The mitochondrial respiratory chain is essential for oxidative phosphorylation and comprises multiple complexes, including cytochrome c oxidase, assembled in macromolecular supercomplexes. Little is known about factors that contribute to supercomplex organization. Here we identify COX7RP as a factor that promotes supercomplex assembly. Cox7rp-knockout mice exhibit decreased muscular activity and heat production failure in the cold due to reduced COX activity. In contrast, COX7RP-transgenic mice exhibit increased exercise performance with increased cytochrome c oxidase activity. Two-dimensional blue native electrophoresis reveals that COX7RP is a key molecule that promotes assembly of the III 2 /IV n supercomplex with complex I. Our study identified COX7RP as a protein that functions in I/III 2 /IV n supercomplex assembly and is required for full activity of mitochondrial respiration.

Vitamin K is a fat-soluble vitamin that is necessary for blood coagulation. In addition, it has bone-protective effects. Vitamin K functions as a cofactor of g-glutamyl carboxylase (GGCX), which activates its substrates by carboxylation. These substrates are found throughout the body and examples include hepatic blood coagulation factors. Furthermore, vitamin K functions as a ligand of the nuclear receptor known as steroid and xenobiotic receptor (SXR) and its murine ortholog, pregnane X receptor (PXR). We have previously reported on the bone-protective role of SXR/PXR signaling by demonstrating that systemic Pxr-knockout mice displayed osteopenia. Because systemic Ggcx-knockout mice die shortly after birth from severe hemorrhage, the GGCX-mediated effect of vitamin K on bone metabolism has been difficult to evaluate. In this work, we utilized Ggcx-floxed mice to generate osteoblastspecific GGCX-deficient (Ggcx Dobl/Dobl ) mice by crossing them with Col1-Cre mice. The bone mineral density (BMD) of Ggcx Dobl/Dobl mice was significantly higher than that of control Col1-Cre (Ggcx +/+ ) mice. Histomorphometrical analysis of trabecular bones in the proximal tibia showed increased osteoid volume and a higher rate of bone formation in Ggcx Dobl/Dobl mice. Histomorphometrical analysis of cortical bones revealed a thicker cortical width and a higher rate of bone formation in Ggcx Dobl/Dobl mice. Electron microscopic examination revealed disassembly of mineralized nodules and aberrant calcification of collagen fibers in Ggcx Dobl/Dobl mice. The mechanical properties of bones from Ggcx Dobl/Dobl mice tended to be stronger than those from control Ggcx +/+ mice. These results suggest that GGCX in osteoblasts functions to prevent abnormal mineralization in bone formation, although this function may not be a prerequisite for the bone-protective effect of vitamin K.

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Low-grade and early-stage endometrial cancer usually has a favorable prognosis, whereas recurrent or metastatic disease is often difficult to cure. Thus, the molecular mechanisms underlying advanced pathophysiology remain to be elucidated. From the perspective of the origin of advanced endometrial cancer, the characterization of cancer stem-like cells (CSCs) will be the first step toward the development of clinical management. We established long-term culturable patient-derived cancer cells (PDCs) from patient endometrial tumors by spheroid cell culture, which is favorable for the enrichment of CSCs. PDC-derived xenograft tumors were generated in immunodeficient NOD/Shi-scid, IL-2RγKO Jic mice. Morphologically, PDCs derived from three distinct patient samples and their xenograft tumors recapitulated the corresponding original patient tumors. Of note, CSC-related genes including ALDH1A1 were upregulated in all of these PDCs, and the therapeutic potentiality of aldehyde dehydrogenase inhibitors was demonstrated. In addition, these PDCs and their patient-derived xenograft (PDX) models exhibited distinct characteristics on the basis of their hormone responsiveness and metastatic features. Interestingly, genes associated with inflammation and tumor immunity were upregulated by 17β-estradiol in PDC lines with high estrogen receptor expression and were also overexpressed in secondary PDCs obtained from metastatic tumor models. These results suggest that PDC and PDX models from endometrial cancer specimens would be useful to elucidate CSC traits and to develop alternative diagnostic and therapeutic options for advanced disease.

Mitochondria are essential organelles to efficiently produce ATP by ATP-synthase, which uses a proton-gradient generated by respiratory chain complexes. We previously demonstrated that COX7RP/COX7A2L/SCAF1 is a key molecule that promotes respiratory supercomplex assembly and regulates energy generation. The contribution of COX7RP to metabolic homeostasis, however, remains to be clarified. In the present study, we showed a metabolic phenotype of Cox7rp knockout (Cox7rpKO) mice, which exhibit lower blood glucose levels after insulin or pyruvate injection. Notably, ATP synthesis rate was reduced in Cox7rpKO mice liver, in accordance with decreased percentages of complex III subunit RISP and complex IV subunit COX1 involved in I + III + IV supercomplex fraction. The present findings suggest that COX7RP-mediated mitochondrial respiration plays crucial roles in the regulation of glucose homeostasis and its impairment will lead to the pathophysiology of metabolic states.

BackgroundFish oil is known to improve lifestyle-related diseases. These effects occur partly via activation of PPARs by the n-3 polyunsaturated fatty acids included abundantly in fish oil. We investigated fish oil functions on glucose and lipid metabolism that are both dependent on and independent of PPARs pathway.MethodsMice were fed a diet containing 30 en% beef tallow (B diet) for twelve weeks to induce obesity. The mice were then divided into two groups which were fed either a B diet or a diet containing 30 en% fish oil (F diet). Each group was further divided into two groups which were administered PPARα and γ antagonists or vehicle once a day for three weeks.ResultsThe F diet groups showed lower triglyceride levels in plasma and liver than the B diet groups, but PPARs antagonists did not affect the triglyceride levels in either diet groups. The F diet groups also showed improvement of glucose tolerance compared with the B diet groups. However, PPARs antagonists made glucose tolerance worse in the F diet group but improved it in the B diet group. Therefore, by the administration of antagonists, glucose tolerance was inversely regulated between the B and F diets, and hypolipidemic action in the plasma and liver of the F diet group was not affected.ConclusionThese results suggest that fish oil decreases lipid levels in plasma and liver via PPARs pathway-independent mechanism, and that glucose tolerance is inversely regulated by PPARs antagonists under diets containing different oils.

Vitamin K is a fat-soluble vitamin that plays important roles in blood coagulation and bone metabolism. One of its functions is as a co-factor for γ-glutamyl carboxylase (Ggcx). Conventional knockout of Ggcx causes death shortly after birth in homozygous mice. We created Ggcx-floxed mice by inserting loxP sequences at the sites flanking exon 6 of Ggcx. By mating these mice with albumin-Cre mice, we generated Ggcx-deficient mice specifically in hepatocytes (GgcxΔliver/Δliver mice). In contrast to conventional Ggcx knockout mice, GgcxΔliver/Δliver mice had very low activity of Ggcx in the liver and survived several weeks after birth. Furthermore, compared with heterozygous mice (Ggcx+/Δliver), GgcxΔliver/Δliver mice had shorter life spans. GgcxΔliver/Δliver mice displayed bleeding diathesis, which was accompanied by decreased activity of coagulation factors II and IX. Ggcx-floxed mice can prove useful in examining Ggcx functions in vivo.