Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It is well known that transporter proteins play a key role in governing drug absorption, distribution, and elimination in the body, and, accordingly, they are now considered as causes of drug-drug interactions and interindividual differences in pharmacokinetic profiles. Polarized tissues directly involved in drug disposition (intestine, kidney, and liver) and restricted distribution to naive sanctuaries (blood-tissue barriers) asymmetrically express a variety of drug transporters on the apical and basolateral sides, resulting in vectorial drug transport. For example, the organic anion transporting polypeptide (OATP) family on the sinusoidal (basolateral) membrane and multidrug resistance-associated protein 2 (MRP2/ABCC2) on the apical bile canalicular membrane of hepatocytes take up and excrete organic anionic compounds from blood to bile. Such vectorial transcellular transport is fundamentally attributable to the asymmetrical distribution of transporter molecules in polarized cells. Besides the apical/basolateral sorting direction, distribution of the transporter protein between the membrane surface (active site) and the intracellular fraction (inactive site) is of practical importance for the quantitative evaluation of drug transport processes. The most characterized drug transporter associated with this issue is MRP2 on the hepatocyte canalicular (apical) membrane, and it is linked to a genetic disease. Dubin-Johnson syndrome is sometimes caused by impaired canalicular surface expression of MRP2 by a single amino acid substitution. Moreover, single nucleotide polymorphisms in OATP-C/SLC21A6 (SLCO1B1) also affect membrane surface expression, and actually lead to the altered pharmacokinetic profile of pravastatin in healthy subjects. In this review article, the asymmetrical transporter distribution and altered surface expression in polarized tissues are discussed.
 ...
PMID:Apical/basolateral surface expression of drug transporters and its role in vectorial drug transport. 1618 Jan 15

Direct hyperbilirubinemia, may result from a variety of pathologies, including structural obstructions with biliary tract occlusions (as in cholelithiasis), infections (e.g. hepatitis) and genetic disorders (Rotor's and Dubin-Johnson's syndrome). One of the less common and probably more frequently underdiagnosed causes is benign recurrent intrahepatic cholestasis (BRIC). First described in 1959, BRIC was further classified into two subgroups which differ in their pathogenesis and clinical manifestation. Both BRIC types originate from impaired function bile salt excretion from hepatocytes to the canaliculi which is mediated by the bile salt export pump (BSEP) which is located on the hepatyocyte membrane, unevenly distributed within the membrane lipid bilayer. In BRIC type-I, a mutation impairs the asymmetrical distribution of BSEP. In BRIC type-II, a mutation occurs directly damaging the BSEP. Apart from cholestasis, clinical manifestations of BRIC type-I include extra-hepatic symptoms such as watery diarrhea, pancreatitis and hearing impairment. Patients with BRIC type-II present mainly with hepatobiliary disease such as colelithiasis. In the past, BRIC was conventionally considered to result in no more than canalicular cholestasis, however several reports have associated BRIC with fibrosis and porto-portal septa formation. Disease course may last between weeks and months, more common in females, at any age, and usually resolves spontaneously, although chronic liver disease has also been described. Treatment modalities range from expectant management, medication (cholestyramine, ursolit) or even surgery (biliary bypass/liver transplantation). This report describes a patient with BRIC type-II and reviews the relevant literature.
 ...
PMID:[Benign recurrent intrahepatic cholestasis type-II--a rare cause of direct hyperbilirubinemia exacerbations with hepatic fibrosis]. 1877 Sep 56