Characterizing the Physiological and Pharmacological Roles of SLC22A24 Membrane transporters in the solute carrier superfamily (SLC) play critical roles in physiology and pharmacology serving in the cellular uptake and removal of endogenous metabolites and many prescription drugs. In spite of their importance, about one-fifth of SLC transporters have no known substrates and are considered “orphan” proteins. Recently, our laboratory de-orphaned one of these proteins, SLC22A24, by applying various methods, which included computational analyses of genomewide association signals, homology modeling, expression profiling, and importantly, isotopic uptake assays in cells stably expressing SLC22A24. Our studies revealed that SLC22A24 is an organic anion transporter with a preference for sulfate and glucuronide conjugates of steroids. Recent preliminary studies suggest that the transporter also plays an important role in drug disposition. The major goals of the proposed research are to determine the physiological and pharmacological roles of SLC22A24 in the disposition of steroid glucuronides and to discover other endogenous metabolites and pharmacologic agents that are substrates of SLC22A24. To achieve our goals, we have designed three specific aims. In aim 1, we will employ studies in cell lines to determine the localization of SLC22A24 to the basolateral or apical membranes. In addition, we will discover prescription drugs and other metabolites that are substrates of SLC22A24. In aim 2, we will use CRISPR/Cas9 methods to create transgenic mice expressing SLC22A24 in the proximal tubule and use the mice to determine its role in the disposition of pharmacologic and physiologic substrates of the transporter. Finally, in aim 3, we will conduct association studies in healthy volunteers to associate functional variants in SLC22A24 with plasma levels and renal clearance of steroid glucuronides. Methods employed will include confocal microscopy, isotopic uptake and flux assays in cells, CRISPR/Cas9 methods in mice, LC/MS/ metabolomic analytical methods, association analyses and clearance determinations in humans. We postulate that this comprehensive genomic, metabolomic and functional studies in cells, mice and in healthy volunteers including deep clinical phenotyping will serve as a blueprint for systematic evaluation of the physiological and pharmacological roles of a newly de-orphaned transporter.