Pharmaceutical Sciences Faculty Publications

Title

The Heavy Metal Cadmium Induces Valosin-Containing Protein (VCP)-Mediated Aggresome Formation

Document Type

Article

Publication Date

5-1-2008

Journal Title

Toxicology and Applied Pharmacology

ISSN

0041-008X

Volume

228

Issue

3

First Page

351

Last Page

363

DOI

10.1016/j.taap.2007.12.026

PubMed ID

18261755

PubMed Central® ID

PMC2692476

Abstract

Cadmium (Cd2+) is a heavy metal ion known to have a long biological half-life in humans. Accumulating evidence shows that exposure to Cd2+ is associated with neurodegenerative diseases characterized by the retention of ubiquitinated and misfolded proteins in the lesions. Here, we report that Cd2+ directly induces the formation of protein inclusion bodies in cells. The protein inclusion body is an aggresome, a major organelle for collecting ubiquitinated or misfolded proteins. Our results show that aggresomes are enriched in the detergent-insoluble fraction of Cd2+-treated cell lysates. Proteomic analysis identified 145 proteins in the aggresome-enriched fractions. One of the proteins is the highly conserved valosin-containing protein (VCP), which has been shown to colocalize with aggresomes and bind ubiquitinated proteins through its N domain (#1-200). Our subsequent examination of VCP's role in the formation of aggresomes induced by Cd2+ indicates that the C-terminal tail (#780-806) of VCP interacts with histone deacetylase HDAC6, a mediator for aggresome formation, suggesting that VCP participates in transporting ubiquitinated proteins to aggresomes. This function of VCP is impaired by inhibition of the deacetylase activity of HDAC6 or by over-expression of VCP mutants that do not bind ubiquitinated proteins or HDAC6. Our results indicate that Cd2+ induces the formation of protein inclusion bodies by promoting the accumulation of ubiquitinated proteins in aggresomes through VCP and HDAC6. Our delineation of the role of VCP in regulating cell responses to ubiquitinated proteins has important implications for understanding Cd2+ toxicity and associated diseases.

Keywords

Adenosine triphosphatases, cadmium, cell cycle proteins, cells, cultured, histone deacetylases, humans, inclusion bodies, mass spectrometry, protein folding, protein structure, tertiary, ubiquitin, valosin containing protein

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