Bile Salt Export Pump (BSEP/ABCB11): Trafficking and Sorting Disturbances
Hisamitsu Hayashi and Yuichi Sugiyama
Affiliation: Laboratory of Molecular Pharmacokinetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Bile salt export pump (BSEP/ABCB11), a member of the family of ATP-binding cassette transporters, is localized
on the canalicular membrane of hepatocytes and mediates the efficient biliary excretion of bile acid. The secretion of
bile acid into bile by BSEP provides the primary osmotic driving force for bile flow generation. Intrahepatic cholestasis
resulting from dysfunction of BSEP can be caused by a mutation in the gene encoding this protein or by acquired factors,
such as the side effects of xenobiotics and drugs. In some pathophysiological states, inhibition of BSEP function is associated
with its reduced expression on the canalicular membrane caused by impaired trafficking and sorting of BSEP. This
fact has generated interest in better understanding the trafficking and sorting mechanism of BSEP. This review describes
the molecular characteristics and physiological roles of BSEP, the trafficking and sorting machinery of BSEP, and the
mechanisms responsible for disturbance of BSEP, which causes intrahepatic cholestasis.
Keywords: ATP-binding cassette (ABC) transporters, bile acid, bile formation, Bile Salt Export Pump (BSEP), cholestasis,
protein trafficking, protein degradation.
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