Many animals, ranging from vinegar flies to humans, discriminate a wide range of tastants, including sugars, bitter compounds, NaCl, and sour. However, the taste of Ca is poorly understood, and it is unclear whether animals such as Drosophila melanogaster are endowed with this sense. Here, we examined Ca taste in Drosophila and showed that high levels of Ca are aversive. The repulsion was mediated by two mechanisms-activation of a specific class of gustatory receptor neurons (GRNs), which suppresses feeding and inhibition of sugar-activated GRNs, which normally stimulates feeding. The distaste for Ca, and Ca-activated action potentials required several members of the variant ionotropic receptor (IR) family (IR25a, IR62a, and IR76b). Consistent with the Ca rejection, we found that high concentrations of Ca decreased survival. We conclude that gustatory detection of Ca represents an additional sense of taste in Drosophila and is required for avoiding toxic levels of this mineral.

Controlled transport of multiple individual nanostructures is crucial for nanoassembly and nanodelivery but is challenging because of small particle size. Although atomic force microscopy and optical and magnetic tweezers can control single particles, it is extremely difficult to scale these technologies for multiple structures. Here, we demonstrate a "nano-conveyer-belt" technology that permits simultaneous transport and tracking of multiple individual nanospecies in a selected direction. The technology consists of two components: nanocontainers, which encapsulate the nanomaterials transported, and nanoconveyer arrays, which use magnetic force to manipulate individual or aggregate nanocontainers. This technology is extremely versatile. For example, nanocontainers encapsulate quantum dots or rods and superparamagnetic iron oxide nanoparticles in <100 nm nanocontainers, the smallest magnetic composites to have been simultaneously moved and optically tracked. Similarly, the nanoconveyers consist of patterned microdisks or zigzag nanowires, whose dimensions can be controlled through micropatterning. The nanoconveyer belt technology could impact multiple fields, including nanoassembly, biomechanics, nanomedicine, and nanofluidics.

Transient Receptor Potential Canonical (TRPC) proteins form nonselective cation channels commonly known to be activated downstream from receptors that signal through phospholipase C (PLC). Although TRPC3/C6/C7 can be directly activated by diacylglycerols produced by PLC breakdown of phosphatidylinositol 4,5-bisphosphate (PIP 2 ), the mechanism by which the PLC pathway activates TRPC4/C5 remains unclear. We show here that TRPC4 activation requires coincident stimulation of G i/o subgroup of G proteins and PLCδ, with a preference for PLCδ1 over PLCδ3, but not necessarily the PLCβ pathway commonly thought to be involved in receptor-operated TRPC activation. In HEK293 cells coexpressing TRPC4 and G i/o -coupled μ opioid receptor, μ agonist elicited currents biphasically, with an initial slow phase preceding a rapidly developing phase. The currents were dependent on intracellular Ca 2+ and PIP 2 . Reducing PIP 2 through phosphatases abolished the biphasic kinetics and increased the probability of channel activation by weak G i/o stimulation. In both HEK293 cells heterologously expressing TRPC4 and renal carcinoma-derived A-498 cells endogenously expressing TRPC4, channel activation was inhibited by knocking down PLCδ1 levels and almost completely eliminated by a dominant-negative PLCδ1 mutant and a constitutively active RhoA mutant. Conversely, the slow phase of G i/o -mediated TRPC4 activation was diminished by inhibiting RhoA or enhancing PLCδ function. Our data reveal an integrative mechanism of TRPC4 on detection of coincident G i/o , Ca 2+ , and PLC signaling, which is further modulated by the small GTPase RhoA. This mechanism is not shared with the closely related TRPC5, implicating unique roles of TRPC4 in signal integration in brain and other systems.Canonical TRPs (TRPC1-7) are the most homologous to the prototypical Drosophila TRP and are believed to be activated downstream of phospholipase C (PLC) (1). In both heterologous and native systems, stimulating PLCβ via the G q/11 subgroup of G proteins is commonly used to activate TRPC channels. Recent studies, however, also suggest a role for G i/o subgroup of G proteins in the activation of TRPC4/C5 (2-4).TRPC4 is implicated in the regulation of microvascular permeability (5), renal cancer proliferation (6, 7), neurotransmitter release (8), intestinal contraction and motility (9), neurite extension (10), epileptiform burst firing, and seizure-induced neurodegeneration (11). The channel mediates Na + and Ca 2+ influx, causing membrane depolarization and intracellular Ca 2+ concentration ([Ca 2+ ] i ) elevation, which in turn alter cell function (12). Although advances have been made in demonstrating TRPC4 channel activation under G i/o and/or PLC stimulation, as well as its dependence on [Ca 2+ ] i , a precise description of signaling events underlying the mechanism of TRPC4 activation remains elusive.Here, we distinguished the contributions of G q/11 and G i/o pathways to TRPC4 activation and uncovered a strict codependence on G i/o and PLC pathways. We focuse...

