# Hepatic degradation of cytochrome P450 enzymes

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA, SAN FRANCISCO · 2022 · $452,200

## Abstract

PROJECT SUMMARY/ABSTRACT:
The hepatic endoplasmic reticulum (ER)-anchored monotopic proteins, cytochromes P450 (P450s) are
enzymes that metabolize endo- and xenobiotics i.e. drugs, carcinogens, toxins, natural and chemical products.
These agents modulate liver P450 content via increased formation or loss via inactivation and/or proteolytic
degradation, resulting in clinically significant drug-drug interactions (DDIs). DDIs often stem from altered P450
ER-associated degradation (ERAD) elicited by drug-mediated P450 stabilization i.e. ethanol (EtOH), or
enhanced drug-mediated P450 degradation (i.e. grapefruit juice). Hepatic P450 ERAD involves two major
pathways: Ubiquitin (Ub)-dependent proteasomal degradation (UPD) and autophagic-lysosomal degradation
(ALD). Some P450s (CYP3A4, the major human liver/intestinal P450) incur UPD, others (CYP2B1) incur ALD
and yet others (EtOH-metabolizing CYP2E1) incur both. The determinants of this differential P450 proteolytic
sorting are unknown and their identification are major goals of our future research. Plausible determinants
include (i) P450-homomerization in the ER-membrane; (ii) localization in lipid-disordered (ld) versus lipid-
ordered (lo; lipid rafts) ER-microdomains, resistant to detergent extraction (DRMs); (iii) propensity for ER or
cytoplasmic P450 aggregation and subsequent recruitment by the autophagic receptors p62/Sequestosome
and NBR-1 (neighbor of Braca 1 gene); (iv) specific post-translational modifications other than ubiquitination
(i.e. phosphorylation, acetylation); and (v) specific structural domains that confer differential sorting into ALD
versus UPD to two closely related orthologous or isoformic P450s. We propose to employ various experimental
approaches such as: Confocal fluorescence microscopy, bimolecular fluorescence complementation,
fluorescence resonance energy transfer (FRET), in-cell chemical crosslinking, rigorous affinity
immunopurification (AIP) with alpaca nanobodies, proteomic (LC-MS/MS) analyses, LC-MS/MS analyses of
protein interactions and interactant identification through proximity labeling, as well as post-translational
modifications, p62-/NBR-1-deletion mutants and gene ablated cells, P450-chimeras and fusion proteins, and
relevant genetic (ATG5-/-, p62-/-, NBR-1-/-) mouse models primary cultured rat and human hepatocytes and cell
lines. Elucidation of these fundamental aspects of P450 ERAD processes, we believe, are important because
they would not only advance our understanding of basic P450 biology/physiology, but also critically impact on
P450-dependent therapeutics and pathophysiology, and thus are clinically relevant. Understanding the
molecular determinants of P450 levels is critical for precision dosing of P450 drug substrates and for
unraveling the role of endogenous P450 substrates in physiology and pathophysiology. We believe the insights
gained from these studies will be universally applicable to other cellular proteins.

## Key facts

- **NIH application ID:** 10400896
- **Project number:** 5R01GM044037-28
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
- **Principal Investigator:** Maria Almira Correia
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $452,200
- **Award type:** 5
- **Project period:** 1990-04-01 → 2024-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10400896

## Citation

> US National Institutes of Health, RePORTER application 10400896, Hepatic degradation of cytochrome P450 enzymes (5R01GM044037-28). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10400896. Licensed CC0.

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