacylated to Cys305. Palmitoylation promotes the HMGCS2/PPARalpha interaction, resulting in transcriptional activation from the Hmgcs2 PPRE. These results, together with the fact that 8 of the 21 palmitoylated mitochondrial proteins that we previously identified have nuclear receptor interacting motifs, demonstrate a novel--and perhaps ubiquitous--role for palmitoylation as a modulator of transcription.

SUBMITTER: Kostiuk MA

PROVIDER: S-EPMC2874477 | biostudies-other | 2010 Jun

REPOSITORIES: biostudies-other

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Palmitoylation of ketogenic enzyme HMGCS2 enhances its interaction with PPARalpha and transcription at the Hmgcs2 PPRE.

Kostiuk Morris A MA Keller Bernd O BO Berthiaume Luc G LG

FASEB journal : official publication of the Federation of American Societies for Experimental Biology 20100202 6

Excessive liver production of ketone bodies is one of many metabolic complications that can arise from diabetes, and in severe untreated cases, it can result in ketoacidosis, coma, and death. Mitochondrial HMG-CoA synthase (HMGCS2), the rate-limiting enzyme in ketogenesis, has been shown to interact with PPARalpha and act as a coactivator to up-regulate transcription from the PPRE of its own gene. Although protein palmitoylation is typically a cytosolic process that promotes membrane association ...[more]

PMID: 20124434

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Project description:Arabinogalactan proteins are abundant proteoglycans present on cell surfaces of plants and involved in many cellular processes, including somatic embryogenesis, cell-cell communication and cell elongation. Arabinogalactan proteins consist mainly of glycan, which is synthesized by post-translational modification of proteins in the secretory pathway. Importance of the variations in the glycan moiety of arabinogalactan proteins for their functions has been implicated, but its biosynthetic process is poorly understood.We have identified a novel enzyme in the biosynthesis of the glycan moiety of arabinogalactan proteins. The At1g08280 (AtGALT29A) from Arabidopsis thaliana encodes a putative glycosyltransferase (GT), which belongs to the Carbohydrate Active Enzyme family GT29. AtGALT29A co-expresses with other arabinogalactan GTs, AtGALT31A and AtGLCAT14A. The recombinant AtGALT29A expressed in Nicotiana benthamiana demonstrated a galactosyltransferase activity, transferring galactose from UDP-galactose to a mixture of various oligosaccharides derived from arabinogalactan proteins. The galactose-incorporated products were analyzed using structure-specific hydrolases indicating that the recombinant AtGALT29A possesses ?-1,6-galactosyltransferase activity, elongating ?-1,6-galactan side chains and forming 6-Gal branches on the ?-1,3-galactan main chain of arabinogalactan proteins. The fluorescence tagged AtGALT29A expressed in N. benthamiana was localized to Golgi stacks where it interacted with AtGALT31A as indicated by Förster resonance energy transfer. Biochemically, the enzyme complex containing AtGALT31A and AtGALT29A could be co-immunoprecipitated and the isolated protein complex exhibited increased level of ?-1,6-galactosyltransferase activities compared to AtGALT29A alone.AtGALT29A is a ?-1,6-galactosyltransferase and can interact with AtGALT31A. The complex can work cooperatively to enhance the activities of adding galactose residues 6-linked to ?-1,6-galactan and to ?-1,3-galactan. The results provide new knowledge of the glycosylation process of arabinogalactan proteins and the functional significance of protein-protein interactions among O-glycosylation enzymes.

Dataset Information

Palmitoylation of ketogenic enzyme HMGCS2 enhances its interaction with PPARalpha and transcription at the Hmgcs2 PPRE.

Publications

Palmitoylation of ketogenic enzyme HMGCS2 enhances its interaction with PPARalpha and transcription at the Hmgcs2 PPRE.

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