The novel heart-specific RING finger protein 207 is involved in energy metabolism in cardiomyocytes

Abstract BackgroundNon-small cell lung cancer (NSCLC) causes a great number of cancer-related mortality worldwide, but the biomarkers for prognosis of NSCLC are scarce because of their inconsistent efficiency. Proteins containing RING finger domain are the key mediator for ubiquitination, which controls cell cycle and regulates tumor progression. Ring Finger Protein 180 (RNF180) has been reported to suppress gastric cancer, whereas its function in NSCLC is still unclear. In this study, the association between RNF180 expression and NSCLC as well as the effect of RNF180 in cellular proliferation and metabolism of NSCLC were investigated. MethodsQuantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemical staining were performed to analyse RNF180 levels. Moreover, RNA interference (RNAi) and lentiviral-mediated vector transfections were performed to silence and overexpress RNF180. Further, Cell Counting Kit-8 (CCK-8) was used to assess its biological function in cell proliferation. A xenograft model was used to examine RNF180 function in vivo. ResultsWe found that the expression of RNF180 was decreased in NSCLC tissues, and its expression was positively correlated with the survival rate of NSCLC patients. Furthermore, the overexpression of RNF180 in NSCLC cells suppressed their proliferation, glycolytic activities, and mitochondrial respiration in vitro, and it restricted the tumorigenicity in mice. In addition, RNF180 knockdown promoted NSCLC cell proliferation and energy metabolism, whereas these promotive effects were counteracted by C-myc inhibitor. The underlying anti-NSCLC mechanism of RNF180 involved in the down-regulation of C-myc through ubiquitin-dependent degradation, and subsequently reduced C-myc downstream: lactate dehydrogenase-A (LDHA) and hexokinase-2 (HK2). ConclusionsThese results firstly indicated the anti-tumor properties of RNF180 and its significant correlation with NSCLC, which endorses RNF180 with the potential as efficient prognostic biomarker for tumor recurrence in NSCLC.

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Abstract 105: The Novel Heart-specific Ring-finger Protein 207 Regulates Energy Metabolism in Cardiomyocytes

Circulation Research ◽

10.1161/res.119.suppl_1.105 ◽

2016 ◽

Vol 119 (suppl_1) ◽

Author(s):

Wataru Mizushima ◽

Hidehisa Takahashi ◽

Masashi Watanabe ◽

Shintarou Kinugawa ◽

Shouji Matsushima ◽

...

Keyword(s):

Heart Failure ◽

Energy Metabolism ◽

Protein Level ◽

Ring Finger ◽

Metabolomic Analysis ◽

Ring Finger Protein ◽

Finger Protein ◽

Cardiac Energy Metabolism ◽

Cardiac Energy ◽

Ring Finger Proteins

Background: Ring-finger proteins constitute a large protein family in the human genome and play essential roles in various biological processes. However, little is known about heart-specific Ring-finger proteins and those relations with cardiac functions. We performed the comprehensive analysis of the expression profiles of various kinds of Ring-finger proteins and found that Ring-finger protein 207 (RNF207) was largely expressed in the heart. The purpose of our study was to elucidate a role of RNF207 in the heart. Methods and Results: First, we confirmed that RNF207 was predominantly expressed in the heart at the mRNA and protein level. Next, we examined whether the expression of RNF207 changed in transverse aortic constriction (TAC) model mice and coronary ischemic heart failure model mice . 4 weeks after TAC, mRNA level of RNF207 was significantly decreased to approximately 40% of that in sham mice. Moreover, we found that the protein level of RNF207 in the mice with heart failure was significantly reduced to around 70% of that in sham mice. Considering the well-known facts that the heart is a high-energy demanding organ and that the levels of ATP in cardiomyocytes are reduced in those model mice, we hypothesized that RNF207 got involved in cardiac energy metabolism. To investigate the hypothesis, we depleted RNF207 in rat neonatal cardiomyocytes (RNC) and performed metabolomic analysis. Metabolomic analysis revealed that ATP concentration and NADH/NAD + ratio were significantly lower and mitochondrial function was significantly reduced in RNF207 depleted RNC, compared to control NRC. Next, to elucidate the molecular mechanism by which RNF207 had effect on cardiac energy metabolism, we explored RNF207-associated proteins by mass spectrometric analysis. We identified voltage-dependent anion channel 1 (VDAC1) as a RNF207-associated protein. It has been shown that mitochondrial protein VDAC1 plays a crucial role in mitochondrial functions, such as energy metabolism. We confirmed that RNF207 directly interacted with VDAC1 by in vitro binding assay. Our results strongly indicate that RNF207 functions as a regulator of cardiac energy metabolism. Conclusion: RNF207 is a novel heart-specific protein and regulates energy metabolism in cardiomyocytes.

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