Sustained internalization of the hepatocanalicular transporter multidrug resistance-associated protein 2 (Mrp2) in cholestasis leads to its exacerbated proteosomal degradation

MEDEOT ANABELA CAROLINA; ANDERMATTEN ROMINA BELEN; SALAS GIMENA; SCHUCK VIRGINIA SOLEDAD; BAROSSO ISMAEL RICARDO; CROCENZI FERNANDO ARIEL; ROMA MARCELO GABRIEL

MAr del Plata

Congreso; Reunión conjunta SAFIS-SAI-SAIC; 2022

SAIC-SAFIS-SAI

Exacerbated endocytosis of canalicular carriers, including Mrp2, is a main mechanism involved in cholestasis, as has been shown with the model cholestatic agent, taurolithocholate (TLC) (Crocenzi et al. Gut 52: 1170, 2003). We hypothesized that this exacerbated internalization is followed by accelerated degradation, thus explaining the unchanged carrier protein expression despite increased synthesis observed in chronic cholestatic diseases. We therefore tested here whether sustained Mrp2 internalization leads to accelerated degradation, and if so, which degradation mechanism is involved. Mrp2 protein expression was quantified by Western blot in sandwich-cultured rat hepatocytes (SCRH) incubated with TLC (2.5 µM), or vehicle (DMSO) in controls (C), in the presence of cycloheximide to block “de novo” Mrp2 synthesis. TLC exposure for 12 hs induced no change in Mrp2 expression as compared to C, whereas a significant decrease was observed at 24 h (69±4%; n=7) and 48 h (66±8%; n=3); p