Science 345, 693–697 (2014)

Credit: SCIENCE

Phospholipids (PLs) containing polyunsaturated acyl chains have functional effects on specialized membranes such as synaptic vesicles due to their ability to make membranes more malleable. To gain new insights into the functions of polyunsaturated PLs in membrane fission, Pinot et al. examined the effect of varying the ratio between mono- and polyunsaturated PLs on the function of the fission machinery—consisting of endophilin and the GTPase dynamin—on model membranes. Polyunsaturated PLs induced faster hydrolysis of GTP by dynamin and eliminated dynamin's sharp response to membrane curvature. Electron and light microscopy showed that polyunsaturated PLs sensitize membranes to the mechanical activities of the fission machinery. Using membrane deformation agents and a specific dynamin inhibitor, the authors found further evidence that polyunsaturated PLs facilitate endocytic events under the control of the fission machinery. They also found that polyunsaturated PLs more effectively decreased the bending rigidity of the plasma membrane of cultured cells with defined fatty acids in experiments using optical tweezers. Molecular dynamics simulations and experiments using lipid packing sensors suggested a mechanism by which polyunsaturated PLs decrease the bending rigidity and lower the force threshold for generation of fission tubules—by using their flexible chain to adapt their conformation on the basis of the curvature of the membrane.