Yang et al. study changes in the activity of the kidney ENaC and ROMK channels in response to variations in K+ levels in the diet. Na+ channel activity and localization changed in response to varying K+ levels, suggesting adaptation in the nephron to compensate for excess or lack of K+.

Smith et al. use a novel technique for direct measurement of solute transport from cerebrospinal fluid to brain interstitial fluid. Contrary to previous suggestions, they find no evidence for a role of aquaporin-4 in this process of extracellular transport in the central nervous system.

Contractility of smooth muscle is of vital importance. Pütz et al. reveal that the actin filament–linked protein caldesmon is indispensable for abdominal wall closure, and that in smooth muscle it promotes a relaxed state and supports the integrity of the contractile apparatus.

Hariharan and Guan find that binding of either melibiose or Na+ to their transporter, MelB, may favor MelB open states, while cooperative binding may trigger dehydration and cavity closure, thus enforcing cotransport. Cooperative binding is the core mechanism for their cotransport.

Rook et al. assess how mutations in acid-sensing ion channel 1 (ASIC1) affect channel desensitization. They establish that, contrary to previous reports, a glutamine to glycine substitution does not abolish desensitization, but causes complex pH-dependent effects on channel desensitization.

Proks et al. show that the antidepressant norfluoxetine affects the behavior of TREK-2 two-pore domain K+ channels by regulating the equilibrium between their open and closed states as well as their filter gating.

Szanto et al. use heavy water and Shaker-IR K+ channel mutants to establish that structural water molecules contribute to the inactivation of the selectivity filter of the channel. Their experimental evidence supports previous predictions stemming from molecular dynamics simulations.