Transfection of Sponge Cells and Intracellular Localization of Cancer-Related MYC, RRAS2, and DRG1 Proteins.

The determination of the protein's intracellular localization is essential for understanding its biological function. Protein localization studies are mainly performed on primary and secondary vertebrate cell lines for which most protocols have been optimized. In spite of experimental difficulties, studies on invertebrate cells, including basal Metazoa, have greatly advanced. In recent years, the interest in studying human diseases from an evolutionary perspective has significantly increased. Sponges, placed at the base of the animal tree, are simple animals without true tissues and organs but with a complex genome containing many genes whose human homologs have been implicated in human diseases, including cancer. Therefore, sponges are an innovative model for elucidating the fundamental role of the proteins involved in cancer. In this study, we overexpressed human cancer-related proteins and their sponge homologs in human cancer cells, human fibroblasts, and sponge cells. We demonstrated that human and sponge MYC proteins localize in the nucleus, the RRAS2 in the plasma membrane, the membranes of the endolysosomal vesicles, and the DRG1 in the cell's cytosol. Despite the very low transfection efficiency of sponge cells, we observed an identical localization of human proteins and their sponge homologs, indicating their similar cellular functions.

In Vivo Skin Regeneration and Wound Healing Using Cell Micro-Transplantation.

Background: The accumulation of senescent cells in tissues alters tissue homeostasis and affects wound healing. It is also considered to be the main contributing factor to aging. In addition to losing their ability to divide, senescent cells exert detrimental effects on surrounding tissues through their senescence-associated secretory phenotype (SASP). They also affect stem cells and their niche, reducing their capacity to divide which increasingly reduces tissue regenerative capacity over time. The aim of our study was to restore aged skin by increasing the fraction of young cells in vivo using a young cell micro-transplantation technique on Fischer 344 rats. Employing the same technique, we also used wild-type skin fibroblasts and stem cells in order to heal Dominant Dystrophic Epidermolysis Bulosa (DDEB) wounds and skin blistering. Results: We demonstrate that implantation of young fibroblasts restores cell density, revitalizes cell proliferation in the dermis and epidermis, rejuvenates collagen I and III matrices, and boosts epidermal stem cell proliferation in rats with advancing age. We were also able to reduce blistering in DDEB rats by transplantation of skin stem cells but not skin fibroblasts. Conclusions: Our intervention proves that a local increase of young cells in the dermis changes tissue homeostasis well enough to revitalize the stem cell niche, ensuring overall skin restoration and rejuvenation as well as healing DDEB skin. Our method has great potential for clinical applications in skin aging, as well as for the treatment of various skin diseases.

NME6 is a phosphotransfer-inactive, monomeric NME/NDPK family member and functions in complexes at the interface of mitochondrial inner membrane and matrix.

BACKGROUND: NME6 is a member of the nucleoside diphosphate kinase (NDPK/NME/Nm23) family which has key roles in nucleotide homeostasis, signal transduction, membrane remodeling and metastasis suppression. The well-studied NME1-NME4 proteins are hexameric and catalyze, via a phospho-histidine intermediate, the transfer of the terminal phosphate from (d)NTPs to (d)NDPs (NDP kinase) or proteins (protein histidine kinase). For the NME6, a gene/protein that emerged early in eukaryotic evolution, only scarce and partially inconsistent data are available. Here we aim to clarify and extend our knowledge on the human NME6. RESULTS: We show that NME6 is mostly expressed as a 186 amino acid protein, but that a second albeit much less abundant isoform exists. The recombinant NME6 remains monomeric, and does not assemble into homo-oligomers or hetero-oligomers with NME1-NME4. Consequently, NME6 is unable to catalyze phosphotransfer: it does not generate the phospho-histidine intermediate, and no NDPK activity can be detected. In cells, we could resolve and extend existing contradictory reports by localizing NME6 within mitochondria, largely associated with the mitochondrial inner membrane and matrix space. Overexpressing NME6 reduces ADP-stimulated mitochondrial respiration and complex III abundance, thus linking NME6 to dysfunctional oxidative phosphorylation. However, it did not alter mitochondrial membrane potential, mass, or network characteristics. Our screen for NME6 protein partners revealed its association with NME4 and OPA1, but a direct interaction was observed only with RCC1L, a protein involved in mitochondrial ribosome assembly and mitochondrial translation, and identified as essential for oxidative phosphorylation. CONCLUSIONS: NME6, RCC1L and mitoribosomes localize together at the inner membrane/matrix space where NME6, in concert with RCC1L, may be involved in regulation of the mitochondrial translation of essential oxidative phosphorylation subunits. Our findings suggest new functions for NME6, independent of the classical phosphotransfer activity associated with NME proteins.

Mutual interactions between telomere heterogeneity and cell culture growth dynamics shape stochasticity of cell aging.

