title: Confined diffusion of transmembrane proteins and lipids induced by the same actin meshwork lining the plasma membrane.
abstract: The mechanisms by which the diffusion rate in the plasma membrane (PM) is regulated remain unresolved, despite their importance in spatially regulating the reaction rates in the PM. Proposed models include entrapment in nanoscale noncontiguous domains found in PtK2 cells, slow diffusion due to crowding, and actin-induced compartmentalization. Here, by applying single-particle tracking at high time resolutions, mainly to the PtK2-cell PM, we found confined diffusion plus hop movements (termed "hop diffusion") for both a nonraft phospholipid and a transmembrane protein, transferrin receptor, and equal compartment sizes for these two molecules in all five of the cell lines used here (actual sizes were cell dependent), even after treatment with actin-modulating drugs. The cross-section size and the cytoplasmic domain size both affected the hop frequency. Electron tomography identified the actin-based membrane skeleton (MSK) located within 8.8 nm from the PM cytoplasmic surface of PtK2 cells and demonstrated that the MSK mesh size was the same as the compartment size for PM molecular diffusion. The extracellular matrix and extracellular domains of membrane proteins were not involved in hop diffusion. These results support a model of anchored TM-protein pickets lining actin-based MSK as a major mechanism for regulating diffusion.
authors: Center for Meso-Bio Single-Molecule Imaging, Institute for Integrated Cell-Material Sciences, Kyoto 606-8501, Japan.
authors: Takahiro K
authors: TK
authors: Fujiwara
authors: Institute for Frontier Medical Sciences, Kyoto University, Kyoto 606-8507, Japan.
authors: Kokoro
authors: K
authors: Iwasawa
authors: Institute for Integrated Cell-Material Sciences, Kyoto 606-8507, Japan.
authors: Ziya
authors: Z
authors: Kalay
authors: Institute for Integrated Cell-Material Sciences, Kyoto 606-8507, Japan.
authors: Taka A
authors: TA
authors: Tsunoyama
authors: Institute for Integrated Cell-Material Sciences, Kyoto 606-8507, Japan.
authors: Yusuke
authors: Y
authors: Watanabe
authors: Department of Physiology and Systems Bioscience, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.
authors: Yasuhiro M
authors: YM
authors: Umemura
authors: National Institute for Physiological Sciences, Okazaki 444-8585, Japan.
authors: Hideji
authors: H
authors: Murakoshi
authors: Institute for Integrated Cell-Material Sciences, Kyoto 606-8507, Japan Institute for Stem Cell Biology and Regenerative Medicine and National Centre for Biological Sciences, Bangalore 650056, India.
authors: Kenichi G N
authors: KG
authors: Suzuki
authors: Institute for Integrated Cell-Material Sciences, Kyoto 606-8507, Japan.
authors: Yuri L
authors: YL
authors: Nemoto
authors: MRC Toxicology Unit, University of Leicester, Leicester LE1 9HN, United Kingdom.
authors: Nobuhiro
authors: N
authors: Morone
authors: Institute for Frontier Medical Sciences, Kyoto University, Kyoto 606-8507, Japan Institute for Integrated Cell-Material Sciences, Kyoto 606-8507, Japan Membrane Cooperativity Unit, Okinawa Institute of Science and Technology, Onna-son, Okinawa 904-0412, Japan akusumi@frontier.kyoto-u.ac.jp.
authors: Akihiro
authors: A
authors: Kusumi
mesh_terms: D008841:Actin Cytoskeleton; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D004058:Diffusion; D006801:Humans; D008954:Models, Biological; D010743:Phospholipids / Q000737:chemistry*; D048328:Potoroidae; D051381:Rats; D011990:Receptors, Transferrin / Q000737:chemistry*
chemical_list: D010743:Phospholipids; D011990:Receptors, Transferrin