Human CHCHD4 mitochondrial proteins regulate cellular oxygen consumption rate and metabolism and provide a critical role in hypoxia signaling and tumor progression
Jun Yang, … , Adrian L. Harris, Margaret Ashcroft
Jun Yang, … , Adrian L. Harris, Margaret Ashcroft
Published February 1, 2012; First published January 3, 2012
Citation Information: J Clin Invest. 2012;122(2):600-611. https://doi.org/10.1172/JCI58780.
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Research Article Oncology

Human CHCHD4 mitochondrial proteins regulate cellular oxygen consumption rate and metabolism and provide a critical role in hypoxia signaling and tumor progression

Abstract

Increased expression of the regulatory subunit of HIFs (HIF-1α or HIF-2α) is associated with metabolic adaptation, angiogenesis, and tumor progression. Understanding how HIFs are regulated is of intense interest. Intriguingly, the molecular mechanisms that link mitochondrial function with the HIF-regulated response to hypoxia remain to be unraveled. Here we describe what we believe to be novel functions of the human gene CHCHD4 in this context. We found that CHCHD4 encodes 2 alternatively spliced, differentially expressed isoforms (CHCHD4.1 and CHCHD4.2). CHCHD4.1 is identical to MIA40, the homolog of yeast Mia40, a key component of the mitochondrial disulfide relay system that regulates electron transfer to cytochrome c. Further analysis revealed that CHCHD4 proteins contain an evolutionarily conserved coiled-coil-helix-coiled-coil-helix (CHCH) domain important for mitochondrial localization. Modulation of CHCHD4 protein expression in tumor cells regulated cellular oxygen consumption rate and metabolism. Targeting CHCHD4 expression blocked HIF-1α induction and function in hypoxia and resulted in inhibition of tumor growth and angiogenesis in vivo. Overexpression of CHCHD4 proteins in tumor cells enhanced HIF-1α protein stabilization in hypoxic conditions, an effect insensitive to antioxidant treatment. In human cancers, increased CHCHD4 expression was found to correlate with the hypoxia gene expression signature, increasing tumor grade, and reduced patient survival. Thus, our study identifies a mitochondrial mechanism that is critical for regulating the hypoxic response in tumors.

Authors

Jun Yang, Oliver Staples, Luke W. Thomas, Thomas Briston, Mathew Robson, Evon Poon, Maria L. Simões, Ethaar El-Emir, Francesca M. Buffa, Afshan Ahmed, Nicholas P. Annear, Deepa Shukla, Barbara R. Pedley, Patrick H. Maxwell, Adrian L. Harris, Margaret Ashcroft

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Figure 1

CHCHD4 encodes 2 alternatively spliced and differentially expressed isoforms.

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CHCHD4 encodes 2 alternatively spliced and differentially expressed iso...
(A) Schematic representation of the CHCHD4 genomic region showing 4 exons that are subject to alternative splicing. Exons are represented by gray boxes, introns are represented by black thick lines, and patterns of alternative splicing are represented by thin lines (blue and black). Gene-specific primers (GSP) were used for PCR to examine the alternative splicing transcripts. (B) Human tissue expression analysis shows that the CHCHD4 transcripts are ubiquitously expressed. Gene-specific primers for CHCHD4.1 and CHCHD4.2 described in A were used to examine human tissue expression, as indicated by RT-PCR. GAPDH was used as a loading control. (C) The amino acid sequences encoded by CHCHD4.1 and CHCHD4.2 were aligned using the ClustalW program. The short N-terminal sequence in CHCHD4.2 is underlined. Identical (asterisk), conserved (double dot), and partially conserved (single dot) amino acid residues are indicated. (D) Western blot showing differential expression of the CHCHD4 proteins in tumor cells. HCT116, RCC4, and RCC4/VHL cells were transfected with CHCHD4 siRNA (CH) or NSC (N) siRNA. Cell lysates were analyzed by Western blot for endogenous CHCHD4 proteins (CHCHD4.1 and CHCHD4.2) as indicated (arrows).