Biophysical analysis of the effect of chemical modification by 4-oxononenal on the structure, stability, and function of binding immunoglobulin protein (BiP)

Saikosaponin D Inducing Apoptosis and Autophagy through the Activation of Endoplasmic Reticulum Stress in Glioblastoma

Saikosaponin D (SSD), a saponin derivative, is extracted from Bupleurum falcatum. It exhibits an inhibitory effect on a number of tumor cells and is relatively safe when used at therapeutic doses. However, its effects on glioblastoma multiforme (GBM) have not been fully explored. This study is aimed at investigating the cytotoxic effects of SSD in GBM cell lines. SSD induces apoptosis and autophagy by activating endoplasmic reticulum (ER) stress in GBM cells. GBM cell proliferation activity and morphology were observed using the Cell Counting Kit-8 assay and hematoxylin and eosin staining. Hoechst 33258 fluorescence staining and flow cytometry were performed to assess apoptosis. Western blotting and immunocytochemical staining were used to detect protein expression and distribution. SSD significantly inhibited the proliferation of RG-2, U87-MG, and U251 cells in a dose-dependent manner, and the proportion of apoptotic cells increased significantly. Additionally, the expressions of ER-, apoptosis-, and autophagy-related proteins were significantly upregulated and distributed in the cytoplasm and nucleus. Therefore, SSD may be considered a novel treatment option for GBM. This study demonstrated the anti-GBM effect of SSD from the perspectives of cell apoptosis and autophagy.

Structural, thermodynamic and functional studies of human 71 kDa heat shock cognate protein (HSPA8/hHsc70)

Human 71 kDa heat shock cognate protein (HSPA8, also known as Hsc70, Hsp70-8, Hsc71, Hsp71 or Hsp73) is a constitutively expressed chaperone that is critical for cell proteostasis. In the cytosol, HSPA8 plays a pivotal role in folding and refolding, facilitates protein trafficking across membranes and targets proteins for degradation, among other functions. Here, we report an in solution study of recombinant HSPA8 (rHSPA8) using a variety of biophysical and biochemical approaches. rHSPA8 shares several structural and functional similarities with others human Hsp70s. It has two domains with different stabilities and interacts with adenosine nucleotides with dissociation constants in the low micromolar range, which were higher in the presence of Mg²⁺. rHSPA8 showed lower ATPase activity than its homolog HSPA5/hGrp78/hBiP, but it was 4-fold greater than that of recombinant HSPA1A/hHsp70-1A, with which it is 86% identical. Small angle X-ray scattering indicated that rHSPA8 behaved as an elongated monomeric protein in solution with dimensions similar to those observed for HSPA1A. In addition, rHSPA8 showed structural flexibility between its compacted and extended conformations. The data also indicated that HSPA8 has capacity in preventing the aggregation of model client proteins. The present study expands the understanding of the structure and activity of this chaperone and aligns with the idea that human homologous Hsp70s have divergent functions.

Salidroside inhibits the proliferation and migration of gastric carcinoma cells and tumor growth via the activation of ERS-dependent autophagy and apoptosis

The endoplasmic reticulum stress (ERS)-induced autophagy and apoptosis are favorable for the suppression of many cancer types. Salidroside (Salid) has been proven to be capable of inducing the apoptosis of many cancer cells. However, the underlying mechanisms and whether Salid can activate the autophagic system have still not been explained thoroughly. Herein, the inhibition effect of Salid on the growth and progress of gastric cancer and the underlying mechanisms were investigated. With the SGC-7901 cells acting as the cancer model cells, we ascertained that Salid exerted a superior antagonism effect on the growth and migration of gastric cancer cells in a dose-dependent manner. Additionally, Salid exhibited strong capacity to induce cell apoptosis by the down-regulation of proliferation-related genes (Ki67 and PCNA), increase in the pro-apoptotic protein C-caspase-3, and changing the levels of other related genes. A mechanism study revealed that the levels of the ERS-related genes, such as CHOP, C-caspase-12, GADD34, and BiP, in the SGC-7901 cells dramatically changed post-treatment by Salid, indicating the involvement of ERS in Salid-inducing cell apoptosis. In addition, the increased LC3⁺ autophagic vacuoles, enhanced conversion of LC3-I to LC3-II, and inhibition of the PI3K/Akt/mTOR pathway further confirmed the activation of autophagy induced by Salid. Importantly, the effect of Salid in regulating the levels of autophagy-related proteins or the signaling pathway could be markedly depressed by co-incubating with Wortmannin (Wort), an autophagy inhibitor. The final evaluation of the tumor therapy efficacy exhibited satisfactory cancer growth inhibition by Salid with negligible toxicity to normal tissues. In summary, the present work provides a comprehensive effective evaluation of Salid for treating gastric cancer. The detailed investigation of the underlying mechanisms may offer a rational reference for the future applications of Salid in clinic.

The endoplasmic reticulum stress (ERS)-induced autophagy and apoptosis are favorable for the suppression of many cancer types.