title: Ultrafast diffusion of a fluorescent cholesterol analog in compartmentalized plasma membranes.
abstract: Cholesterol distribution and dynamics in the plasma membrane (PM) are poorly understood. The recent development of Bodipy488-conjugated cholesterol molecule (Bdp-Chol) allowed us to study cholesterol behavior in the PM, using single fluorescent-molecule imaging. 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. Furthermore, Bdp-Chol exhibited no sign of entrapment in time scales longer than 0.5 milliseconds. In the blebbed PM, where actin filaments were largely depleted, Bdp-Chol and Cy3-conjugated dioleoylphosphatidylethanolamine (Cy3-DOPE) diffused at comparable Ds (medians = 5.8 and 6.2 µm²/second, respectively), indicating that the actin-based membrane skeleton reduces the D of Bdp-Chol only by a factor of ∼2 from that in the blebbed PM, whereas it reduces the D of Cy3-DOPE by a factor of ∼20. 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.
authors: Institute for Integrated Cell-Material Sciences (WPI-iCeMS) and Institute for Frontier Medical Sciences, Kyoto University, Kyoto, 606-8507, Japan.
authors: Nao
authors: N
authors: Hiramoto-Yamaki
authors: Kenji A K
authors: KA
authors: Tanaka
authors: Kenichi G N
authors: KG
authors: Suzuki
authors: Koichiro M
authors: KM
authors: Hirosawa
authors: Manami S H
authors: MS
authors: Miyahara
authors: Ziya
authors: Z
authors: Kalay
authors: Koichiro
authors: K
authors: Tanaka
authors: Rinshi S
authors: RS
authors: Kasai
authors: Akihiro
authors: A
authors: Kusumi
authors: Takahiro K
authors: TK
authors: Fujiwara
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D001896:Boron Compounds; D002460:Cell Line; D002784:Cholesterol / Q000031:analogs & derivatives / Q000378:metabolism*; D004058:Diffusion; D005456:Fluorescent Dyes; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D010714:Phosphatidylethanolamines / Q000494:pharmacology; D051381:Rats
chemical_list: C410262:1,2-dioleoyl-glycero-3-phosphatidyl ethanolamine; C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D001896:Boron Compounds; D005456:Fluorescent Dyes; D010714:Phosphatidylethanolamines; D002784:Cholesterol
keywords: cholesterol; hop diffusion; phospholipids; raft domains; single fluorescent-molecule tracking; single-particle tracking