Bile acids have been recognized to function as second messengers and hormones, with clinical implications in glucose, lipid and energy metabolism. The human apical sodium- dependent bile acid transporter (hASBT) plays a key role in the enterohepatic recycling of bile salts, cholesterol homeostasis, and serves as a molecular target for hypercholesterolemic agents and pharmaceutical prodrug strategies. Despite its clinical significance, ASBT is poorly characterized at the molecular level. The proposed research will focus on the structural biology of ASBT. Two recent bacterial crystal structures claim evolutionary relatedness to hASBT, yet their topology is in clear contrast to biochemical data in the literature. The current proposal directly confronts this controversy and our plan to advance understanding of bile acid transporter structure, function and regulation is organized around the following aims: 1) Do bacterial transporter structures provide representative structural models for eukaryotic SLC10 orthologs? wherein we hypothesize that analysis of genetic ancestry and substrate phenotype of orthologs can determine evolutionary and structural relatedness of (putative) prokaryotic and eukaryotic SLC10A family members; further, we aim to express, purify, crystallize and determine the x-ray structure of eukaryotic SLC10A orthologs; 2) To characterize and map the functional regulation and modulation of hASBT expression; where we will apply a proteomics approach to determining post- translational modifications temporally. Based on our preliminary data we will further investigate the organization of hASBT in higher-order dimers or multimers as a way of controlling function. Information gained by these studies will significantly increase our understanding of the structural interactions that drive bile acid transport and further our structural knowledge of solute carrier (SLC) proteins in general. Additionally, it may aid future development of specific therapeutic strategies against hypercholesterolemia and related cardiovascular and metabolic diseases.

Public Health Relevance

Bile acids play an invaluable role in the intestinal absorption of food-derived lipids and lipid-soluble vitamins and drugs. The human bile acid pool is efficiently conserved through recirculation by bile acid transporters in the intestine and the liver. Fecal loss of bile acids is compensated by synthesis in the liver from its precursor, cholesterol; thus, bile acid transporters play an intricate role in blood cholesterol levels and they may be used as a target for cholesterol-lowering drugs. The studies in this proposal aim to determine the structure and regulation of a key intestinal bile acid transporter, ASBT. When completed, these studies will provide critical information for designing new therapeutics aimed at this transport system.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK061425-13
Application #
9517005
Study Section
Xenobiotic and Nutrient Disposition and Action Study Section (XNDA)
Program Officer
Burgess-Beusse, Bonnie L
Project Start
2003-05-01
Project End
2021-06-30
Budget Start
2018-07-01
Budget End
2019-06-30
Support Year
13
Fiscal Year
2018
Total Cost
Indirect Cost
Name
University of Maryland Baltimore
Department
Pharmacology
Type
Schools of Pharmacy
DUNS #
188435911
City
Baltimore
State
MD
Country
United States
Zip Code
21201
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Czuba, Lindsay C; Hillgren, Kathleen M; Swaan, Peter W (2018) Post-translational modifications of transporters. Pharmacol Ther 192:88-99
Shiffka, Stephanie J; Kane, Maureen A; Swaan, Peter W (2017) Planar bile acids in health and disease. Biochim Biophys Acta Biomembr 1859:2269-2276
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Lynch, Caitlin; Pan, Yongmei; Li, Linhao et al. (2014) Activation of the constitutive androstane receptor inhibits gluconeogenesis without affecting lipogenesis or fatty acid synthesis in human hepatocytes. Toxicol Appl Pharmacol 279:33-42
Moore, Robyn H; Chothe, Paresh; Swaan, Peter W (2013) Transmembrane domain V plays a stabilizing role in the function of human bile acid transporter SLC10A2. Biochemistry 52:5117-24
Lynch, Caitlin; Pan, Yongmei; Li, Linhao et al. (2013) Identification of novel activators of constitutive androstane receptor from FDA-approved drugs by integrated computational and biological approaches. Pharm Res 30:489-501
Sabit, Hairat; Mallajosyula, Sairam S; MacKerell Jr, Alexander D et al. (2013) Transmembrane domain II of the human bile acid transporter SLC10A2 coordinates sodium translocation. J Biol Chem 288:32394-404
Claro da Silva, Tatiana; Polli, James E; Swaan, Peter W (2013) The solute carrier family 10 (SLC10): beyond bile acid transport. Mol Aspects Med 34:252-69
González, Pablo M; Hussainzada, Naissan; Swaan, Peter W et al. (2012) Putative irreversible inhibitors of the human sodium-dependent bile acid transporter (hASBT; SLC10A2) support the role of transmembrane domain 7 in substrate binding/translocation. Pharm Res 29:1821-31

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