Tenacibactins K–M, cytotoxic siderophores from a coral-associated gliding bacterium of the genus Tenacibaculum

HPLC/DAD-based chemical investigation of a coral-associated gliding bacterium of the genus Tenacibaculum yielded three desferrioxamine-class siderophores, designated tenacibactins K (1), L (2), and M (3). Their chemical structures, comprising repeated cadaverine–succinic acid motifs terminated by a hydroxamic acid functionality, were elucidated by NMR and negative MS/MS experiments. Compounds 1–3 were inactive against bacteria and a yeast but displayed cytotoxicity against 3Y1 rat embryonic fibroblasts and P388 murine leukemia cells at GI50 in submicromolar to micromolar ranges. Their iron-chelating activity was comparable to deferoxamine mesylate.

THE CHARACTERISTICS OF RAT EMBRYONIC FIBROBLASTS (REFS) AND RAT BONE MARROW DERIVED MESENCHYMAL STEM CELLS (RAT-BMMSCS) FROM THE WISTAR RAT: A COMPARATIVE STUDY

Objective: Rat embryonic fibroblasts (REFs) and rat bone marrow-derived mesenchymal stem cells (rat-BMMSCs) an be used as in vitro models for a variety of studies, including for degenerative diseases such as arterial ischemia, tissue engineering and development of induced pluripotent stem cells (iPSCs). Therefore, the further developments of the use of these two cells of great importance. Methods: The experiments were performed with Wistar rat, those with 15-17 d gestation (aged 32 w) as a REFs source and those aged 12 w as a BMMSCs source. Dulbecco's modified eagle medium (DMEM) was used for both cell cultures but with different media supplements. Proliferation ability was determined for both by calculating population doubling time (PDT). Characterization was performed by differentiation testing into osteocyte, chondrocyte and adipocyte cells by staining with Alizarin Red, Alcian Blue and Oil Red O and by an investigation of specific antigen characteristics using flow cytometry with positive CD90 and CD29 and negative CD34 markers. Results: Morphologically, the REFs and rat-BMMSCs had the same fibroblasts like shape. PDT was higher for the REFs than the BMMSCs (p<0.05), and both could differentiate into osteocytes, chondrocytes and adipocyte. The characteristics of the positive markers (CD29 and CD90) were higher in rat-BMMSCs than in REFs. Conclusion: In this study demonstrated that the explant method for REFs isolation and flushing method for rat-BMMSC isolation are both effective. It also showed that rat-BMMSC grow faster than REFs, and that both cells have the same differentiation ability as rat-BMMSCs but with different specific surface antigen characteristics.

Gatekeeper transcription factors regulate switch between lineage preservation and cell plasticity

SummaryReprogramming somatic cells to pluripotency by repressing lineage-instructive transcription factors (TFs) alone has not been pursued because lineage specification is thought to be regulated by transcriptional regulatory networks (TRNs) comprising of multiple TFs rather than by single pivotal “gatekeeper” TFs. Utilizing an intra-species somatic cell hybrid model, we identified Snai2 and Prrx1 as the most critical determinants of mesenchymal commitment in rat embryonic fibroblasts (REFs) and demonstrate that siRNA-mediated knockdown of either of these master regulators is adequate to convert REFs into functional adipocytes, chondrocytes or osteocytes without requiring exogenous TFs or small molecule cocktails. Furthermore, knockdown of Snai2 alone proved sufficient to transform REFs to dedifferentiated pluripotent stem-like cells (dPSCs) that formed embryoid bodies capable of triple germ-layer differentiation. These findings suggest that inhibition of a single gatekeeper TF in a lineage committed cell is adequate for acquisition of cell plasticity and reprogramming without requiring permanent genetic modification.Graphical AbstractSchematic diagram depicting transdifferentiation of REFs into adipocytes, osteocytes, chondrocytes and dedifferentiation into MSCs on individual treatment with siSnai2 or siPrrx1. dPSCs were generated only in the siSnai2 group.

Reciprocal regulation of actomyosin organization and contractility in nonmuscle cells by tropomyosins and alpha-actinins

Contractile arrays of actin and myosin II filaments drive many essential processes in nonmuscle cells, including migration and adhesion. Sequential organization of actin and myosin along one dimension is followed by expansion into a two-dimensional network of parallel actomyosin fibers, in which myosin filaments are aligned to form stacks. The process of stack formation has been studied in detail. However, factors that oppose myosin stack formation have not yet been described. Here, we show that tropomyosins act as negative regulators of myosin stack formation. Knockdown of any or all tropomyosin isoforms in rat embryonic fibroblasts resulted in longer and more numerous myosin stacks and a highly ordered actomyosin organization. The molecular basis for this, we found, is the competition between tropomyosin and alpha-actinin for binding actin. Surprisingly, excessive order in the actomyosin network resulted in smaller focal adhesions, lower tension within the network, and smaller traction forces. Conversely, disordered actomyosin bundles induced by alpha-actinin knockdown led to higher than normal tension and traction forces. Thus, tropomyosin acts as a check on alpha-actinin to achieve intermediate levels of myosin stacks matching the force requirements of the cell.

Overexpression of MRPS18-2 in Cancer Cell Lines Results in Appearance of Multinucleated Cells

Human mitochondrial ribosomal protein MRPS18-2 (S18-2) is encoded by a cellular gene that is located on the human chromosome 6p21.3. We discovered that overexpression of the S18-2 protein led to immortalization and de-differentiation of primary rat embryonic fibroblasts. Cells showed anchorage-independent growth pattern. Moreover, pathways characteristic for rapidly proliferating cells were upregulated then. It is possible that the S18-2 overexpression induced disturbance in cell cycle regulation. We found that overexpression of S18-2 protein in human cancer cell lines led to an appearance of multinucleated cells in the selected clones.