H-ras, K-ras, and inner plasma membrane raft proteins operate in nanoclusters with differential dependence on the actin cytoskeleton.

摘要: Plasma membrane compartmentalization imposes lateral segregation on proteins that is important for regulating signal transduction. We use computational modeling of immunogold spatial point patterns intact plasma sheets to test different models inner organization. find at the nanoscale level but show a classical raft model preexisting stable domains into which lipid partition incompatible with generated by labeling palmitoylated marker protein. Rather, ≈30% protein exists in cholesterol-dependent nanoclusters, ≈70% distributed as monomers. The cluster/monomer ratio (number clusters/number outside clusters) independent expression level. H-rasG12V and K-rasG12V also operate nanoclusters fixed ratios are Detailed calibration imaging protocol suggests radii RasG12V may be small 11 6 nm, respectively, shows contain numbers (6.0-7.7) proteins. Raft do not form if actin cytoskeleton disassembled. formation actin-dependent. signaling abrogated disassembly, nanoclustering critical Ras function. These findings argue against favor dynamic actively regulated similar those proposed outer membrane. facilitate assembly essential transduction complexes.