K201 (JTV-519) alters the spatiotemporal properties of diastolic Ca2+ release and the associated diastolic contraction during β-adrenergic stimulation in rat ventricular cardiomyocytes

K201 has previously been shown to reduce diastolic contractions in vivo during β-adrenergic stimulation and elevated extracellular calcium concentration ([Ca2+]o). The present study characterised the effect of K201 on electrically stimulated and spontaneous diastolic sarcoplasmic reticulum (SR)-mediated Ca2+ release and contractile events in isolated rat cardiomyocytes during β-adrenergic stimulation and elevated [Ca2+]o. Parallel experiments using confocal microscopy examined spontaneous diastolic Ca2+ release events at an enhanced spatiotemporal resolution. 1.0 μmol/L K201 in the presence of 150 nmol/L isoproterenol (ISO) and 4.75 mmol/L [Ca2+]o significantly decreased the amplitude of diastolic contractions to ~16% of control levels. The stimulated free Ca2+ transient amplitude was significantly reduced, but stimulated cell shortening was not significantly altered. When intracellular buffering was taken into account, K201 led to an increase in action potential-induced SR Ca2+ release. Myofilament sensitivity to Ca2+ was not changed by K201. Confocal microscopy revealed diastolic events composed of multiple Ca2+ waves (2–3) originating at various points along the cardiomyocyte length during each diastolic period. 1.0 μmol/L K201 significantly reduced the (a) frequency of diastolic events and (b) initiation points/diastolic interval in the remaining diastolic events to 61% and 71% of control levels respectively. 1.0 μmol/L K201 can reduce the probability of spontaneous diastolic Ca2+ release and their associated contractions which may limit the propensity for the contractile dysfunction observed in vivo

VANG-1 and PRKL-1 Cooperate to Negatively Regulate Neurite Formation in Caenorhabditis elegans

Neuritogenesis is a critical early step in the development and maturation of neurons and neuronal circuits. While extracellular directional cues are known to specify the site and orientation of nascent neurite formation in vivo, little is known about the genetic pathways that block inappropriate neurite emergence in order to maintain proper neuronal polarity. Here we report that the Caenorhabditis elegans orthologues of Van Gogh (vang-1), Prickle (prkl-1), and Dishevelled (dsh-1), core components of planar cell polarity (PCP) signaling, are required in a subset of peripheral motor neurons to restrict neurite emergence to a specific organ axis. In loss-of-function mutants, neurons display supernumerary neurites that extend inappropriately along the orthogonal anteroposterior (A/P) body axis. We show that autonomous and non-autonomous gene activities are required early and persistently to inhibit the formation or consolidation of growth cone protrusions directed away from organ precursor cells. Furthermore, prkl-1 overexpression is sufficient to suppress neurite formation and reorient neuronal polarity in a vang-1– and dsh-1–dependent manner. Our findings suggest a novel role for a PCP–like pathway in maintaining polarized neuronal morphology by inhibiting neuronal responses to extrinsic or intrinsic cues that would otherwise promote extraneous neurite formation

A hub-and-spoke circuit drives pheromone attraction and social behaviour in C. elegans

Innate social behaviors emerge from neuronal circuits that interpret sensory information based on an individual's own genotype, sex, and experience. The regulated aggregation behavior of C. elegans, a simple animal with only 302 neurons, is an attractive system to analyze these circuits. Wild social strains of the nematode Caenorhabditis elegans aggregate in the presence of specific sensory cues, but solitary strains do not1,2,3,4. Here we identify the RMG inter/motor neuron as the hub of a regulated circuit that controls aggregation and related behaviors. RMG is the central site of action of the neuropeptide receptor gene npr-1, which distinguishes solitary strains (high npr-1 activity) from wild social strains (low npr-1 activity); high RMG activity is essential for all aspects of social behavior. Anatomical gap junctions connect RMG to multiple classes of sensory neurons known to promote aggregation, and to ASK sensory neurons, which are implicated in male attraction to hermaphrodite pheromones5. We find that ASK neurons respond directly to pheromones, and that high RMG activity enhances ASK responses in social strains, causing hermaphrodite attraction to pheromones at concentrations that repel solitary hermaphrodites. The coordination of social behaviors by RMG suggests an anatomical hub-and-spoke model fo