MiR 206 inhibits reorganization of the cytoskeleton in melanoma cells by targeting DDX5

Purpose: To investigate the role and mechanism of microRNA-206 (miR-206) in cytoskeleton reorganization in melanoma cells. Methods: MiR-206 and RNA helicase p68 (DDX5) expression levels were measured in A375, A875, and HEM-M cells by quantitative real time polymerase chain reaction (qRT-PCR). A DDX5 overexpression cell line was constructed, and DDX5 overexpression, A375, and A875 cells were transfected with miR-206 mimic or DDX5 small interfering RNA (siRNA). Transwell assay was used to assess cell migration and invasion of A375 and A875 cells, while Luciferase reporter assay was used to determine the putative target of miR-206. DDX5, miR-206, vinculin, coronin3, and ezrin expression levels were evaluated by qRT-PCR. Protein expressions of DDX5, vinculin, coronin3, and ezrin were evaluated by western blot analysis. Results: DDX5 expression was higher and miR-206 expression lower in A375 and A875 cells when compared to HEM-M cells (p < 0.05). Knockdown of DDX5 and overexpression of miR-206 repressed invasion and migration, and inhibited expression of vinculin, coronin3, and ezrin in A375 and A875 cells (p < 0.05). However, overexpression of DDX5 reversed the effect of miR-206 on cytoskeletal protein expression. Luciferase reporter assay data confirmed that DDX5 is a direct target of miR-206 (p < 0.05). Conclusion: MiR-206 suppresses reorganization of the cytoskeleton in melanoma cells by targeting DDX5, and is thus, a promising target for the treatment of melanoma

Noise filtering tradeoffs in spatial gradient sensing and cell polarization response

<p>Abstract</p> <p>Background</p> <p>Cells sense chemical spatial gradients and respond by polarizing internal components. This process can be disrupted by gradient noise caused by fluctuations in chemical concentration.</p> <p>Results</p> <p>We investigated how external gradient noise affects spatial sensing and response focusing on noise-filtering and the resultant tradeoffs. First, using a coarse-grained mathematical model of gradient-sensing and cell polarity, we characterized three negative consequences of noise: Inhibition of the extent of polarization, degradation of directional accuracy, and production of a noisy output polarization. Next, we explored filtering strategies and discovered that a combination of positive feedback, multiple signaling stages, and time-averaging produced good results. There was an important tradeoff, however, because filtering resulted in slower polarization. Simulations demonstrated that a two-stage filter-amplifier resulted in a balanced outcome. Then, we analyzed the effect of noise on a mechanistic model of yeast cell polarization in response to gradients of mating pheromone. This analysis showed that yeast cells likely also combine the above three filtering mechanisms into a filter-amplifier structure to achieve impressive spatial-noise tolerance, but with the consequence of a slow response time. Further investigation of the amplifier architecture revealed two positive feedback loops, a fast inner and a slow outer, both of which contributed to noise-tolerant polarization. This model also made specific predictions about how orientation performance depended upon the ratio between the gradient slope (signal) and the noise variance. To test these predictions, we performed microfluidics experiments measuring the ability of yeast cells to orient to shallow gradients of mating pheromone. The results of these experiments agreed well with the modeling predictions, demonstrating that yeast cells can sense gradients shallower than 0.1% μm^-1, approximately a single receptor-ligand molecule difference between front and back, on par with motile eukaryotic cells.</p> <p>Conclusions</p> <p>Spatial noise impedes the extent, accuracy, and smoothness of cell polarization. A combined filtering strategy implemented by a filter-amplifier architecture with slow dynamics was effective. Modeling and experimental data suggest that yeast cells employ these elaborate mechanisms to filter gradient noise resulting in a slow but relatively accurate polarization response.</p

N′-(2-Hydroxy­benzyl­idene)-2-methoxy­benzohydrazide monohydrate

In the title compound, C15H14N2O3·H2O, the Schiff base mol­ecule is approximately planar, with a dihedral angle between the two aromatic rings of 10.2 (3)°. The mol­ecular structure is stabilized by O—H⋯N and N—H⋯O hydrogen bonds. In the crystal structure, the Schiff base and water mol­ecules are linked together by inter­molecular O—H⋯O hydrogen bonds, forming chains parallel to the a axis

