- EC coupling in single cardiac sarcomeres
Excitation–contraction coupling results in the shortening of many individual sarcomeres along the length of a muscle fiber. Tsukamoto and colleagues develop a technique to quantitatively analyze the dynamics of intracellular calcium transients and length changes at the single sarcomere level.
- pH-sensing sAC controls lysosome pH
Lysosomes are the main degradative compartment in cells and require an acidic luminal environment for correct function. Rahman et al. show that soluble adenylyl cyclase is required for localization of the V-ATPase proton pump to lysosomes and therefore lysosomal acidification and function.
- Secondary anionic lipid site in Kir2 channels
Phospholipids are required to bind to two distinct sites on the inward rectifier potassium channel for maximal efficacy. Lee et al. show that a membrane-associating tryptophan residue in the second site can mimic the effect of phospholipid binding and cause a conformational change to reveal the primary binding site.
- Renal Cl− channel: Regulation by voltage and pH
ClC-K2 is present on the basolateral membrane of kidney epithelial cells, but little is known about its single channel properties. Pinelli et al. record unitary ClC-K2 currents from intercalated cells of mouse connecting tubules and investigate their regulation by voltage, pH, Cl−, and Ca2+.
- Purinergic signaling in spermatogonia
Male germ cell development takes place within the testes of mammals, but little is known about its regulation. Fleck et al. record from spermatogonia and Sertoli cells, both in vitro and in situ, and find evidence for P2X4- and P2X7-mediated ATP-gated currents as well as a Ca2+-activated BK conductance.
- Molecular determinants of Si transport
For the aquaporins, selectivity to water is ensured to a large extent by an arginine filter within the pore of the channel. Carpentier et al. find that selectivity to silicon is also controlled by this filter but with the involvement of additional residues that are within or close to the pore.