View Program - 63rd Annual Drosophila Research Conference

De novo lipogenesis (DNL) is tightly regulated during animal growth and development. It is well known that under conditions like excess nutrition, obesity, and cancer, DNL is activated through transcriptional regulation of lipogenic genes, including fatty acid synthase (FASN). Surprisingly, we show that the levels of FASN protein remain unchanged during Drosophila larval development, while its acetylation increases in fast-growing larvae and is positively correlated to the FASN enzymatic activity. This finding suggests that the regulation of FASN activity and developmental DNL is not at the transcription and translation steps; rather, it is regulated through post-translational modifications (PTMs), especially lysine acetylation. Through mass-spectrometry analysis, we identified two evolutionarily conserved lysine residues that are acetylated in both fly and human FASN proteins. One of them, K813 in fly, is located nearby the active site of the malonyl/acetyltransferase (MAT) domain. Acetylation of K813 is predicted to enlarge the binding pocket of MAT domain to allow fast substrate loading. Indeed, flies with lysine to arginine substitution (K813R, acetylation deficiency mutants) show decreased lipogenesis and FASN activity, reduced body weight, and delayed pupariation. To further understand how acetylation of lysine residue K813 is regulated, we screen all major lysine acetyltransferases (KATs) and deacetylases (KDACs and Sirtuins). We identified deacetylase Sirt1 as the key negative regulator of FASN acetylation. However, none of the KATs that we examined seems to play a role in promoting the acetylation of K813. Intriguingly, our genetics and biochemical studies show that acetylation of lysine residue K813 does not require the participation of KATs, while it is mediated by acetyl-CoA levels. Through site-specific mutagenesis, we identified three residues downstream of K813 that consist of a new functional motif (R/Q-xx-G-x-G/A) of FASN, which is responsible for acetyl-CoA recognition and binding. Mutations of these residues block the autoacetylation of K813 in vitro. Taken together, our results uncover a novel regulation in metabolic homeostasis. It is suggested that the site-specific autoacetylation at lysine residue K813 is crucial in sensing the fluctuated fuels (acetyl-CoA) and fine-tuning FASN enzymatic activity. Thus, our findings discover a novel self-regulatory module that links signaling metabolite acetyl-CoA, lysine acetylation, and DNL.

Acetyl-CoA mediated autoacetylation of fatty acid synthase as a metabolic switch for de novo lipogenesis in developing Drosophila