RT Journal Article
SR Electronic
T1 Vesicular Transport of Newly Synthesized Cytochromes P4501A to the Outside of Rat Hepatocyte Plasma Membranes
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 1063
OP 1069
VO 294
IS 3
A1 Marie-Anne Robin
A1 Véronique Descatoire
A1 Marie Le Roy
A1 Alain Berson
A1 François-Pierre Lebreton
A1 Michel Maratrat
A1 François Ballet
A1 Jacqueline Loeper
A1 Dominique Pessayre
YR 2000
UL http://jpet.aspetjournals.org/content/294/3/1063.abstract
AB Anti-cytochrome P450 (CYP)1A2 autoantibodies are found in dihydralazine-induced hepatitis, and CYPs2B and 2C have been shown to follow vesicular flow to the plasma membrane (PM). However, it is unknown whether other CYPs follow this route, whether NADPH-CYP reductase is present on the hepatocyte surface, and whether autoimmune hepatitis-inducing drugs increase PM CYPs. In this study, we determined the transmembrane topology and transport of CYPs1A in rat hepatocytes. In cultured hepatocytes, colchicine and other vesicular transport inhibitors decreased PM CYPs1A assessed by flow cytometry. Colchicine administration also decreased PM CYPs1A in vivo. Pulse chase experiments with [35S]methionine showed that only the newly synthesized CYP molecules are transferred to the PM, whereas microsomal CYP1A2 was stably radiolabeled for several hours. In contrast, radiolabeled CYP1A2 reached the PM and disappeared from the PM with half-lives of less than 30 min. Confocal microscopy, biotinylation, and coimmunoprecipitation experiments showed that PM CYPs1A and CYP reductase are present on the cell surface, and that the reductase is closely associated with PM CYPs. Exposure of whole cells to an anti-CYP1A1/2 antibody at 4°C, before five washes and PM preparation, abolished PM CYPs1A-supported monooxygenase activity, indicating that PM CYPs are mostly located on the external surface. Dihydralazine and other CYPs1A inducers increased PM CYPs1A. In conclusion, newly synthesized CYPs1A follow vesicular flow to the outside of the PM, and NADPH-CYP reductase also is located on the hepatocyte surface. Dihydralazine administration increases PM CYP1A2, its autoimmune target. The American Society for Pharmacology and Experimental Therapeutics