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ON THE COVER
Voltage-dependent activation of spHCN channels is tracked in real time using fluorophores covalently linked to a Cys in the S4 helix to reveal different components of S4 movement. Structural modeling suggests that the distinct fluorescence responses result from different constraints on the fluorophore orientation in the resting and activated states. Image © Wojciechowski et al., 2024. See https://doi.org/10.1085/jgp.202413559. - PDF Icon PDF LinkTable of Contents
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Articles
Fusion pore flux controls the rise-times of quantal synaptic responses
The impact of fusion pores on synaptic release is difficult to discern. Through analysis of miniature excitatory synaptic currents, Jackson et al. revealed a correlation between amplitude and rise-time. Modeling indicated this correlation results from the interplay between vesicle size and fusion pore flux.
ON and OFF starburst amacrine cells are controlled by distinct cholinergic pathways
ON and OFF signals in the retina are processed via parallel pathways. Gangi et al. reveal that regulation of starburst amacrine cells, which are crucial for motion detection, is different between the ON and OFF pathways, despite their morphological mirror symmetry.
Different fluorescent labels report distinct components of spHCN channel voltage sensor movement
Wojciechowlski et al. used voltage clamp fluorometry to probe the S4 helix movement in the voltage-sensing domain of the sea urchin HCN channel expressed in Xenopus oocytes. They found that when labeled with either ALEXA-488 or MTS-TAMRA, each fluorophore reported different components of S4 movement.
Mathematical modeling of intracellular osmolarity and cell volume stabilization: The Donnan effect and ion transport
Animal cells regulate their volume by actively pumping sodium and potassium ions, preventing the osmotic influx of water from bursting the cell. We have extended the pump-leak equations that are used to characterize such systems to include impermeant extracellular molecules, cation–chloride co-transporters, and the energetics of ion transport.
