The supramolecular architecture of junctional microdomains in native lens membranes

Buzhynskyy, Nikolay; Hite, Richard K; Walz, Thomas; Scheuring, Simon

doi:10.1038/sj.embor.7400858

Cited by 98 publications

(121 citation statements)

References 28 publications

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“…NATURE COMMUNICATIONS | DOI: 10.1038/ncomms3155 ARTICLE membranes by AFM [16][17][18] , they have not been observed on native cells in physiological buffer. Beyond structural aspects, questions remain unanswered concerning the dynamics of junctional microdomains, notably in the context of assuring cell adhesion during tissue deformation upon lens accommodation (focusing to different distances).…”

Section: Development Of Hybrid Hs-afm and Fluorescence Microscopementioning

confidence: 98%

“…For comparison, in conventional AFM setups, the impulse is about three orders of magnitude higher. We can identify AQP0 by the characteristic square array packing in lens cells, previously described by freeze fracture electron microscopy 15 and by AFM of isolated membranes [16][17][18] , with packing parameters of a ¼ b ¼ 6.5 nm, g ¼ 90° (Fig. 5a).…”

Section: Development Of Hybrid Hs-afm and Fluorescence Microscopementioning

confidence: 99%

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A hybrid high-speed atomic force–optical microscope for visualizing single membrane proteins on eukaryotic cells

et al. 2013

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High-speed atomic force microscopy is a powerful tool for studying structure and dynamics of proteins. So far, however, high-speed atomic force microscopy was restricted to well-controlled molecular systems of purified proteins. Here we integrate an optical microscopy path into high-speed atomic force microscopy, allowing bright field and fluorescence microscopy, without loss of high-speed atomic force microscopy performance. This hybrid high-speed atomic force microscopy/optical microscopy setup allows positioning of the high-speed atomic force microscopy tip with high spatial precision on an optically identified zone of interest on cells. We present movies at 960 ms per frame displaying aquaporin-0 array and single molecule dynamics in the plasma membrane of intact eye lens cells. This hybrid setup allows high-speed atomic force microscopy imaging on cells about 1,000 times faster than conventional atomic force microscopy/optical microscopy setups, and allows first time visualization of unlabelled membrane proteins on a eukaryotic cell under physiological conditions. This development advances high-speed atomic force microscopy from molecular to cell biology to analyse cellular processes at the membrane such as signalling, infection, transport and diffusion.

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Section: Development Of Hybrid Hs-afm and Fluorescence Microscopementioning

confidence: 98%

Section: Development Of Hybrid Hs-afm and Fluorescence Microscopementioning

confidence: 99%

A hybrid high-speed atomic force–optical microscope for visualizing single membrane proteins on eukaryotic cells

et al. 2013

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“…Recent x-ray and electron-diffraction structures have shown that AQP0 can exist both as a nonjunctional homotetramer (17), in which each monomer transports water, and as a junctional octamer formed by hydrophobic interactions between two tetramers juxtaposed headto-head in adjacent membranes (11,13,19,22). The conductance of the junctional form has been debated (11,17,19,20,22); it has been suggested that AQP0, in its junctional form, is nonconducting (11,19), but the differences between the structure of this form and that of the conducting, nonjunctional form seem minor (17). Junction formation has been associated with proteolytic cleavage of the C-terminus of AQP0 (11), but experimental evidence suggests that the cleaved form conducts water when not engaged in junction formation (23).…”

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confidence: 99%

Dynamic control of slow water transport by aquaporin 0: Implications for hydration and junction stability in the eye lens

Jensen

Dror

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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Aquaporin 0 (AQP0), the most abundant membrane protein in mammalian lens fiber cells, not only serves as the primary water channel in this tissue but also appears to mediate the formation of thin junctions between fiber cells. AQP0 is remarkably less water permeable than other aquaporins, but the structural basis and biological significance of this low permeability remain uncertain, as does the permeability of the protein in a reported junctional form. To address these issues, we performed molecular dynamics (MD) simulations of water transport through membrane-embedded AQP0 in both its (octameric) junctional and (tetrameric) nonjunctional forms. From our simulations, we measured an osmotic permeability for the nonjunctional form that agrees with experiment and found that the distinct dynamics of the conserved, lumen-protruding side chains of Tyr-23 and Tyr-149 modulate water passage, accounting for the slow permeation. The junctional and nonjunctional forms conducted water equivalently, in contrast to a previous suggestion based on static crystal structures that water conduction is lost on junction formation. Our analysis suggests that the low water permeability of AQP0 may help maintain the mechanical stability of the junction. We hypothesize that the structural features leading to low permeability may have evolved in part to allow AQP0 to form junctions that both conduct water and contribute to the organizational structure of the fiber cell tissue and microcirculation within it, as required to maintain transparency of the lens.membrane ͉ MD simulation ͉ water channel ͉ permeability ͉ cell adhesion

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“…By contrast, the AQP0 structure was determined to a resolution of 1.9 Å using 2D crystals produced by reconstituting delipidated protein with the synthetically made lipid dimyrostylphosphatidylcholine (DMPC). Since the double-layered 2D crystals have the same dimensions as AQP0-mediated membrane junctions between fiber cells in the lens [10], the synthetic DMPC lipid is likely to mimic the native lipids in the in vivo junctions [8]. The lipids in the 2D crystals form an almost complete bilayer and are sandwiched in between adjacent AQP0 tetramers.…”

Section: Introductionmentioning

confidence: 99%

Interactions of lipids with aquaporin-0 and other membrane proteins

Hite

Gonen

Walz

2007

Pflugers Arch - Eur J Physiol

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The structure of aquaporin-0 (AQP0) has recently been determined by electron crystallography of two-dimensional (2D) crystals and by x-ray crystallography of three-dimensional (3D) crystals. The electron crystallographic structure revealed nine lipids per AQP0 monomer, which form an almost complete bilayer. The lipids adopt a wide variety of conformations and tightly fill the space between adjacent AQP0 tetramers. The conformations of the lipid acyl chains appear to be determined not only by the protein surface but also by the acyl chains of adjacent lipid molecules. In the x-ray structure, the hydrophobic region of the protein is surrounded by a detergent micelle, with two ordered detergent molecules per AQP0 monomer. Despite the different environments, the electron crystallographic and x-ray structures of AQP0 are virtually identical, but they differ in the temperature factors of the atoms that either contact the lipids in the 2D crystals or are exposed to detergents in the 3D crystals. The temperature factors are higher in the x-ray structure, suggesting that the detergent-exposed AQP0 residues are less ordered than the corresponding ones contacting lipids in the 2D crystals. An examination of ordered detergent molecules in crystal structures of other aquaporins and of lipid molecules in 2D and 3D crystals of bacteriorhodopsin suggests that the increased conformational variability of detergent-exposed residues compared to lipid-contacting residues is a general feature.

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The supramolecular architecture of junctional microdomains in native lens membranes

Cited by 98 publications

References 28 publications

A hybrid high-speed atomic force–optical microscope for visualizing single membrane proteins on eukaryotic cells

A hybrid high-speed atomic force–optical microscope for visualizing single membrane proteins on eukaryotic cells

Dynamic control of slow water transport by aquaporin 0: Implications for hydration and junction stability in the eye lens

Interactions of lipids with aquaporin-0 and other membrane proteins

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