Optical regulation of endogenous RhoA reveals selection of cellular responses by signal amplitude.

How protein signaling networks respond to different input strengths is an important but poorly understood problem in cell biology. For example, RhoA can promote focal adhesion (FA) growth or disassembly, but how RhoA activity mediates these opposite outcomes is not clear. Here, we develop a photoswitchable RhoA guanine nucleotide exchange factor (GEF), psRhoGEF, to precisely control endogenous RhoA activity. Using this optical tool, we discover that peak FA disassembly selectively occurs upon activation of RhoA to submaximal levels. We also find that Src activation at FAs selectively occurs upon submaximal RhoA activation, identifying Src as an amplitude-dependent RhoA effector. Finally, a pharmacological Src inhibitor reverses the direction of the FA response to RhoA activation from disassembly to growth, demonstrating that Src functions to suppress FA growth upon RhoA activation. Thus, rheostatic control of RhoA activation by psRhoGEF reveals that cells can use signal amplitude to produce multiple responses to a single biochemical signal.

Lysophosphatidylcholine exerts an anti-skin photoaging effect via heat shock protein 70 induction.

OBJECTIVE: Skin-brightening agents prevent melanogenesis and reduce melanin production. However, a lower melanin content leads to weaker protection against sunlight. In this study, we evaluated the effect of lysophosphatidylcholine (LPC) and its commercial-grade product, Lysofix Dry™ (LD), on heat shock protein 70 (HSP70) expression in epidermal cells and their anti-skin photoaging effect against ultraviolet B (UVB) and blue light. METHODS: The HSP70 induction was detected using ELISA. To confirm the inhibition of melanin synthesis by LPC or LD, the melanin content assay and gene expression were analyzed. Cell viability was assessed to verify whether LPC or LD prevents photo-induced skin damage. The split-face test was performed to confirm skin-brightening effect of LD. Cream formulation with 2% of LD and placebo were used for 8 weeks, and skin brightness (L) was measured with chromameter (CR-400, Konica Minolta). RESULTS: LPC- and LD-induced HSP70 expression in epidermal cells. LPC and LD effectively suppressed melanogenesis provoked by α-MSH in B16 cells. They also inhibited the mRNA transcription of MITF and tyrosinase under blue light irradiation. LD increased the viability of B16 and HaCaT cells after UVB and blue light irradiation in vitro. The cream containing 2% LD increased ΔL by 1.7 after 8 weeks of use, whereas the placebo led to an increase of 0.7. CONCLUSION: LPC and LD were effective in suppressing melanogenesis and enhancing cell viability under UVB and blue light via HSP70 expression. Thus, they can be considered as potent skin-brightening agents with protective effects against skin photoaging.

Genetically Encoded Biosensors Based on Fluorescent Proteins.

Genetically encoded biosensors based on fluorescent proteins (FPs) allow for the real-time monitoring of molecular dynamics in space and time, which are crucial for the proper functioning and regulation of complex cellular processes. Depending on the types of molecular events to be monitored, different sensing strategies need to be applied for the best design of FP-based biosensors. Here, we review genetically encoded biosensors based on FPs with various sensing strategies, for example, translocation, fluorescence resonance energy transfer (FRET), reconstitution of split FP, pH sensitivity, maturation speed, and so on. We introduce general principles of each sensing strategy and discuss critical factors to be considered if available, then provide representative examples of these FP-based biosensors. These will help in designing the best sensing strategy for the successful development of new genetically encoded biosensors based on FPs.

Tentonin 3/TMEM150c Confers Distinct Mechanosensitive Currents in Dorsal-Root Ganglion Neurons with Proprioceptive Function.

Touch sensation or proprioception requires the transduction of mechanical stimuli into electrical signals by mechanoreceptors in the periphery. These mechanoreceptors are equipped with various transducer channels. Although Piezo1 and 2 are mechanically activated (MA) channels with rapid inactivation, MA molecules with other inactivation kinetics have not been identified. Here we report that heterologously expressed Tentonin3 (TTN3)/TMEM150C is activated by mechanical stimuli with distinctly slow inactivation kinetics. Genetic ablation of Ttn3/Tmem150c markedly reduced slowly adapting neurons in dorsal-root ganglion neurons. The MA TTN3 currents were inhibited by known blockers of mechanosensitive ion channels. Moreover, TTN3 was localized in muscle spindle afferents. Ttn3-deficient mice exhibited the loss of coordinated movements and abnormal gait. Thus, TTN3 appears to be a component of a mechanosensitive channel with a slow inactivation rate and contributes to motor coordination. Identification of this gene advances our understanding of the various types of mechanosensations, including proprioception.

