Regulation of nuclear actin dynamics in development and disease

Actin has essential functions both in the cytoplasm and in the nucleus, where it has been linked to key nuclear processes, from transcription to DNA damage response. The multifunctional nature of actin suggests that the cell must contain mechanisms to accurately control the cellular actin balance. Indeed, recent results have demonstrated that nuclear actin levels fluctuate to regulate the transcriptional activity of the cell and that controlled nuclear actin polymerization is required for transcription activation, cell cycle progression, and DNA repair. Intriguingly, aberrant nuclear actin regulation has been observed, for example, in cancer, signifying the importance of this process for cellular homeostasis. This review discussed the latest research on how nuclear actin is regulated, and how this influences actin-dependent nuclear processes.Peer reviewe

Regulation of nuclear actin levels and MRTF/SRF target gene expression during PC6.3 cell differentiation

Actin has important functions in both cytoplasm and nucleus of the cell, with active nuclear transport mechanisms maintaining the cellular actin balance. Nuclear actin levels are subject to regulation during many cellular processes from cell differentiation to cancer. Here we show that nuclear actin levels increase upon dif-ferentiation of PC6.3 cells towards neuron-like cells. Photobleaching experiments demonstrate that this increase is due to decreased nuclear export of actin during cell differentiation. Increased nuclear actin levels lead to decreased nuclear localization of MRTF-A, a well-established transcription cofactor of SRF. In line with MRTF-A localization, transcriptomics analysis reveals that MRTF/SRF target gene expression is first transiently activated, but then substantially downregulated during PC6.3 cell differentiation. This study therefore describes a novel cellular context, where regulation of nuclear actin is utilized to tune MRTF/SRF target gene expression during cell differentiation.Peer reviewe

Resveratrol reduces oxidative stress and cell death and increases mitochondrial antioxidants and XIAP in PC6.3-cells.

Resveratrol, a polyphenol derived e.g. from red grapes, has been shown to mediate several positive biological actions such as protection of cells against oxidative stress. It can also influence cell signaling, but the mechanisms behind its antioxidant properties are largely unknown. Here we show that RSV reduces oxidative stress and enhances cell survival in PC6.3 cells depending on the concentration. In these cells, RSV increased the levels of antioxidants, SOD2 and TRX2, and of X chromosome-linked inhibitor of apoptosis protein. RSV also activated NFκB signaling as shown using luciferase reporter constructs. These findings show that RSV regulates oxidative stress and mitochondrial antioxidants in neuronal cells. This may contribute to cell protection in various brain disorders

Sigma-1 receptor agonist PRE084 is protective against mutant huntingtin-induced cell degeneration: involvement of calpastatin and the NF-kappa B pathway

Peer reviewe

mTOR inhibition increases cell viability via autophagy induction during endoplasmic reticulum stress - An experimental and modeling study

Unfolded or misfolded proteins in the endoplasmic reticulum (ER) trigger an adaptive ER stress response known as unfolded protein response (UPR). Depending on the severity of ER stress, either autophagy-controlled survival or apoptotic cell death can be induced. The molecular mechanisms by which UPR controls multiple fate decisions have started to emerge. One such molecular mechanism involves a master regulator of cell growth, mammalian target of rapamycin (mTOR), which paradoxically is shown to have pro-apoptotic role by mutually interacting with ER stress response. How the interconnections between UPR and mTOR influence the dynamics of autophagy and apoptosis activation is still unclear. Here we make an attempt to explore this problem by using experiments and mathematical modeling. The effect of perturbed mTOR activity in ER stressed cells was studied on autophagy and cell viability by using agents causing mTOR pathway inhibition (such as rapamycin or metyrapone). We observed that mTOR inhibition led to an increase in cell viability and was accompanied by an increase in autophagic activity. It was also shown that autophagy was activated under conditions of severe ER stress but that in the latter phase of stress it was inhibited at the time of apoptosis activation. Our mathematical model shows that both the activation threshold and temporal dynamics of autophagy and apoptosis inducers are sensitive to variation in mTOR activity. These results confirm that autophagy has cytoprotective role and is activated in mutually exclusive manner with respect to ER stress levels

Detection of Hypoxia-inducible mRNAs in the Plasma of Non- Small Cell Lung Cancer Patients

Abstract Background and aims: The aim of this study was to investigate the mRNA expression levels of hypoxia-inducible factor 1α and three hypoxia-inducible genes, CA9, CA12 and OPN, in NSCLC patients' plasma and to evaluate their potential as clinical tumor markers. Lung cancer is one of the most common malignancies in the world and the leading cause of cancer-related deaths. Plasma biomarkers have not yet been available as an effective clinical tool in screening or early diagnosis of lung cancer. The discovery of new potential tumor markers would have positive impact on the clinical outcome of lung cancer patients by helping to detect the disease in an early phase. Methods: mRNA expression of HIF-1α, OPN, CA IX and CA XII was studied by quantitative real-time polymerase chain reaction (qRT-PCR). Two house-keeping genes, B2M and UBC, were used for normalization. mRNA levels were assessed in the 95 blood plasma samples of NSCLC patients and 24 blood plasma samples of healthy volunteers. The qRT-PCR results were statistically analysed. Results: No significant CA IX and CA XII expression was found to be detectable in blood plasma samples. Reasonable signals were obtained for OPN and HIF-1α and two house-keeping genes, UBC and B2M. Elevated mRNA levels were observed in cancer patients' plasma. Statistically significant difference was found between UBC and OPN mRNA levels of healthy controls and NSCLC patients. The majority of correlations between mRNA levels and clinical parameters or blood biomarkers were not statistically significant. Neither did the survival analysis show any significant relationship between survival and mRNA levels. Conclusions: Due to low levels of circulating RNA in plasma quantitative real-time polymerase chain reaction seems to be challenging for routine diagnostics. In this study, a statistically significant difference was found in UBC and OPN mRNA levels between the healthy controls and NSCLC patients. Therefore, it is possible that the plasma RNA levels have some diagnostic value, although the test specificities and sensitivities remained quite low compared to the requirements set for routine laboratory diagnostics.