Metta PinthongStefanie A G BlackFabiola M. RibeiroChumpol PholpramoolStephen S G FergusonRebecca Jane RylettWestern UniversityRobarts Research InstituteMahidol University2018-07-122018-07-122008-03-01Molecular Pharmacology. Vol.73, No.3 (2008), 801-812152101110026895X2-s2.0-40849083785https://repository.li.mahidol.ac.th/handle/20.500.14594/19879Excess formation of nitric oxide and superoxide by-products (peroxynitrite, reactive oxygen, and reactive nitrogen species) attenuates cholinergic transmission potentially having a role in Alzheimer disease pathogenesis. In this study, we investigated mechanisms by which acute exposure to peroxynitrite impairs function of the sodium-dependent hemicholinium-3 (HC-3)-sensitive choline transporter (CHT) that provides substrate for acetylcholine synthesis. The peroxynitrite generator 3-morpholinosydnonimine (SIN-1) acutely inhibited choline uptake in cells stably expressing FLAG-tagged rat CHT in a dose- and time-dependent manner, with an IC50 = 0.9 ± 0.14 mM and t 1/2 = 4 min. SIN-1 significantly reduced Vmax of choline uptake without altering the Km. This correlated with a SIN-1-induced decrease in cell surface CHT protein, observed as lowered levels of HC-3 binding and biotinylated CHT at the plasma membrane. It is noteworthy that short-term exposure of cells to SIN-1 accelerated the rate of internalization of CHT from the plasma membrane, but it did not alter return of CHT back to the cell surface. SIN-1 did not disrupt cell membrane integrity or cause cell death. Thus, the inhibitory effect of SIN-1 on choline uptake activity and HC-3 binding was related to enhanced internalization of CHT proteins from the plasma membrane to subcellular organelles. Copyright © 2008 The American Society for Pharmacology and Experimental Therapeutics.Mahidol UniversityPharmacology, Toxicology and PharmaceuticsArticleSCOPUS10.1124/mol.107.040881