Role of AIG1 and ADTRP in Endogenous FAHFA Regulation
Androgen‐induced gene 1 (AIG1) and Androgen‐dependent TFPI‐regulating protein (ADTRP) are atypical transmembrane hydrolases that rely on a catalytic threonine for their enzymatic activity. In vitro characterization of AIG1 and ADTRP in lysates and cells identified fatty acid ester of hydroxy fatty acids (FAHFAs) as their putative substrates. Here, we generate ADTRP knockout (Adtrp‐KO), AIG1 knockout (Aig1‐KO), and ADTRP/AIG1 double deficient (DKO) mice using CRISPR‐Cas9 technology to test whether these enzymes regulate FAHFAs in vivo. AIG1, ADTRP, or a deficiency in both enzymes leads to decreased FAHFA hydrolytic activity in tissue lysates. Quantitative measurement of FAHFA levels in several tissues revealed increased FAHFA levels in brown adipose tissue (BAT), subcutaneous adipose tissue (SQWAT), and perigonadal WAT (PGWAT) of Adtrp‐KO mice consistent with the loss of FAHFA degrading activity. Furthermore, contribution by AIG1 was modest and only observed in the kidney and BAT of DKO mice. Lipidomics of tissues from knockout and wild type control mice detected no significant changes in other lipid classes to indicate that these enzymes are specific for FAHFA substrates. Furthermore, we developed a potent and selective, dual AIG1/ADTRP inhibitor to enable pharmacological interrogation of these enzymes in vivo. Chemical inhibition of AIG1 and ADTRP raised FAHFA levels demonstrating acute regulation of FAHFAs. In aggregate, the results establish AIG1 and ADTRP as the only endogenous FAHFA hydrolases known, and describe resources (mice, inhibitors) needed to elucidate the biochemical and physiological role of these exciting enzymes.
Ertunc, Meric Erikci, Bernard P. Kok, William H. Parsons, et al. 2020. "Role of AIG1 and ADTRP in Endogenous FAHFA Regulation." FASEB Journal 34(S1).
Chemistry and Biochemistry
Conference abstract for the Annual Meeting on Experimental Biology, San Diego, CA, April 4-7, 2020.