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 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 6

Increased expression of CHCHD4 enhances HIF-1α protein stability and correlates with increased severity of tumor grade and decreased patient survival.

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Increased expression of CHCHD4 enhances HIF-1α protein stability and cor...
(A and B) Control HCT116 cells or HCT116 cells stably expressing myc-tagged CHCHD4.1 were exposed to hypoxia (1% O2) for 16 hours and treated with cycloheximide (CHX; 20 μg/ml) for the times indicated. (A) Western blot analysis showing HIF-1α and myc-tagged CHCHD4 proteins. Actin was used as a loading control. (B) Graph showing HIF-1α protein levels in A represented as a percentage of each untreated condition (t0) measured by densitometric analysis. (C) Graph showing disease-specific survival over time (years) in patients with breast cancer that have associated CHCHD4 expression below or equal to/above the median. (D–G) CHCHD4 gene expression data were retrieved from the Oncomine website ( https://www.oncomine.org/resource/login.html). Each symbol represents an individual sample. (D) Graph showing normalized CHCHD4 mRNA expression in 25 normal pancreatic duct cells (NP) and 24 pancreatic ductal carcinoma samples (DPca) analyzed from gene expression profiling data described previously (35). P = 0.005. The bar represents the median value. (E) Graph showing normalized CHCHD4 mRNA expression in grade 1, 2, and 3 breast carcinoma as indicated, analyzed from gene expression profiling data described previously (36). Significance values are indicated. The bar represents the median value. (F and G) Graphs showing (F) CHCHD4 DNA copy number (log2 transformed) in grade 1, 2, and 3 glioma and (G) in glioma tumor samples from patients taken at survival intervals (yr) as indicated, analyzed from gene expression profiling data described previously (37). The bar represents the median value. Significance values are indicated.