4-Chloro-N′-(2-hydroxy­benzyl­idene)benzohydrazide monohydrate

The asymmetric unit of the title compound, C14H11ClN2O2·H2O, contains a Schiff base mol­ecule and a water mol­ecule of crystallization. The dihedral angle between the two aromatic rings is 27.3 (4)°. In the crystal structure, mol­ecules are linked into a two-dimensional network parallel to the bc plane by inter­molecular O—H⋯O and N—H⋯O hydrogen bonds involving the water mol­ecules

Galilean invariance of lattice Boltzmann models

It is well-known that the original lattice Boltzmann (LB) equation deviates from the Navier-Stokes equations due to an unphysical velocity dependent viscosity. This unphysical dependency violates the Galilean invariance and limits the validation domain of the LB method to near incompressible flows. As previously shown, recovery of correct transport phenomena in kinetic equations depends on the higher hydrodynamic moments. In this Letter, we give specific criteria for recovery of various transport coefficients. The Galilean invariance of a general class of LB models is demonstrated via numerical experiments

Cpt-Cgmp Is A New Ligand Of Epithelial Sodium Channels

Epithelial sodium channels (ENaC) are localized at the apical membrane of the epithelium, and are responsible for salt and fluid reabsorption. Renal ENaC takes up salt, thereby controlling salt content in serum. Loss-of-function ENaC mutations lead to low blood pressure due to salt-wasting, while gain-of-function mutations cause impaired sodium excretion and subsequent hypertension as well as hypokalemia. ENaC activity is regulated by intracellular and extracellular signals, including hormones, neurotransmitters, protein kinases, and small compounds. Cyclic nucleotides are broadly involved in stimulating protein kinase A and protein kinase G signaling pathways, and, surprisingly, also appear to have a role in regulating ENaC. Increasing evidence suggests that the cGMP analog, CPT-cGMP, activates αβγ-ENaC activity reversibly through an extracellular pathway in a dose-dependent manner. Furthermore, the parachlorophenylthio moiety and ribose 2’-hydroxy group of CPT-cGMP are essential for facilitating the opening of ENaC channels by this compound. Serving as an extracellular ligand, CPT-cGMP eliminates sodium self-inhibition, which is a novel mechanism for stimulating salt reabsorption in parallel to the traditional NO/cGMP/PKG signal pathway. In conclusion, ENaC may be a druggable target for CPT-cGMP, leading to treatments for kidney malfunctions in salt reabsorption

Robust Spatial Sensing of Mating Pheromone Gradients by Yeast Cells

Projecting or moving up a chemical gradient is a universal behavior of living organisms. We tested the ability of S. cerevisiae a-cells to sense and respond to spatial gradients of the mating pheromone α-factor produced in a microfluidics chamber; the focus was on bar1Δ strains, which do not degrade the pheromone input. The yeast cells exhibited good accuracy with the mating projection typically pointing in the correct direction up the gradient (∼80% under certain conditions), excellent sensitivity to shallow gradients, and broad dynamic range so that gradient-sensing was relatively robust over a 1000-fold range of average α-factor concentrations. Optimal directional sensing occurred at lower concentrations (5 nM) close to the Kd of the receptor and with steeper gradient slopes. Pheromone supersensitive mutations (sst2Δ and ste2300Δ) that disrupt the down-regulation of heterotrimeric G-protein signaling caused defects in both sensing and response. Interestingly, yeast cells employed adaptive mechanisms to increase the robustness of the process including filamentous growth (i.e. directional distal budding) up the gradient at low pheromone concentrations, bending of the projection to be more aligned with the gradient, and forming a more accurate second projection when the first projection was in the wrong direction. Finally, the cells were able to amplify a shallow external gradient signal of α-factor to produce a dramatic polarization of signaling proteins at the front of the cell. Mathematical modeling revealed insights into the mechanism of this amplification and how the supersensitive mutants can disrupt accurate polarization. Together, these data help to specify and elucidate the abilities of yeast cells to sense and respond to spatial gradients of pheromone