Mathematical modeling and computational simulations are often used to explain the stochastic nature of cell aging. The models published thus far are based on the molecular mechanisms of telomere biology and how they dictate the dynamics of cell culture proliferation. However, the influence of cell growth conditions on telomere dynamics has been widely overlooked. These conditions include interactions with surrounding cells through contact inhibition, gradual accumulation of non-dividing cells, culture propagation and other cell culture maintenance factors. In order to follow the intrinsic growth dynamics of normal human fibroblasts we employed the fluorescent dye DiI and FACS analysis which can distinguish cells that undergo different numbers of divisions within culture. We observed rapid generation of cell subpopulations undergoing from 0 to 9 divisions within growing cultures at each passage analyzed. These large differences in number of divisions among individual cells guarantee a strong impact on generation of telomere length heterogeneity in normal cell cultures and suggest that culture conditions should be included in future modeling of cell senescence.

Telomeres, Nutrition, and Longevity: Can We Really Navigate Our Aging?

Telomeres are dynamic chromosome-end structures that serve as guardians of genome stability. They are known to be one of the major determinants of aging and longevity in higher mammals. Studies have demonstrated a direct correlation between telomere length and life expectancy, stress, DNA damage, and onset of aging-related diseases. This review discusses the most important factors that influence our telomeres. Various genetic and environmental factors such as diet, physical activity, obesity, and stress are known to influence health and longevity as well as telomere dynamics. Individuals currently have the opportunity to modulate the dynamics of their aging and health span, monitor these processes, and even make future projections by following their telomere dynamics. As telomeres react to positive as well as negative health factors, we should be able to directly influence our telomere metabolism, slow their deterioration, and diminish our aging and perhaps extend our life and health span.

Telomere Q-PNA-FISH--reliable results from stochastic signals.

Structural and functional analysis of telomeres is very important for understanding basic biological functions such as genome stability, cell growth control, senescence and aging. Recently, serious concerns have been raised regarding the reliability of current telomere measurement methods such as Southern blot and quantitative polymerase chain reaction. Since telomere length is associated with age related pathologies, including cardiovascular disease and cancer, both at the individual and population level, accurate interpretation of measured results is a necessity. The telomere Q-PNA-FISH technique has been widely used in these studies as well as in commercial analysis for the general population. A hallmark of telomere Q-PNA-FISH is the wide variation among telomere signals which has a major impact on obtained results. In the present study we introduce a specific mathematical and statistical analysis of sister telomere signals during cell culture senescence which enabled us to identify high regularity in their variations. This phenomenon explains the reproducibility of results observed in numerous telomere studies when the Q-PNA-FISH technique is used. In addition, we discuss the molecular mechanisms which probably underlie the observed telomere behavior.

Tebrophen--an old polyphenol drug with anticancer potential.

In vitro high-throughput screening was carried out in order to detect new activities for old drugs and to select compounds for the drug development process comprising new indications. Tebrophen, a known antiviral drug, was found to inhibit activities on inflammation and cancer related targets. In primary screening this semisynthetic halogenated polyphenol was identified to inhibit the activities of kinases ZAP-70 and Lck (IC50 0.34 µM and 16 µM, respectively), as well as hydrolase DPPIV (at 80 µM 41% inhibition). Next, it showed no cytotoxic effects on standard cell lines within 24 h. However, tebrophen slowed propagation of breast cancer (MDA-MB-231), osteosarcoma (U2OS) and cervical carcinoma (HeLa), through at least 35 population doublings in a dose-dependent manner. It completely stopped the division of the prostate cancer (PC3) cell line at 50 µM concentration and the cells entered massive cell death in less than 20 days. On the other hand, tebrophen did not influence the growth of normal fibroblasts. According to the measured oxidative burst and estimated in silico parameters its direct antioxidative ability is limited. The obtained results indicate that tebrophen can be considered a promising lead molecule for generating more soluble derivatives with specific anticancer efficacy.

Abrupt telomere shortening in normal human fibroblasts.

Aging is one of the most basic properties of living organisms. Abundant evidence supports the idea that cell senescence underlies organismal aging in higher mammals. Therefore, examining the molecular mechanisms that control cell and replicative senescence is of great interest for biology and medicine. Several discoveries strongly support telomere shortening as the main molecular mechanism that limits the growth of normal cells. Although cultures gradually approach their growth limit, appearance of individual senescent cells is sudden and stochastic. A theoretical model of abrupt telomere shortening has been proposed in order to explain this phenomenon, but until now there was no reliable experimental evidence supporting this idea. Here, we have employed novel methodology to provide evidence for the generation of extrachromosomal circular telomeric DNA as a result of abrupt telomere shortening in normal human fibroblasts. This mechanism ensures heterogeneity in growth potential among individual cells, which is crucial for gradual progression of the aging process.