Two-Dimensional Solvent-Mediated Phase Transformation in Lipid Membranes Induced by Sphingomyelinase

The spatial pattern changes in model raft membranes during sphingomyelinase (SMase)-induced solvent-mediated phase transformation are characterized in terms of a model that combines three major kinetic processes suggested by experimental observations: the release of sphingomyelin (SM) by the dissolution of SM-enriched domains within the raft membrane, the diffusion of SM from the dissolution sites to the reaction site in a solvent-like fluid lipid phase, and the consumption of SM by the enzymatic reaction at this reaction site, termed an SMase feature. Such processes may be responsible for the control of morphological changes in cell membrane organization, which are suggested to influence the signal transduction through the cell membrane walls. The model predictions are shown to be consistent with our previously reported experimental results. We numerically evaluated the range of possible scenarios of spatial pattern change and provide analytical expressions for SM-domain-area change rates and total dissolution times for several limiting cases. The model results suggest that it may be possible to tune the pattern changes by adjusting the relative importance of each of the three kinetic processes, which can be discriminated through experimentally measurable time-dependent SM concentration distributions or SM-domain-area variations with time.