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Arch Biochem Biophys. 2009 Mar 1;483(1):66-74. doi: 10.1016/j.abb.2008.12.001. Epub 2008 Dec 10.

CYP3A4 ubiquitination by gp78 (the tumor autocrine motility factor receptor, AMFR) and CHIP E3 ligases.

Author information

1
Department of Cellular and Molecular Pharmacology, University of California San Francisco, 94158-2280, United States.

Abstract

Human liver CYP3A4 is an endoplasmic reticulum (ER)-anchored hemoprotein responsible for the metabolism of >50% of clinically prescribed drugs. After heterologous expression in Saccharomyces cerevisiae, it is degraded via the ubiquitin (Ub)-dependent 26S proteasomal pathway that utilizes Ubc7p/Cue1p, but none of the canonical Ub-ligases (E3s) Hrd1p/Hrd3p, Doa10p, and Rsp5p involved in ER-associated degradation (ERAD). To identify an Ub-ligase capable of ubiquitinating CYP3A4, we examined various in vitro reconstituted mammalian E3 systems, using purified and functionally characterized recombinant components. Of these, the cytosolic domain of the ER-protein gp78, also known as the tumor autocrine motility factor receptor (AMFR), an UBC7-dependent polytopic RING-finger E3, effectively ubiquitinated CYP3A4 in vitro, as did the UbcH5a-dependent cytosolic E3 CHIP. CYP3A4 immunoprecipitation coupled with anti-Ub immunoblotting analyses confirmed its ubiquitination in these reconstituted systems. Thus, both UBC7/gp78 and UbcH5a/CHIP may be involved in CYP3A4 ERAD, although their relative physiological contribution remains to be established.

PMID:
19103148
PMCID:
PMC2881844
DOI:
10.1016/j.abb.2008.12.001
[Indexed for MEDLINE]
Free PMC Article

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