The Voltage-Gated Proton Channel Hv1 Has Two Pores, Each Controlled by One Voltage Sensor

SummaryIn voltage-gated channels, ions flow through a single pore located at the interface between membrane-spanning pore domains from each of four subunits, and the gates of the pore are controlled by four peripheral voltage-sensing domains. In a striking exception, the newly discovered voltage-gated Hv1 proton channels lack a homologous pore domain, leaving the location of the pore unknown. Also unknown are the number of subunits and the mechanism of gating. We find that Hv1 is a dimer and that each subunit contains its own pore and gate, which is controlled by its own voltage sensor. Our experiments show that the cytosolic domain of the channel is necessary and sufficient for dimerization and that the transmembrane part of the channel is functional also when monomerized. The results suggest a mechanism of gating whereby the voltage sensor and gate are one and the same

A Spinal Opsin Controls Early Neural Activity and Drives a Behavioral Light Response

SummaryNonvisual detection of light by the vertebrate hypothalamus, pineal, and retina is known to govern seasonal and circadian behaviors [1]. However, the expression of opsins in multiple other brain structures [2–4] suggests a more expansive repertoire for light regulation of physiology, behavior, and development. Translucent zebrafish embryos express extraretinal opsins early on [5, 6], at a time when spontaneous activity in the developing CNS plays a role in neuronal maturation and circuit formation [7]. Though the presence of extraretinal opsins is well documented, the function of direct photoreception by the CNS remains largely unknown. Here, we show that early activity in the zebrafish spinal central pattern generator (CPG) and the earliest locomotory behavior are dramatically inhibited by physiological levels of environmental light. We find that the photosensitivity of this circuit is conferred by vertebrate ancient long opsin A (VALopA), which we show to be a Gαi-coupled receptor that is expressed in the neurons of the spinal network. Sustained photoactivation of VALopA not only suppresses spontaneous activity but also alters the maturation of time-locked correlated network patterns. These results uncover a novel role for nonvisual opsins and a mechanism for environmental regulation of spontaneous motor behavior and neural activity in a circuit previously thought to be governed only by intrinsic developmental programs

Synaptic Clustering of Fasciclin II and Shaker: Essential Targeting Sequences and Role of Dlg

AbstractPrevious studies have shown that both the Fasciclin II (Fas II) cell adhesion molecule and the Shaker potassium channel are localized at the Drosophila neuromuscular junction, where they function in the growth and plasticity of the synapse. Here, we use the GAL4-UAS system to drive expression of the chimeric proteins CD8–Fas II and CD8–Shaker and show that the C-terminal sequences of both Fas II and Shaker are necessary and sufficient to drive the synaptic localization of a heterologous protein. Moreover, we show that the PDZ-containing protein Discs-Large (Dlg) controls the localization of these proteins, most likely through a direct interaction with their C-terminal amino acids. Finally, transient expression studies show that the pathway these proteins take to the synapse involves either an active clustering or a selective stabilization in the synaptic membrane