Deficiency of glycerol-3-phosphate acyltransferase 1 decreases triacylglycerol storage and induces fatty acid oxidation in insect fat body

Glycerol-3-phosphate acyltransferases (GPAT) catalyze the initial and rate-limiting step for the de novo synthesis of triacylglycerol (TAG). Four mammalian GPAT isoforms have been identified: the mitochondria-associated GPAT1 and 2, and the endoplasmic reticulum (ER)-associated GPAT3 and 4. In the insect Rhodnius prolixus, a vector of Chagas' disease, we previously predicted a mitochondrial-like isoform (RhoprGPAT1) from genomic data. In the current study, we clone the RhoprGPAT1 coding sequence and identify an ER-associated GPAT (RhoprGPAT4) as the second isoform in the insect. RhoprGPAT1 contributes 15% of the total GPAT activity in anterior midgut, 50% in posterior midgut and fat body, and 70% in the ovary. The RhoprGpat1 gene is the predominant transcript in the midgut and fat body. To evaluate the physiological relevance of RhoprGPAT1, we generate RhoprGPAT1-deficient insects. The knockdown of RhoprGpat1 results in 50% and 65% decrease in TAG content in the posterior midgut and fat body, respectively. RhoprGpat1-deficient insects also exhibits impaired lipid droplet expansion and a 2-fold increase in fatty acid β-oxidation rates in the fat body. We propose that the RhoprGPAT1 mitochondrial-like isoform is required to channel fatty acyl chains towards TAG synthesis and away from β-oxidation. Such a process is crucial for the insect lipid homeostasis. •Two GPAT genes were cloned and shown to be independently regulated.•GPAT activities varied between organs.•GPAT1 was required for TAG accumulation in the midgut and fat body.•GPAT1 knockdown induced the oxidation of fatty acids.