- The Trichoplax adhaerens T-type calcium channel
The role of T-type calcium channels in animals without nervous systems is unknown. Smith et al. characterize TCav3 from Trichoplax adhaerens, finding expression in neurosecretory-like cells and preference for Ca2+ over Na+ via strong extracellular Ca2+ block, despite low selectivity for Ca2+ in the pore.
- Rapid rod responses in vivo
Peinado Allina et al. measure rod responses in living mice across a wide range of flash strengths and find that responses are much faster in vivo than ex vivo, though the biochemical mechanisms underlying the kinetics appear to be the same in both cases. Although RGS9 overexpression sped recovery from bright flashes, faster rod recovery did not improve the temporal resolution of scotopic vision.
- Monobody block of dual topology fluoride channels
Fibronectin domain monobodies bind to both sides of Fluc Fl− channels in a negatively cooperative way, but crystal structures show two monobodies binding simultaneously. Turman and Stockbridge resolve this contradiction by showing that monobodies block channel pores by means of a negatively charged loop.
- TRP and TRPL in photoreceptors of P. americana
Insect photoreceptors utilize two light-activated channels, TRP and TRPL, in their phototransduction cascades, but the American cockroach Periplaneta americana depends strongly on TRPL. Saari et al. show that TRPL generates high-gain and high-noise phototransduction suitable for dim light vision.
- Protein ligands for studying ion channel proteins
Chavan et al. highlight work showing that a monobody can inhibit a fluoride channel using a mechanism similar to that of a scorpion toxin blocker of potassium channels.
- Electrostatic tuning of CFTR’s open states
Gating of the CFTR channel is coupled to ATP hydrolysis such that two open states can be identified under certain conditions. Zhang and Hwang find that pore-lining mutations differentially affect the permeation properties of these open states and suggest that the internal vestibule expands upon ATP hydrolysis.
- Phasic and tonic response mechanisms in RGCs
Visual stimuli of different frequencies are encoded in the retina using transient and sustained responses. Zhao et al. describe the different strategies that are used by four types of retinal ganglion cells to shape photoresponse kinetics.
- Voltage-gate coupling in truncated BK channels
Both cellular depolarization and intracellular Ca2+ can gate open large conductance Ca2+-activated K+ channels. Zhang et al. show that the intracellular gating ring, which forms the Ca2+-sensing machinery of the channel, is also required for activated voltage sensors to effectively gate open the pore.