The intracellular NPxY motif is critical in maintaining the function and expression of human organic anion transporting polypeptide 1B1

Publication date: Available online 7 April 2019Source: Biochimica et Biophysica Acta (BBA) - BiomembranesAuthor(s): Xuyang Wang, Yushuang Liang, Zihui Fang, Jiujiu Huang, Mei HongAbstractOrganic anion transporting polypeptides (OATPs, gene symbol SLCO) mediate sodium-independent transport of endogenous compounds such as bile salts, hormones and their conjugates as well as toxins and drugs. OATP1B1 is the major OATP specifically expressed at the basolateral membrane of human hepatocytes and many clinically important drugs have been shown to be substrates of the transporter. According to the computer-based hydropathy analysis, a large intracellular loop 3 (IL3) is situated between transmembrane domain 6 and 7 of OATPs, in which a conserved NPxY motif is found. In the current study, HEK293 cells expressing the HA-tagged OATP1B1 was utilized to investigate the role of the NPxY motif for the function and expression of the transporter. Alanine replacement of N335 or P336 retained substantial uptake function; while simultaneous mutation of these residues resulted in a double mutant that lost almost all the transport activity. On the other hand, Y338A showed>80% reduction for estrone-3-sulfate uptake. Plasma membrane protein analysis revealed that N335/P336A completely lost its cell surface protein expression; while that of Y338A is dramatically reduced. Further investigation with pharmacological inhibitors and immunocytochemistry demonstrated that N335/336A is detained in the Golgi ...
Source: Biochimica et Biophysica Acta (BBA) Biomembranes - Category: Biochemistry Source Type: research