Interplay Between Intracellular Transport Dynamics and Liquid‒Liquid Phase Separation.

Liquid‒liquid phase separation (LLPS) is a ubiquitous process in which proteins, RNA, and biomolecules assemble into membrane-less compartments, playing important roles in many biological functions and diseases. The current knowledge on the biophysical and biochemical principles of LLPS is largely from in vitro studies; however, the physiological environment in living cells is complex and not at equilibrium. The characteristics of intracellular dynamics and their roles in physiological LLPS remain to be resolved. Here, by using single-particle tracking of quantum dots and dynamic monitoring of the formation of stress granules (SGs) in single cells, the spatiotemporal dynamics of intracellular transport in cells undergoing LLPS are quantified. It is shown that intracellular diffusion and active transport are both reduced. Furthermore, the formation of SG droplets contributes to increased spatial heterogeneity within the cell. More importantly, the study demonstrated that the LLPS of SGs can be regulated by intracellular dynamics in two stages: the reduced intracellular diffusion promotes SG assembly and the microtubule-associated transport facilitates SG coalescences. The work on intracellular dynamics not only improves the understanding of the mechanism of physiology phase separations occurring in nonequilibrium environments but also reveals an interplay between intracellular dynamics and LLPS.

Polyisocyanide hydrogels with tunable nonlinear elasticity mediate liver carcinoma cell functional response.

Hepatocellular carcinoma development is closely related to the changes in tissue mechanics induced by excess collagen deposition and crosslinking, which leads to liver fibrosis and malignant progression. The role of matrix stiffness has been widely assessed using various linearly elastic materials. However, the liver, like many soft tissues, also exhibits nonlinear elasticity by strain-stiffening, allowing cells to mechanically interact with their micromilieus which has attracted much attention in cellular processes recently. Here, we use a biomimetic hydrogel grafting of GRGDS peptide with tunable nonlinear mechanical properties, polyisocyanides (PIC), to investigate the influence of strain-stiffening on HepG2 liver cancer cell behavior by tuning PIC polymer length. Compared to short PIC polymer with lower critical stress, PIC hydrogels composed of long polymer with higher critical stress promote the motility and invasiveness of HepG2 cells, and induce more actin stress fibers and higher expression level of mechanotransducer YAP and its nuclear translocation. Strikingly, the expression of calcium-activated potassium channel KCa3.1, an important biomarker in hepatocellular carcinoma, is also affected by the mechanical property of PIC hydrogels. It was also shown that downregulating the KCa3.1 channel can be achieved by inhibiting the formation of actin fibers. Our findings imply that the strain-stiffening property of PIC hydrogels affects the expression of KCa3.1 potassium channel via mediating cytoskeletal stress fiber formation, and ultimately influences the liver carcinoma cell functional response. STATEMENT OF SIGNIFICANCE: The effect of nonlinear elasticity by strain-stiffening, is assessed in HepG2 liver cancer cell behavior by using a biomimetic hydrogel with tunable mechanical properties, polyisocyanides (PIC). PIC gels with higher critical stress promote the motility and invasiveness of HepG2 cells and induce upregulated expression levels of KCa3.1 potassium channel and YAP, but which can be suppressed by inhibiting the formation of actin fibers. Our findings imply that the strain-stiffening property of PIC gels influences the expression of KCa3.1 potassium channel via mediating cytoskeletal stress fiber formation and, ultimately affects the liver carcinoma cell functional response.

Research progress of STC2 in breast cancer.

Breast cancer ranks second in the list of most common cancers among women and brings the double burden of economy and health to women. Therefore, it is an urgent and necessary task to study the pathogenic mechanism and the treatment of breast cancer. Glycoprotein hormone is a kind of hormones to promote the growth and the development of cell and stanniocalcin 2 (STC2) is one of them. Research has shown us a various expression of SCT2 in organs and tissues and it can regulate many different pathological and physiological processes. In addition, there are a lot of previous studies that indicated a close correlation between STC2 and the development and metastasis of many cancers, which infers STC2 can serve as biomarker of certain cancers. Until now, the effects of STC2 on breast cancer have been studied widely, but research findings demonstrated two different views, one view is that STC2 plays an oncogenic role and the other is the opposite. In this paper, it will summarize and evaluate the research data and results about mammalian STC2 on breast cancer.

TGF-ß1 resulting in differential microRNA expression in bovine granulosa cells.

To explore the expression profile of the cellular miRNAs in bovine ovarian granulosa cells responding to transforming growth factor-ß1 (TGF-ß1), the effect of TGF-ß1 on cell proliferation was firstly investigated by CCK-8 method and the results showed that there was a significant inhibitory effect on bovine granulosa cell proliferation treated with 5/10 ng/mL human recombinant TGF-ß1 for 24 h compared to the control (P < 0.05). Then, we performed high-throughput sequencing of two small RNA libraries prepared from cultured bovine granulosa cells stimulated with or without 10 ng/mL human recombinant TGF-ß1. A total of 13,257,248 and 138,726,391 clean reads per library were obtained from TGF-ß1 and control groups, respectively. There were 498 and 499 bovine-specific exist miRNAs (exist miRNAs), 627 and 570 conserved known miRNAs (known miRNAs), and 593 and 585 predicted novel miRNAs in TGF-ß1 and control groups, respectively. A total of 78 miRNAs with significant differential expression, including 39 up-regulated miRNAs and 39 down-regulated miRNAs were identified in the TGF-ß1 group compared with the control. Real-time quantitative PCR analyses of bta-miR-106a and bta-miR-1434-5p showed that their up-expressions were interrupted by SB431542, an inhibitor that blocks TGFß1/Smad signaling, which supported the sequencing data. GO analysis showed involvement of the predicted genes of the differentially expressed miRNAs in a broad spectrum of cell biological processes, cell components, and molecular functions. KEGG pathway analysis of the predicted miRNA targets further indicated that these differentially expressed miRNAs are involved in various signaling pathways, such as Wnt, MAPK, and TGF-ß signaling, which might be involved in follicular development. These results provide valuable information on the composition, expression, and function of miRNAs in bovine granulosa cells responding to TGF-ß1, and will aid in understanding the molecular mechanisms of TGF-ß1 in granulosa cells.