Proteasome inhibition compromises direct retention of cytochrome P450 2C2 in the endoplasmic reticulum

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Elzbieta Szczesna-Skorupa1, Byron Kemper

  • 1Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.

Experimental Cell Research
|August 30, 2008
PubMed

Insights

Proteasomal inhibitors affect endoplasmic reticulum (ER) protein retention. Inhibition increases expression of some cytochrome P450 chimeras and causes their redistribution, suggesting protein degradation influences ER localization.

Area of Science:

  • Biochemistry
  • Cell Biology
  • Molecular Biology

Background:

  • Endoplasmic reticulum (ER) protein retention is crucial for cellular function.
  • Cytochromes P450 (CYPs) are important drug-metabolizing enzymes whose ER localization is not fully understood.
  • Protein degradation pathways, including the proteasome, are implicated in protein quality control.

Purpose of the Study:

  • To investigate the role of protein degradation in the ER retention of cytochromes P450.
  • To examine the effects of proteasomal inhibitors on the expression and localization of CYP2C2 and related proteins.

Main Methods:

  • Transfection of cells with green fluorescent protein (GFP) chimeras of CYP2C2 and related proteins.
  • Treatment with proteasomal inhibitors and microtubular inhibitor (nocodazole).
  • Analysis of protein expression levels and cellular distribution using microscopy.

Main Results:

  • Proteasomal inhibition increased expression of full-length CYP2C2 and its cytosolic domain chimeras.
  • All examined CYP chimeras, BAP31, CYP2E1, CYP3A4, and P450 reductase redistributed from the ER to a perinuclear compartment and sometimes the cell surface.
  • Redistribution was blocked by nocodazole, indicating involvement of vesicular transport, and did not result from ER retention receptor saturation.

Conclusions:

  • Protein degradation pathways, particularly proteasomal degradation, play a role in the ER retention of cytochromes P450.
  • Proteasomal inhibition can alter ER protein localization, potentially by affecting key retention proteins or ER membrane composition.

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