March 2017 | Volume 149, No. 3
- Acting on an impulse (or two): Advantages of high-frequency tetanic onset in skeletal muscle
Moss et al. highlight why high-frequency bursts at the onset of tetany increase force development in fast-twitch skeletal muscle fibers.
- Doublet stimulation increases Ca2+ binding to troponin C to ensure rapid force development in skeletal muscle
High-frequency paired stimuli used to initiate a tetanus result in increased force and rate of force development in skeletal muscle. Bakker et al. investigate this mechanism and find that doublet stimulation increases the amount of Ca2+ bound to troponin C, resulting in rapid force development.
- Mechanisms creating transient and sustained photoresponses in mammalian retinal ganglion cells
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.
- Electrostatic tuning of the pre- and post-hydrolytic open states in CFTR
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.
- Deletion of cytosolic gating ring decreases gate and voltage sensor coupling in 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.
- Regulation of Na+ channel inactivation by the DIII and DIV voltage-sensing domains
Hsu et al. probe voltage-gated Na+ channels that are inactivation deficient with voltage-clamp fluorometry. They find that in the time domain of an action potential, the voltage-sensing domain (VSD) of domain IV regulates fast inactivation onset while the domain III VSD determines its recovery.