Abstract 1837: Tyr phosphorylation activates and inhibits upstream acetyltransferases and deacetylase of 6PGD, respectively, to promote cancer metabolism and tumor growth
Authors: Xia Siyuan , Shan Changliang , Fan Jun , Chen Jing 
Published: August 2019

Abstract
Background: We recently reported that 6-phosphogluconate dehydrogenase (6PGD), the third enzyme in the oxidative pentose phosphate pathway (PPP), is commonly activated by lysine acetylation in EGF-stimulated cells but “hijacked” in human cancer cells. Acetylation at K76 and K294 enhances 6PGD activation and is commonly observed in diverse human cancer cells, which is important for coordination of anabolic biosynthesis, redox homeostasis, and glycolysis in cells, providing an overall metabolic advantage to cancer cell proliferation and tumor growth. Moreover, we identified DLAT and ACAT2 as upstream acetyltransferases of K76 and K294, respectively, and HDAC4 as the deacetylase of both sites. However, it remains unclear how oncogenic signals regulate the activity of these acetyltransferases and deacetylase to control 6PGD activity and consequently contribute to tumor cell metabolism and tumor growth.
Methods: Tyrosine phosphorylation sites were identified in Mass Spec-based studies using recombinant purified ACAT2, DLAT and HDAC4 treated with active recombinant oncogenic tyrosine kinases in diverse in vitro kinase assays. Mutational analysis was performed to determine tyrosine phosphorylation sites that are crucial to activate ACAT2 and DLAT or inhibit HDAC4, and/or promote or attenuate 6PGD binding to ACAT2 and DLAT or HDAC4, respectively.
Results: We found that, although tyrosine phosphorylation does not affect 6PGD catalytic activity or binding to its upstream acetyltransferases and deacetylase, diverse growth factor receptors as well as oncogenic tyrosine kinases commonly phosphorylate ACAT2, DLAT and HDAC4, leading to catalytic activation of ACAT2 and DLAT but inhibition of HDAC4. Moreover, tyrosine phosphorylation promotes binding of 6PGD to ACAT2 and DLAT but attenuates HDAC4-6PGD association.
Conclusions: Our findings provide insight into the molecular mechanisms underlying 6PGD regulation, which responds to growth factor stimulation or oncogenic tyrosine kinases through activation and inhibition of upstream 6PGD acetyltransferases and deacetylase, respectively, via tyrosine phosphorylation. Moreover, our studies showcase the beauty of complex signal transduction-based regulation of cellular processes, where hierarchical, distinct posttranslational modifications act in concert to provide precise regulation of a series of sequential events to control catalytic activity of acetyltransferases ACAT2 and DLAT and deacetylase HDAC4 and kinetic formation of protein complex to regulate 6PGD in cancer cells, and subsequently contribute to cancer metabolism and tumor growth.
Note: This abstract was not presented at the meeting.
Citation Format: Siyuan Xia, Changliang Shan, Jun Fan, Jing Chen. Tyr phosphorylation activates and inhibits upstream acetyltransferases and deacetylase of 6PGD, respectively, to promote cancer metabolism and tumor growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1837.