Potential effects of mung bean protein and a mung bean protein-polyphenol complex on oxidative stress levels and intestinal microflora in aging mice.

This study investigated the effects of mung bean protein (MPI) and a MPI-polyphenol complex on oxidative stress levels and intestinal microflora in a D-galactose-induced aging mouse model. MPI and MPI-polyphenol complex intervention significantly increased activity of superoxide dismutase (SOD) and catalase and other antioxidant enzymes, improved the abundance and diversity of intestinal flora, and decreased the Firmicutes to Bacteroidetes ratio. Among them, the complex was more conducive to the improvement of the activity of antioxidant enzymes. The addition of MPI and the MPI-polyphenol complex can help the proliferation of Bacteroidetes, Bifidobacterium and Roseburia in the intestinal tract of aging mice, and inhibit the growth of Firmicutes and Ruminococcus, and the proliferation effect of the complex on Bifidobacterium was better than that of MPI. MPI significantly upregulated five pathways related to lipid and energy metabolism. Roseburia and Muribaculaceae were negatively correlated with malondialdehyde levels and positively correlated with SOD and other antioxidant enzyme indices. Our findings showed that MPI and MPI-polyphenol complexes can delay aging in mice by reducing oxidative damage and regulating intestinal flora. We also found a strong relationship between the abundance of intestinal flora and the levels of oxidative stress-related enzymes. This study provides theoretical support for the health and anti-aging benefits of mung bean food products.

Functional rescue of Kallmann syndrome-associated prokineticin receptor 2 (PKR2) mutants deficient in trafficking.

Mutations in the G protein-coupled prokineticin receptor 2 (PKR2) are known to cause Kallmann syndrome and idiopathic hypogonadotropic hypogonadism manifesting with delayed puberty and infertility. Some of the mutant receptors are not routed to the cell surface; instead, they are trapped in the cellular secretory pathway. The cell-permeant agonists/antagonists have been used to rescue some membrane receptors that are not targeted onto the cell membrane. Here, we chose three disease-associated mutations (W178S, G234D, and P290S), which all resulted in retention of PKR2 intracellularly. We show that a small molecule PKR2 antagonist (A457) dramatically increased cell surface expression and rescued the function of P290S PKR2, but had no effect on W178S and G234D PKR2. Furthermore, we also tested chemical chaperone glycerol on the cell surface expression and function of PKR2 mutants. Treatment with 10% glycerol significantly increased the cell surface expression and signaling of P290S and W178S PKR2. These data demonstrate that some Kallmann syndrome-associated, intracellularly retained mutant PKR2 receptors can be functionally rescued, suggesting a potential treatment strategy for patients bearing such mutations.

Transglutaminase 6 interacts with polyQ proteins and promotes the formation of polyQ aggregates.

A common feature of polyglutamine (polyQ) diseases is the presence of aggregates in neuronal cells caused by expanded polyglutamine tracts. PolyQ proteins are the substrates of transglutaminase 2, and the increased activity of transglutaminase in polyQ diseases suggests that transglutaminase may be directly involved in the formation of the aggregates. We previously identified the transglutaminase 6 gene to be causative of spinocerebellar ataxia type 35 (SCA35), and we found that SCA35-associated mutants exhibited reduced transglutaminase activity. Here we report that transglutaminase 6 interacts and co-localizes with both normal and expanded polyQ proteins in HEK293 cells. Moreover, the overexpression of transglutaminase 6 promotes the formation of polyQ aggregates and the conversion of soluble polyQ into insoluble polyQ aggregates. However, SCA35-associated mutants do not affect their interactions with polyQ proteins. These data suggest that transglutaminase 6 could be involved in polyQ diseases and there may exist a common pathological link between polyQ associated SCA and SCA35.

Spinocerebellar ataxia type 35 (SCA35)-associated transglutaminase 6 mutants sensitize cells to apoptosis.

Spinocerebellar ataxia type 35 (SCA35) is an autosomal dominant neurodegenerative disorder. In our previous study, using exome sequencing and linkage analysis, two missense mutations of the transglutaminase 6 (TGM6) gene were identified as causative for SCA35. TGM6 encodes transglutaminase 6 (TG6), a member of the transglutaminase family of enzymes that catalyze the formation of a covalent bond between a free amine group and the γ-carboxamide group of protein- or peptide-bound glutamine. However, the precise role of TG6 in contributing to SCA35 remains unclear. In this study, we analyzed the subcellular distribution, expression and in vitro activity of two missense mutations of TG6 (D327G, L517W) and found that both mutants exhibited decreased transglutaminase activity and stability. Furthermore, overexpressing the TG6 mutants sensitized cells to staurosporine-induced apoptosis by increasing the activity of caspases. We propose that the pro-apoptotic role of these mutants might underlie the pathogenesis of SCA35.