Ion fluxes resolve organellar volume

Abstract

Cell Biology Animal cells continuously sample the surrounding medium, a feature accentuated in immune cells. Sampling is accomplished by trapping external medium into membrane-bound vesicles or vacuoles. These structures are promptly resolved, thus avoiding accumulation of endomembranes and volume expansion. In a variety of cultured cells, Freeman et al. found that this resolution entails conversion of spherical vacuoles into thin tubules, a process that involves marked changes in surface-to-volume ratio (see the Perspective by King and Smythe). Shrinkage of membrane-bound structures is driven by ion fluxes and subsequent osmotic transfer of water. Shriveled vacuoles attract curvature-sensing proteins that promote the extension of fine tubules. Ion channels thereby control membrane remodeling, enabling receptor recycling and proper routing of cellular cargo. Science , this issue p. [301][1]; see also p. [246][2] [1]: /lookup/doi/10.1126/science.aaw9544 [2]: /lookup/doi/10.1126/science.aba3623