Cells are shape shifters, rearranging themselves for diverse functions from cell division to sprouting a flagellum. But how does a cell know what shape it’s in? We’ve known that proteins can sense cellular contours on the nano scale, that is, 1 x 10-9 m, but what about the big stuff in cells on the micron scale (1 x 10-6 m) such as cytokinetic furrow which is the pinch off point between dividing mother and daughter cells? Inside a eukaryotic cell, a micron-sized structure is a major landmark.
In an ingenious use of the model lab organism, the fungus Ashbya gossypii, and precisely-sized silica beads coated with a lipid bilayer, ASCB members Andrew Bridges and Amy Gladfelter with colleagues at Dartmouth College, NH, and the Marine Biological Laboratory, MA, have shown that septins, small GTP-binding proteins, have a talent for spotting the big stuff. They report in a new JCB paper that nano-scale septins are able to distinguish micron-scale curves in the membrane-like lipid-coated beads. Indeed, septins have a clear preference for curves in the 1-3 micron range and again around .3 microns. Repeating the coated bead experiments with human septins, the Dartmouth researchers came up with similar results, suggesting that septin sensing of cell contours is an evolutionarily conserved mechanism from Ashbya to Homo.