Highlights d Drosophila exhibit distinct attraction and repulsion to different carboxylic acids d A variant ionotropic receptor (IR7a) is narrowly tuned for rejecting acetic acid d IR7a is required in bitter gustatory receptor neurons for avoiding acetic acid d Acetic-acid-induced action potentials depend on IR7a

Highlights d Opsins are needed for bitter taste in Drosophila d Opsins are directly activated by bitter tastants d Role for opsins in taste is independent of light and retinal d Opsins sense low levels of tastants via a signaling cascade that includes TRPA1

BACKGROUND AND PURPOSETransient receptor potential canonical (TRPC) channels play important roles in a broad array of physiological functions and are involved in various diseases. However, due to a lack of potent subtype-specific inhibitors the exact roles of TRPC channels in physiological and pathophysiological conditions have not been elucidated. EXPERIMENTAL APPROACHUsing fluorescence membrane potential and Ca 2+ assays and electrophysiological recordings, we characterized new 2-aminobenzimidazole-based small molecule inhibitors of TRPC4 and TRPC5 channels identified from cell-based fluorescence high-throughput screening. KEY RESULTSThe original compound, M084, was a potent inhibitor of both TRPC4 and TRPC5, but was also a weak inhibitor of TRPC3. Structural modifications of the lead compound resulted in the identification of analogues with improved potency and selectivity for TRPC4 and TRPC5 channels. The aminobenzimidazole derivatives rapidly inhibited the TRPC4-and TRPC5-mediated currents when applied from the extracellular side and this inhibition was independent of the mode of activation of these channels. The compounds effectively blocked the plateau potential mediated by TRPC4-containing channels in mouse lateral septal neurons, but did not affect the activity of heterologously expressed TRPA1, TRPM8, TRPV1 or TRPV3 channels or that of the native voltage-gated Na + , K + and Ca 2+ channels in dissociated neurons.

In the central nervous system, canonical transient receptor potential (TRPC) channels have been implicated in mediating neuronal excitation induced by stimulating metabotropic receptors, including group 1 metabotropic glutamate receptors (mGluRs). Lateral septal (LS) neurons express high levels of TRPC4 and group I mGluRs. However, to what extent native TRPC4-containing channels (TRPC4-cc) are activated as well as the impact of different levels of TRPC4-cc activation on neuronal excitability remain elusive. Here, we report that stimulating LS neurons with group I mGluR agonist, (S)-3,5-DHPG, causes either an immediate increase in firing rate or an initial burst followed by a pause of firing, which can be correlated with below-threshold-depolarization (BTD) or above-threshold-plateau-depolarization (ATPD), respectively, in whole-cell recordings. The early phase of BTD and the entire ATPD are completely absent in neurons from TRPC4−/− mice. Moreover, in the same LS neurons, BTD can be converted to ATPD at more depolarized potentials or with a brief current injection, suggesting that BTD and ATPD may represent partial and full activations of TRPC4-cc, respectively. We show that coincident mGluR stimulation and depolarization is required to evoke strong TRPC4-cc current, and Na+ and Ca2+ influx, together with dynamic changes of intracellular Ca2+, are essential for ATPD induction. Our results suggest that TRPC4-cc integrates metabotropic receptor stimulation with intracellular Ca2+ signals to generate two interconvertible depolarization responses to affect excitability of LS neurons in distinct fashions.

Background: Genomic duplications involving the smooth muscle myosin heavy chain gene, MYH11, are associated with increased risk for acute aortic dissections. Results: MYH11 overexpression causes increased turnover of contractile proteins through increased autophagy. Conclusion: MYH11 duplications may predispose to aortic disease through increased turnover of contractile proteins and disruption of contractile signaling. Significance: Increased protein turnover may be an important mechanism by which genomic duplications cause human disease.