Single channel properties of a volume sensitive anion channel: Lessons from noise analysis

Swelling activated anion channels have recently been recognized to play an important role in not only volume regulatory electrolyte movement, but also in organic osmolyte transport. A swelling-activated, outwardly rectifying anion channel termed VSOAC (volume-sensitive organic osmolyte/anion channel) is a major pathway for swelling-induced loss of organic osmolytes and organic anions from mammalian cells. VSOAC has been described in numerous cell types. Until recently, however, the unitary conductance and gating kinetics of VSOAC were uncertain. Stationary noise analysis and single channel measurements have produced estimates for the unitary conductance of swelling-activated, outwardly rectifying anion channels that vary by > 15-fold. This review describes our current understanding of the single channel properties of VSOAC.