Protons inhibit anoctamin 1 by competing with calcium.

Cl(-) efflux through Ca(2+)-activated Cl(-) channels (CaCCs) in secretory epithelial cells plays a key role in the regulation of fluid secretion. The fluid and electrolyte secretion is closely related to intracellular pH. CaCCs have been known to be inhibited by intracellular acid. However, the molecular mechanism for the inhibition remains unknown. Anoctamin 1 (ANO1) is a Ca(2+)-activated Cl(-) channel that mediates numerous physiological functions including fluid secretion in secretory epithelia. However, little is known about whether ANO1 can be modulated by change of intracellular pH. Here, we demonstrate that Ca(2+)-induced activation of ANO1 and its homolog ANO2 are strongly inhibited by intracellular acid. Intracellular acid caused a rightward shift of the concentration-response curve of Ca(2+) in activating ANO1 and ANO2. To identify the location of the acid-induced inhibition, mutations were made on each of all histidine residues in cytoplasmic part of ANO1. However, none of the His-mutant showed the reduction in the acid-induced inhibition. Furthermore, mutation on Glu- or Asp-residues in the multiple acidic-amino acid regions was ineffective in blocking the acid-induced inhibition. Because the Ca(2+)-binding site of a fungal anoctamin (nhTMEM16) was uncovered by crystallography, mutagenesis was performed in this region. Surprisingly, mutations at Glu, Asp or Asn residues in the hydrophobic core that are known to be essential for Ca(2+)-induced activation of ANO1 blocked the acid-induced inhibition. These results suggest that protons interfere with Ca(2+) at the Ca(2+) binding site of ANO1. These findings provide a molecular mechanism underlying the acid-induced inhibition of ANO1, which may contribute to control fluid and electrolyte secretion in the secretory epithelia.

Two helices in the third intracellular loop determine anoctamin 1 (TMEM16A) activation by calcium.

Anoctamin 1 (ANO1)/TMEM16A is a Cl(-) channel activated by intracellular Ca(2+) mediating numerous physiological functions. However, little is known of the ANO1 activation mechanism by Ca(2+). Here, we demonstrate that two helices, "reference" and "Ca(2+) sensor" helices in the third intracellular loop face each other with opposite charges. The two helices interact directly in a Ca(2+)-dependent manner. Positively and negatively charged residues in the two helices are essential for Ca(2+)-dependent activation because neutralization of these charges change the Ca(2+) sensitivity. We now predict that the Ca(2+) sensor helix attaches to the reference helix in the resting state, and as intracellular Ca(2+) rises, Ca(2+) acts on the sensor helix, which repels it from the reference helix. This Ca(2+)-dependent push-pull conformational change would be a key electromechanical movement for gating the ANO1 channel. Because chemical activation of ANO1 is viewed as an alternative means of rescuing cystic fibrosis, understanding its gating mechanism would be useful in developing novel treatments for cystic fibrosis.

Synthesis of Vanadium Oxide Supported on Reduced Graphene Oxide for De-Nox.

Graphene has many excellent properties such as wide specific surface area, outstanding electrical mobility, and high optical transmittance. Due to these advantages, which make graphene appropriate matrix supporting vanadium for the nanocomposite. Also, depending on the synthesis process, graphene can be obtainable graphene oxide (GO) and reduced graphene oxide (RGO). Moreover, RGO has been receiving increased attention due to its nature to easily reduced to graphene, referred to as RGO, which has wide application. The purpose of this study is to investigate the characteristic of V2O5 deposited on RGO. The nanocomposite of vanadium oxide (V2O5) supported on RGO was prepared by different methods of evaporation, impregnation and impregnation with dispersant. XRD, SEM, TEM, BET and TGA analyses were used to investigate their chemical stability, and amount in vanadium oxide on RGO. This synthesis of V2O5 supported RGO is expected to be used as selective catalytic reduction (SCR) catalyst for De-NOx.