Ultrafast diffusion of a fluorescent cholesterol analog in compartmentalized plasma membranes.
Bottom Line: Surprisingly, in the intact PM, Bdp-Chol diffused at the fastest rate ever found for any molecules in the PM, with a median diffusion coefficient (D) of 3.4 µm²/second, which was ∼10 times greater than that of non-raft phospholipid molecules (0.33 µm²/second), despite Bdp-Chol's probable association with raft domains.These results are consistent with the previously proposed model, in which the PM is compartmentalized by the actin-based membrane-skeleton fence and its associated transmembrane picket proteins for the macroscopic diffusion of all of the membrane molecules, and suggest that the probability of Bdp-Chol passing through the compartment boundaries, once it enters the boundary, is ∼10× greater than that of Cy3-DOPE.Since the compartment sizes are greater than those of the putative raft domains, we conclude that raft domains coexist with membrane-skeleton-induced compartments and are contained within them.
Affiliation: Institute for Integrated Cell-Material Sciences (WPI-iCeMS) and Institute for Frontier Medical Sciences, Kyoto University, Kyoto, 606-8507, Japan.Show MeSH
Mentions: After partial actin depolymerization by the latrunculin-B treatment, virtually all of the Cy3-PEs still exhibited simple-Brownian diffusion in the time scale of ≥1 second, with a ∼20% increase in DeffMACRO (Table3, the distribution for Cy3-DOPE is shown in Figure 10, bottom right), whereas actin stabilization by the jasplakinolide treatment led to a ∼35% decrease in DeffMACRO (the distribution for Cy3-DOPE is shown in Figure 10, bottom right) for all Cy3-PEs (means for Cy3-PEs, see Table3, which also includes the data obtained at 24°C). These results clearly indicate that the actin-based membrane skeleton, rather than the half-micron-sized domains that confine and concentrate saturated phospholipids proposed previously 36,37, is involved in slowing the phospholipid diffusion in the HASM-cell PM, strongly supporting that the actin-induced fence-picket model is applicable to the PM of the HASM cell.
Affiliation: Institute for Integrated Cell-Material Sciences (WPI-iCeMS) and Institute for Frontier Medical Sciences, Kyoto University, Kyoto, 606-8507, Japan.