Abstract
In the renal proximal tubule, organic anion transporters (OATs) mediate the removal of endogenous and exogenous toxins from blood for excretion in urine. OATs at the basolateral membrane drive organic anions into the cells, through exchange for dicarboxylates. At the apical membrane, different transporters deliver organic anions to the lumen. hOAT4 resides in the apical membrane, but its role in transport is unclear. Here we describe a new expression system to characterize hOAT4 and other OATs. An insect cell line (Sf9) was infected with Baculovirus containing hOAT4 cDNA under the control of the polyhedrin promoter. Although ABC transporters have been expressed using Baculovirus, this is the first report of insect cell expression of any OAT. Membrane vesicles from infected Sf9 cells transported known hOAT4 substrates (DHEAs, MTX and OTA) in a time-dependent manner. hOAT4-specific accumulation was inhibited by probenecid and increased when vesicles were preloaded with glutarate, suggesting organic anion exchange. In summary, Baculovirus-expressed hOAT4 is functionally consistent with protein from other systems. Isolated membrane vesicles derived from Baculovirus-infected Sf9 cells can therefore be used to characterize the mechanisms by which OATs function. This research was supported by the Intramural Research Program of the NIH, NIEHS.
Published Version
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