Coupling factor 6 as a novel vasoactive and proatherogenic peptide in vascular endothelial cells

Pathogenesis of cardiovascular diseases: effects of mitochondrial CF6 on endothelial cell function

Cardiovascular disease (CVD) stands as a predominant global cause of morbidity and mortality, necessitating effective and cost-efficient therapies for cardiovascular risk reduction. Mitochondrial coupling factor 6 (CF6), identified as a novel proatherogenic peptide, emerges as a significant risk factor in endothelial dysfunction development, correlating with CVD severity. CF6 expression can be heightened by CVD risk factors like mechanical force, hypoxia, or high glucose stimuli through the NF-κB pathway. Many studies have explored the CF6-CVD relationship, revealing elevated plasma CF6 levels in essential hypertension, atherosclerotic cardiovascular disease (ASCVD), stroke, and preeclampsia patients. CF6 acts as a vasoactive and proatherogenic peptide in CVD, inducing intracellular acidosis in vascular endothelial cells, inhibiting nitric oxide (NO) and prostacyclin generation, increasing blood pressure, and producing proatherogenic molecules, significantly contributing to CVD development. CF6 induces an imbalance in endothelium-dependent factors, including NO, prostacyclin, and asymmetric dimethylarginine (ADMA), promoting vasoconstriction, vascular remodeling, thrombosis, and insulin resistance, possibly via C-src Ca2+ and PRMT-1/DDAH-2-ADMA-NO pathways. This review offers a comprehensive exploration of CF6 in the context of CVD, providing mechanistic insights into its role in processes impacting CVD, with a focus on CF6 functions, intracellular signaling, and regulatory mechanisms in vascular endothelial cells.

Detection of mitochondrial coupling factor 6 in placental tissues from preeclamptic pregnancies and its influence on biological behavior of trophoblast cells

Increased levels of mitochondrial coupling factor 6 (CF6) are present in the peripheral blood of patients with preeclamptic pregnancies, and are particularly evident in cases of early-onset or severe preeclampsia. The present study examined the location and expression levels of CF6 in the placental tissue and its effect on the biological behavior of trophoblast cells. Placental tissue microarrays, including placental villous cytotrophoblast and extravillous cytotrophoblast microarrays, were used to detect the location and relative expression levels of CF6 in the placenta using immunohistochemistry. It was found that CF6 was expressed in both the normal and preeclamptic placenta, but its levels were higher in the preeclamptic tissues. In addition, the effects of the hypoxic environment on the biological behaviors of trophoblast cells were investigated in the JAR and JEG-3 cell lines. Following induction of hypoxia, the expression levels of CF6 were increased. Moreover, exogenous addition of human recombinant CF6 attenuated cell invasion, but exerted no effect on cell proliferation. At the molecular level, the expression levels of MMP-2 were decreased and were accompanied with a reduction in cell invasion following addition of exogenous CF6. In conclusion, the increased expression levels of CF6 and its effects in reducing the invasive abilities of trophoblast cells may be involved in the pathogenesis of severe preeclampsia.

Marine collagen peptides reduce endothelial cell injury in diabetic rats by inhibiting apoptosis and the expression of coupling factor 6 and microparticles

The present study aimed to elucidate the role of marine collagen peptides (MCPs) in protection of carotid artery vascular endothelial cells (CAVECs) in type 2 diabetes mellitus (T2DM), and the mechanism underlying this process. In an in vivo experiment, diabetic Wistar rats were divided randomly into four groups (n=10/group): Diabetes control, and three diabetes groups administered low, medium and high doses of MCPs (2.25, 4.5 and 9.0 g/kg body weight/day, respectively). Another 10 healthy rats served as the control. In an in vitro experiment, human umbilical‑vein endothelial cells (HUVECs) were incubated in normal and high concentrations of glucose with or without MCPs (3.0, 15.0 and 30.0 mg/ml, respectively) for 24, 48 or 72 h. Blood vessel/endothelial construction, inflammatory exudation and associated molecular biomarkers in CAVECs were detected and analyzed. The results of the present study demonstrated that in rats, MCP treatment for 4 weeks significantly lowered blood glucose and attenuated endothelial thinning and inflammatory exudation in carotid‑artery vascular endothelial cells. In vitro, the high‑glucose intervention significantly increased cell apoptosis in HUVECs, and medium and high doses of MCPs (4.5 and 9.0 g/kg body weight/day, respectively) partially ameliorated this high glucose‑mediated apoptosis and decreased levels of apoptosis biomarkers. In conclusion, a moderate oral MCP dose (≥4.5 g/kg body weight/day) may be a novel therapeutic tool to protect against early cardiovascular complications associated with T2DM by inhibiting apoptosis and reducing the expression of coupling factor 6 and microparticles.

