Calnexin depletion by ER-stress during cholestasis inhibits the Na+-taurocholate Cotransporting Polypeptide (NTCP)

ABSTRACT: Impaired bile flow (cholestasis) leads to transcriptional downregulation of the bile acid importer Na+-taurocholate co-transporting protein (NTCP) and to ER-stress in the liver. Here, we show that ER-stress induction strongly reduces NTCP protein expression, plasma membrane abundance and NTCP-mediated bile acid uptake. This is not controlled via a single specific UPR-pathway but mainly depends on the interaction of NTCP with calnexin, an ER chaperone involved in folding of N-glycosylated proteins. In mice, expression of both Ntcp and calnexin was reduced by thapsigargin-induced ER-stress. Calnexin downregulation in HepG2 and U2OS cells results in a decreased NTCP expression and a reduced bile acid uptake. Calreticulin shows partial functional redundancy with calnexin as it also interacts with NTCP, and is downregulated upon ER-stress, but specifically in calnexin-depleted cells. In conclusion, ER stress-induced downregulation of calnexin provides an additional mechanism to dampen NTCP-mediated bile acid uptake during cholestasis.

INSTRUMENT(S):

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Hepatocyte, Liver

DISEASE(S): Cholestasis

SUBMITTER: Harmjan Vos  

LAB HEAD: Stan F.J van de Graaf

PROVIDER: PXD007948 | Pride | 2019-01-07

REPOSITORIES: Pride