Clustering of Raft-Associated Proteins in the External Membrane Leaflet Modulates Internal Leaflet H-Ras Diffusion and Signaling

摘要: One of the least-explored aspects cholesterol-enriched domains (rafts) in cells is coupling between such external and internal monolayers its potential to modulate transbilayer signal transduction. Here, we employed fluorescence recovery after photobleaching study effects antibody-mediated patching influenza hemagglutinin (HA) proteins [raft-resident wild-type HA glycosylphosphatidylinositol-anchored HA, or nonraft mutant HA(2A520)] on lateral diffusion internal-leaflet raft Ras isoforms (H-Ras K-Ras, respectively). Our studies demonstrate that clustering outer-leaflet transmembrane raft-associated (but not their mutants) retards H-Ras K-Ras), suggesting stabilized interactions with clusters proteins. These modulations were paralleled by specific activity but K-Ras. Thus, facilitated early step whereby converted an activated, GTP-loaded state inhibited ensuing downstream signaling via Mek/Erk pathway. We propose a model for modulation proteins, where (antibody ligand mediated) enhances association clusters, promoting either enhancement inhibition signaling.