title: Accumulation of anchored proteins forms membrane diffusion barriers during neuronal polarization.
abstract: The formation and maintenance of polarized distributions of membrane proteins in the cell membrane are key to the function of polarized cells. In polarized neurons, various membrane proteins are localized to the somatodendritic domain or the axon. Neurons control polarized delivery of membrane proteins to each domain, and in addition, they must also block diffusional mixing of proteins between these domains. However, the presence of a diffusion barrier in the cell membrane of the axonal initial segment (IS), which separates these two domains, has been controversial: it is difficult to conceive barrier mechanisms by which an even diffusion of phospholipids could be blocked. Here, by observing the dynamics of individual phospholipid molecules in the plasma membrane of developing hippocampal neurons in culture, we found that their diffusion was blocked in the IS membrane. We also found that the diffusion barrier is formed in neurons 7-10 days after birth through the accumulation of various transmembrane proteins that are anchored to the dense actin-based membrane skeleton meshes being formed under the IS membrane. We conclude that various membrane proteins anchored to the dense membrane skeleton function as rows of pickets, which even stop the overall diffusion of phospholipids, and may represent a universal mechanism for formation of diffusion barriers in the cell membrane.
authors.affiliation: Kusumi Membrane Organizer Project, Exploratory Research for Advancement of Technology Organization, JST, Nagoya 460-0012, Japan.
authors.forename: Chieko
authors.initials: C
authors.lastname: Nakada
authors.forename: Kenneth
authors.initials: K
authors.lastname: Ritchie
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Oba
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Nakamura
authors.forename: Yoko
authors.initials: Y
authors.lastname: Hotta
authors.forename: Ryota
authors.initials: R
authors.lastname: Iino
authors.forename: Rinshi S
authors.initials: RS
authors.lastname: Kasai
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Yamaguchi
authors.forename: Takahiro
authors.initials: T
authors.lastname: Fujiwara
authors.forename: Akihiro
authors.initials: A
authors.lastname: Kusumi
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000375:Aging / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000378:metabolism* / Q000648:ultrastructure; D016466:CHO Cells; D002454:Cell Differentiation / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism*; D016764:Cell Polarity / Q000502:physiology*; D006224:Cricetinae; D003712:Dendrites / Q000378:metabolism* / Q000648:ultrastructure; D004058:Diffusion; D006624:Hippocampus / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D008563:Membrane Lipids / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D008563:Membrane Lipids; D008565:Membrane Proteins; D010743:Phospholipids