ON THE COVER
Fluorescence Lifetime Imaging (FLIM) reveals distinct diff erences in the sodium concentration of the nucleus, perinuclear regions, and cytosol of human embryonic kidney cells (HEK293T). Th e cells were stained with the sodium-sensitive dye CoroNaGreen AM; the color-coded image indicates low sodium levels in blue, and increasing sodium levels are indicated by a shift to green-yellow-red. Image © Meyer et al., 2019. See https://doi.org/10.1085/jgp.201912404.
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JGP study reveals that low temperatures reduce force production in mammalian skeletal muscle by trapping myosin motors in a refractory state unable to bind actin.
Evidence on two- and three-state models of the calcium regulation models of muscle contractions remain in favor of three-state models.
Low temperature traps myosin motors of mammalian muscle in a refractory state that prevents activation
The active force of mammalian skeletal muscle is reduced at low temperatures. Caremani et al. reveal that this is due to the rise of a population of myosin motors captured in a refractory state insensitive to muscle activation.
This paper describes the first extensive study of voltage-clamp recordings from WT and mutant mouse cone photoreceptors made from dark-adapted retinas without fluorescent markers. Cones can continue to adapt rapidly in bright light, even without known mechanisms of transduction modulation.
Effects of FGF14 and NaVβ4 deletion on transient and resurgent Na current in cerebellar Purkinje neurons
Purkinje neurons express voltage-gated Na channels and auxiliary proteins that facilitate rapid firing. White et al. find that Na current in isolated Purkinje cells is unaffected by loss of NaVβ4 subunits, but transient current is briefer and resurgent current is reduced without the FGF14 protein.
Methods and Approaches
Meyer et al. establish the suitability of the sodium-sensitive indicator dye CoroNaGreen for fluorescence lifetime imaging inside cells. This approach represents a valuable tool for quantitative and dynamic determination of intracellular sodium concentrations independent of dye concentration.