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.
View: Text | PDF
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

×

Figure 5

CHCHD4 proteins regulate tumor growth and angiogenesis in vivo.

Options: View larger image (or click on image) Download as PowerPoint
CHCHD4 proteins regulate tumor growth and angiogenesis in vivo. HCT116 c...
HCT116 cells stably expressing a CHCHD4 shRNA vector or 2 independent control shRNA vectors were exposed to normoxia (N) or hypoxia (H) (1% O2) for 16 hours. Whole cell lysates were assessed (A) by Western blot analysis for HIF-1α and CHCHD4 protein or (B) by ELISA for VEGF (pg/ml) expression. *P < 0.05. (C) Graph showing cell viability (% relative to control) of HCT116 cells stably expressing 2 independent CHCHD4 shRNA vectors or 2 independent control shRNA vectors. Cell viability was measured using a MTT assay (n = 6; average ± SD). (D) HCT116 cells stably expressing 2 independent CHCHD4 shRNA or control shRNA vectors were subcutaneously injected into 8 nude mice (per group) and grown as xenografts. Graph showing tumor growth (cm3) over time in days. Data are representative of 2 independent experiments (n = 8). **P < 0.01, for CHCHD4 shRNA1 versus control1 shRNA and CHCHD4 shRNA2 versus control2 shRNA, respectively. (E) Immunohistochemical analysis of HCT116 xenograft tumor sections using either an antibody control (Ab-ctrl) or CD34 staining to identify blood vessels (as indicated with arrows). (F) Graph shows average blood vessel (CD34+) count per field of view (3 independent fields for CHCHD4 shRNA2 or control2 shRNA HCT116 xenograft tumor sections). Values are expressed as average ± SD. *P < 0.05.