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

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.

Ubiquitin-specific protease-14 reduces cellular aggregates and protects against mutant huntingtin-induced cell degeneration: involvement of the proteasome and ER stress-activated kinase IRE1α

Huntington's disease (HD) is an autosomal inherited neurological disease caused by a CAG-repeat expansion in the first exon of huntingtin gene encoding for the huntingtin protein (Htt). In HD, there is an accumulation of intracellular aggregates of mutant Htt that negatively influence cellular functions. The aggregates contain ubiquitin, and part of the HD pathophysiology could result from an imbalance in cellular ubiquitin levels. Deubiquitinating enzymes are important for replenishing the ubiquitin pool, but less is known about their roles in brain diseases. We show here that overexpression of the ubiquitin-specific protease-14 (Usp14) reduces cellular aggregates in mutant Htt-expressing cells mainly via the ubiquitin proteasome system. We also observed that the serine-threonine kinase IRE1 involved in endoplasmic reticulum (ER) stress responses is activated in mutant Htt-expressing cells in culture as well as in the striatum of mutant Htt transgenic (BACHD) mice. Usp14 interacted with IRE1 in control cells but less in mutant Htt-expressing cells. Overexpression of Usp14 in turn was able to inhibit phosphorylation of IRE1α in mutant Htt-overexpressing cells and to protect against cell degeneration and caspase-3 activation. These results show that ER stress-mediated IRE1 activation is part of mutant Htt toxicity and that this is counteracted by Usp14 expression. Usp14 effectively reduced cellular aggregates and counteracted cell degeneration indicating an important role of this protein in mutant Htt-induced cell toxicity

Identification of an alternatively spliced isoform of carbonic anhydrase XII in diffusely infiltrating astrocytic gliomas

Carbonic anhydrase XII (CA XII) is a transmembrane enzyme that is associated with neoplastic growth. CA XII has been proposed to be involved in acidification of the extracellular milieu, creating an appropriate microenvironment for rapid tumor growth. Because RNA sequence databases have indicated that two isoforms of CA XII might exist in human tissues, and because alternatively spliced protein forms have been linked to aggressive behavior of cancer cells, we designed a study to evaluate the presence of the two forms of CA XII in diffuse astrocytomas, a tumor type known for its aggressive and often noncurable behavior. Reverse transcription PCR of tumor samples surprisingly revealed that CA XII present in diffuse astrocytomas is mainly encoded by a shorter mRNA variant. We further showed by Western blotting that anti-CA XII antibody recognized both isoforms in the glioblastoma cell lines, and we then evaluated the expression of CA XII in astrocytomas using immunohistochemistry and correlated the results with various clinicopathological and molecular factors. Of 370 diffusely infiltrating astrocytomas, 363 cases (98%) showed immunoreactions for CA XII. Importantly, CA XII expression correlated with poorer patient prognosis in univariate (p = 0.010, log-rank test) and multivariate survival analyses (p = 0.039, Cox analysis). From these results, we conclude that CA XII is commonly expressed in diffuse astrocytomas and that it might be used as a biomarker of poor prognosis. The absence of 11 amino acids in the shorter isoform, which seems to be common in astrocytomas, may affect the normal quaternary structure and biological function of CA XII