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Relaxation of Loaded ESCRT-III Spiral Springs Drives Membrane Deformation.

Chiaruttini N, Redondo-Morata L, Colom A, Humbert F, Lenz M, Scheuring S, Roux A - Cell (2015)

Bottom Line: We reasoned that Snf7 spirals could function as spiral springs.Furthermore, we observed that the elastic expansion of compressed Snf7 spirals generated an area difference between the two sides of the membrane and thus curvature.This spring-like activity underlies the driving force by which ESCRT-III could mediate membrane deformation and fission.

View Article: PubMed Central - PubMed

Affiliation: University of Geneva, Department of Biochemistry, quai Ernest Ansermet 30, 1211 Geneva 4, Switzerland.

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Related in: MedlinePlus

Modeling of Snf7 Patch Growth(A) A putative scenario for the nucleation and growth of Snf7 spirals into a patch: new spirals are formed from filaments protruding from pre-existing spirals. The new spirals separate from the mother spiral by filament break.(B) Schematic of the theoretical model for Snf7 patch growth. Snf7 spirals are represented by disks. Disks are created with an initial radius . Their area grows with a constant rate , which leads to a radius growing as the square root of time (upper graph and black curves). New spirals are nucleated over time proportionally to the spiral nucleation rate λ and to the total perimeter of existing disks.(C) Pictorial representations of a small membrane area being covered with Snf7 disks at the beginning (left) and at the end (right) of the growth process.(D) Cumulative distribution of spiral sizes (dots, calculated from Figure 2C) fitted with our theoretical model (line), imposing  = 25 nm. The single fit parameter  is equal to  μm3.
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fig3: Modeling of Snf7 Patch Growth(A) A putative scenario for the nucleation and growth of Snf7 spirals into a patch: new spirals are formed from filaments protruding from pre-existing spirals. The new spirals separate from the mother spiral by filament break.(B) Schematic of the theoretical model for Snf7 patch growth. Snf7 spirals are represented by disks. Disks are created with an initial radius . Their area grows with a constant rate , which leads to a radius growing as the square root of time (upper graph and black curves). New spirals are nucleated over time proportionally to the spiral nucleation rate λ and to the total perimeter of existing disks.(C) Pictorial representations of a small membrane area being covered with Snf7 disks at the beginning (left) and at the end (right) of the growth process.(D) Cumulative distribution of spiral sizes (dots, calculated from Figure 2C) fitted with our theoretical model (line), imposing  = 25 nm. The single fit parameter is equal to μm3.

Mentions: These observations prompted the question of how Snf7 patches were formed. Patch nucleation could, for instance, start from a single closed ring, like those seen by EM. It is conceivable that such rings could be prone to break open, thus freeing filament tips that could further grow into a spiral. How would then this initial spiral transform into a patch? A possible scenario consists of a two-step growth mechanism (Figure 3A). First, new spirals are nucleated in the vicinity of existing spirals (termed below spiral nucleation). Rupture of filaments would separate the newly formed spirals from the initial spiral. Second, these spirals would grow independently through the addition of monomers at their filament tips. This scenario accounts for the observed growth dynamics of Snf7 patches: the constant speed of the radial growth of the patches implies that the density of growing filament tips at their rim stays constant. The formation of new spirals generates new tips, maintaining a constant density of growing tips.


Relaxation of Loaded ESCRT-III Spiral Springs Drives Membrane Deformation.

Chiaruttini N, Redondo-Morata L, Colom A, Humbert F, Lenz M, Scheuring S, Roux A - Cell (2015)

Modeling of Snf7 Patch Growth(A) A putative scenario for the nucleation and growth of Snf7 spirals into a patch: new spirals are formed from filaments protruding from pre-existing spirals. The new spirals separate from the mother spiral by filament break.(B) Schematic of the theoretical model for Snf7 patch growth. Snf7 spirals are represented by disks. Disks are created with an initial radius . Their area grows with a constant rate , which leads to a radius growing as the square root of time (upper graph and black curves). New spirals are nucleated over time proportionally to the spiral nucleation rate λ and to the total perimeter of existing disks.(C) Pictorial representations of a small membrane area being covered with Snf7 disks at the beginning (left) and at the end (right) of the growth process.(D) Cumulative distribution of spiral sizes (dots, calculated from Figure 2C) fitted with our theoretical model (line), imposing  = 25 nm. The single fit parameter  is equal to  μm3.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4644223&req=5

fig3: Modeling of Snf7 Patch Growth(A) A putative scenario for the nucleation and growth of Snf7 spirals into a patch: new spirals are formed from filaments protruding from pre-existing spirals. The new spirals separate from the mother spiral by filament break.(B) Schematic of the theoretical model for Snf7 patch growth. Snf7 spirals are represented by disks. Disks are created with an initial radius . Their area grows with a constant rate , which leads to a radius growing as the square root of time (upper graph and black curves). New spirals are nucleated over time proportionally to the spiral nucleation rate λ and to the total perimeter of existing disks.(C) Pictorial representations of a small membrane area being covered with Snf7 disks at the beginning (left) and at the end (right) of the growth process.(D) Cumulative distribution of spiral sizes (dots, calculated from Figure 2C) fitted with our theoretical model (line), imposing  = 25 nm. The single fit parameter is equal to μm3.
Mentions: These observations prompted the question of how Snf7 patches were formed. Patch nucleation could, for instance, start from a single closed ring, like those seen by EM. It is conceivable that such rings could be prone to break open, thus freeing filament tips that could further grow into a spiral. How would then this initial spiral transform into a patch? A possible scenario consists of a two-step growth mechanism (Figure 3A). First, new spirals are nucleated in the vicinity of existing spirals (termed below spiral nucleation). Rupture of filaments would separate the newly formed spirals from the initial spiral. Second, these spirals would grow independently through the addition of monomers at their filament tips. This scenario accounts for the observed growth dynamics of Snf7 patches: the constant speed of the radial growth of the patches implies that the density of growing filament tips at their rim stays constant. The formation of new spirals generates new tips, maintaining a constant density of growing tips.

Bottom Line: We reasoned that Snf7 spirals could function as spiral springs.Furthermore, we observed that the elastic expansion of compressed Snf7 spirals generated an area difference between the two sides of the membrane and thus curvature.This spring-like activity underlies the driving force by which ESCRT-III could mediate membrane deformation and fission.

View Article: PubMed Central - PubMed

Affiliation: University of Geneva, Department of Biochemistry, quai Ernest Ansermet 30, 1211 Geneva 4, Switzerland.

Show MeSH
Related in: MedlinePlus