Mutation and functional analysis of ABCC 2/multidrug resistance protein 2 in a J apanese patient with D ubin– J ohnson syndrome

D ubin– J ohnson syndrome ( DJS ) is a recessive inherited disorder characterized by conjugated hyperbilirubinemia. It is caused by dysfunction of adenosine triphosphate‐binding cassette, sub‐family C , member 2 ( ABCC 2/ MRP 2) on the canalicular membrane of hepatocytes. We performed mutational analysis of the ABCC 2 / MRP 2 gene in a J apanese female with DJS . Furthermore, we investigated the effects of the two identified DJS ‐associated mutations on MRP 2 function. We found a compound heterozygous mutation in the patient: W709R (c.2124T> C ), a missense mutation in exon 17, and R1310X (c.3928C> T ), a nonsense mutation in exon 28. DJS ‐associated mutations have been shown to impair the protein maturation and transport activity of ABCC 2/ MRP 2. We established HEK 293 cell lines stably expressing one of the two identified DJS ‐associated mutations. Expressed W709R MRP 2 was mainly core‐glycosylated, predominantly retained in the endoplasmic reticulum, and exhibited no transport activity, suggesting that this mutation causes deficient maturation and impaired protein sorting. No MRP 2 protein was expressed from HEK 293 cells transfected with an R1310X ‐containing construct. This compound heterozygous mutation of the MRP 2 gene causes dysfunction of the MRP 2 protein and the hyperbilirubinemia seen in DJS .