Specialization
Biochemistry, metabolism, bioenergetics, apoptosis, cAMP signaling, development of enzymatic assay
Focus of research
Cyclic AMP is produced in mammalian cells by two different types of adenylyl cyclases: the canonical transmembrane adenylyl cyclases at the plasma membrane (tmACs, ADCY1~ADCY9) and the evolutionarily more conserved soluble adenylyl cyclase in the cytoplasm (sAC, ADCY10). While the tmACs are activated by stimulatory α-subunit of G-protein (Gαs) following activation of G-protein-coupled receptors, sAC has a basal activity that is maintained by local levels of bicarbonate, free Ca2+, and ATP. Despite their differences, sAC and tmACs share common cAMP effectors, such as protein kinase A (PKA), Epac1, and Eapc2.
My research focuses on the pathophysiologic role of the cAMP signlaing by the bicarbonate-sensing soluble adenylyl cyclase (sAC) (Chang & Oude Elferink. Front Physiol (2014):5;42). This research originates from my PhD research on the role of the long observed down-regulation of anion exchanger 2 (AE2, an important bicarbonate transporter for biliary bicarbonate secretion) in the pathogenesis of primary biliary cholangitis, an idiopathic inflammatory cholestatic cholangiopathy. Down-regulation of AE2 not only reduces bicarbonate secretion, but also leads to intracellular bicarbonate accumulation. I demonstrated that down-regulation of AE2 sensitized cholangiocytes to bile salt-induced apoptosis via the bicarboante-responsive sAC (Chang et al. Hepatology (2016);64, 522-534, Chang et al. Biochim Biophys Acta Mol Basis Dis (2018);1864:1232-1239). Since then, my research has further developed into understanding the regulation of metabolism by sAC and its application in various diseases:
(1) Regulation of cellualr bioenergetics by soluble adenylyl cyclase:
In this project, we study the acute metabolic regulation of soluble adenylyl cyclase with focus on glucose metabolism. Cellular bioenergetics is studied with Seahorse XF96e Analyzer for fluxes of proton (extracellular acidification rate, ECAR) and oxygen (oxygen consumption rate, OCR) in both intact cells and in digitonin-permeabilized cells (for mitochondrial electron transport chain). Results of ECAR is further validated by fluxes of gluocse, lactate, pyruvate, and glycogen, all assayed by an efficient, cost-effective workflow of in-house validated microplate assays (Gilglioni & Chang, et al. Hepatology Communications (2018):2;299-312). With the Peredox NADH/NAD+ biosensor, cytosolic NADH/NAD+ redox state is monitored real-time for comparison with ECAR and OCAR data from Seahorse. In addition, we also use phosphoproteomics, non-targeted metabolomics, and 13C-glucose fluxomics to elucidate the regulatory mechanism of sAC. (Funded by KWF)
(2) Role of soluble adenylyl cyclase in hepatic carcinogenesis:
The expression of soluble adenylyl cyclase has been shown to be down-regulated in multiple cancerous tissues as compared to adjacent normal tissues.We and others have demonstrated that suppression of sAC activity induces a Warburg-like metabolic phenotype. In this project, we study whether sAC plays a role in hepatic tumor formation in chronic cholestasis and in chemical-induced carcinogenesis in mice. (Funded by KWF)
(3) Regulation of macrophage functino and differentation by soluble adenylyl cyclase
Macrophages is an important player in the pathogenesis of various inflammatory diseases. Targeting cellular metabolism has emerged as a new way to modulate the immune functions of macrophages. Soluble adenylyl cyclase (sAC) is a conserved metabolic regulator of glycolysis and oxidative phosphorylation. In collacoration with the immunometabolism group of Dr. Jan Van den Bossche from the VUmc campus, we will jointly explore how targeting sAC can modulate macrophage functions in different contexts. Using both genetic model and pharmacological approach, we will comprehensively characterize how sAC regulates the metabolism and functions of primary macrophages by both functional assays and multi-layer omics. We aim to translate the result by exploring its therapeutic value in animal models of inflammatory diseases, such as inflammatory bowel disease. (Funded by AG&M)