Structural identification of an polysaccharide isolated from Epimedium brevicornum and its beneficial effect on promoting osteogenesis in osteoblasts induced by high glucose

AIM

Diabetes osteoporosis (DOP) is a chronic bone metabolic disease induced by diabetes, whose morbidity continues to increase. Epimedium brevicornum Maxim (EB), a popular Chinese traditional medicine, has been used to treat bone diseases in China for thousands of years. But its material basis and specific mechanism of action are not clear.

METHODS

Epimedium brevicornum crude polysaccharide (EPE) is the main component, in this research the characterized the structure of EBPC1 purified from EPE was detected and its effects on cell proliferation, differentiation, and cytoskeletal in osteoblasts induced by high glucose.

RESULTS

The molecular weight of EBPC1 was 10.5 kDa. It was mainly comprised of glucose and galactose, and the backbone of EBPC1 was→4)-α-D-Galp-(1→4)-α-D-Galp-(1→6)-β-D-Galp-(1→6)-β-D-Galp-(1→4)-α-D-Glcp-(1→4)-α-D-Glcp-(1→. The results from in vitro experiments revealed that EBPC1 significantly increased alkaline phosphatase (ALP) activity and mineralized nodule formation in primary osteoblasts, also significantly up-regulated expression of Alp mRNA and Runx2 mRNA in the presence of EBPC1 pretreatment. Moreover, EBPC1 modulated apoptosis via the regulation of Bax/Bcl2.

CONCLUSION

These results indicate that EBPC1 treatment can promote osteogenesis during DOP, which can ameliorate apoptosis by regulating Bax/Bcl2 and accelerating osteogenesis in osteoblasts.

Improving the resolution of fluorescence nanoscopy using post-expansion labeling microscopy

The visualization of the cell ultrastructure and molecular complexes has long been reserved for electron microscopy owing to its nanometric resolution. In recent years, this monopoly has been challenged by super-resolution (SR) fluorescence microscopy, which allows the visualization of cell structures with high spatial resolution, approaching virtually molecular dimensions. However, the resolution of current SR microscopy does not systematically reach the level of the ultrastructural information provided by electron microscopy. In this review, we are discussing the potential of revealing cell ultrastructure using the recent method of expansion microscopy (ExM). In particular, we are discussing the limitations that exist in SR and ExM methods that prevent the visualization of nanometric molecular assemblies and how post-labeling expansion could help alleviate them to reveal the molecular cartography of cells with unprecedented details.

Review: Structure and Activation Mechanisms of CRAC Channels

Ca²⁺ release activated Ca²⁺ (CRAC) channels represent a primary pathway for Ca²⁺ to enter non-excitable cells. The two key players in this process are the stromal interaction molecule (STIM), a Ca²⁺ sensor embedded in the membrane of the endoplasmic reticulum, and Orai, a highly Ca²⁺ selective ion channel located in the plasma membrane. Upon depletion of the internal Ca²⁺ stores, STIM is activated, oligomerizes, couples to and activates Orai. This review provides an overview of novel findings about the CRAC channel activation mechanisms, structure and gating. In addition, it highlights, among diverse STIM and Orai mutants, also the disease-related mutants and their implications.

Critical parameters maintaining authentic CRAC channel hallmarks

Ca2+ ions represent versatile second messengers that regulate a huge diversity of processes throughout the cell's life. One prominent Ca2+ entry pathway into the cell is the Ca2+ release-activated Ca2+ (CRAC) ion channel. It is fully reconstituted by the two molecular key players: the stromal interaction molecule (STIM1) and Orai. STIM1 is a Ca2+ sensor located in the membrane of the endoplasmic reticulum, and Orai, a highly Ca2+ selective ion channel embedded in the plasma membrane. Ca2+ store-depletion leads initially to the activation of STIM1 which subsequently activates Orai channels via direct binding. Authentic CRAC channel hallmarks and biophysical characteristics include high Ca2+ selectivity with a reversal potential in the range of + 50 mV, small unitary conductance, fast Ca2+-dependent inactivation and enhancements in currents upon the switch from a Na+-containing divalent-free to a Ca2+-containing solution. This review provides an overview on the critical determinants and structures within the STIM1 and Orai proteins that establish these prominent CRAC channel characteristics.