Protein moonlighting: a new factor in biology and medicine

The phenomenon of protein moonlighting was discovered in the 1980s and 1990s, and the current definition of what constitutes a moonlighting protein was provided at the end of the 1990s. Since this time, several hundred moonlighting proteins have been identified in all three domains of life, and the rate of discovery is accelerating as the importance of protein moonlighting in biology and medicine becomes apparent. The recent re-evaluation of the number of protein-coding genes in the human genome (approximately 19000) is one reason for believing that protein moonlighting may be a more general phenomenon than the current number of moonlighting proteins would suggest, and preliminary studies of the proportion of proteins that moonlight would concur with this hypothesis. Protein moonlighting could be one way of explaining the seemingly small number of proteins that are encoded in the human genome. It is emerging that moonlighting proteins can exhibit novel biological functions, thus extending the range of the human functional proteome. The several hundred moonlighting proteins so far discovered play important roles in many aspects of biology. For example, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), heat-shock protein 60 (Hsp60) and tRNA synthetases play a wide range of biological roles in eukaryotic cells, and a growing number of eukaryotic moonlighting proteins are recognized to play important roles in physiological processes such as sperm capacitation, implantation, immune regulation in pregnancy, blood coagulation, vascular regeneration and control of inflammation. The dark side of protein moonlighting finds a range of moonlighting proteins playing roles in various human diseases including cancer, cardiovascular disease, HIV and cystic fibrosis. However, some moonlighting proteins are being tested for their therapeutic potential, including immunoglobulin heavy-chain-binding protein (BiP), for rheumatoid arthritis, and Hsp90 for wound healing. In addition, it has emerged over the last 20 years that a large number of bacterial moonlighting proteins play important roles in bacteria–host interactions as virulence factors and are therefore potential therapeutic targets in bacterial infections. So as we progress in the 21st Century, it is likely that moonlighting proteins will be seen to play an increasingly important role in biology and medicine. It is hoped that some of the major unanswered questions, such as the mechanism of evolution of protein moonlighting, the structural biology of moonlighting proteins and their role in the systems biology of cellular systems can be addressed during this period.

Exaggerated vasopressor response to exercise and cerebral blood flow velocity

We studied 10 young adults, normotensive at rest, comprising a control group (n = 5) with normal blood pressure responsiveness to exercise and an experimental group exhibiting greater percentage of body fat and body mass index (BMI) than the controls, with exaggerated blood pressure (vasopressor) responsiveness to exercise (EEBPR) (n = 5). Lower absolute and varying oxygen consumption/body weight normalized units of middle cerebral arterial blood flow velocity (MCAV) were found during exercise in the experimental group (P < .01). These findings support the hypothesis that the combination of EEBPR and high BMI is associated with low MCAV that may put such individuals at risk for cerebral hypoperfusion and cognitive deficits.

Coupling factor 6-induced activation of ecto-F1F(o) complex induces insulin resistance, mild glucose intolerance and elevated blood pressure in mice

AIMS/HYPOTHESIS

Despite advances in pharmacological treatments, diabetes with hypertension continues to be a major public health problem with high morbidity and mortality rates. We recently identified a circulating peptide coupling factor 6 (CF6), which binds to the plasma membrane ATP synthase (ecto-F(1)F(o) complex), resulting in intracellular acidosis. We investigated whether overexpression of CF6 contributes to diabetes and hypertension by intracellular acidosis.

METHODS

Transgenic mice overexpressing CF6 (also known as ATP5J) were generated, and physiological, biochemical and molecular biology studies were performed.

RESULTS

CF6 overexpression elicited a sustained decrease in intracellular pH in tissues (aorta, kidney, skeletal muscle and liver, with the exception of adipose tissue) that express its receptor, the β-subunit of ecto-F(1)F(o) complex. Consistent with the receptor distribution, phospho-insulin receptor β, phosphoinositide 3-kinase activity and the phospho-Akt1:total Akt1 ratio were all decreased in the skeletal muscle and the liver in transgenic compared with wild-type mice, resulting in a decrease of plasma membrane-bound GLUT4 and an increase in hepatic glucose production. Under a high-sucrose diet, transgenic mice had insulin resistance and mild glucose intolerance; under a high-salt diet, they had elevated blood pressure with increased renal RAS-related C3 botulinum substrate 1 (RAC1)-GTP, which is an activator of mineralocorticoid receptor.

CONCLUSIONS/INTERPRETATION

Through its action on the β-subunit of ecto-F(1)F(o) complex, which results in intracellular acidosis, CF6 plays a crucial role in the development of insulin resistance and hypertension. This finding might advance our understanding of the mechanisms underlying diabetes and hypertension, possibly also providing a novel therapeutic target against cardiovascular disease.

Identification and characterization of a highly thermostable bacteriophage lysozyme

Pseudomonas aeruginosa bacteriophage phiKMV is a T7-like lytic phage. Liquid chromatography-mass spectrometry of the structural proteins revealed gene product 36 (gp36) as part of the phiKMV phage particle. The presence of a lysozyme domain in the C terminal of this protein (gp36C) was verified by turbidimetric assays on chloroform-treated P. aeruginosa PAO1 and Escherichia coli WK6 cells. The molecular mass (20,884 Da) and pI (6.4) of recombinant gp36C were determined, as were the optimal enzymatic conditions (pH 6.0 in 16.7 mM phosphate buffer) and activity (4800 U/mg). Recombinant gp36C is a highly thermostable lysozyme, retaining 26% of its activity after 2 h at 100 degrees C and 21% after autoclaving. This thermostability could prove an interesting characteristic for food conservation technology.