A hydrodynamic instability drives protein droplet formation on microtubules to nucleate branches

Setru, Sagar; Gouveia, Bernardo; Alfaro-Aco, Raymundo; Shaevitz, Joshua W.; Stone, Howard A.; Petry, Sabine

doi:10.1038/s41567-020-01141-8

Cited by 72 publications

(54 citation statements)

References 50 publications

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“…Recently a number of microtubule associated proteins (MAPs) have been reported to undergo similar demixing in vitro with proposed relevance for microtubule dynamics, nucleation, branching etc. (Hernández-Vega et al, 2017; King and Petry, 2020; Setru et al, 2021; Siahaan et al, 2019; Tan et al, 2019). While the importance of these liquid- and gel-like assemblies for cellular function is still controversial (Alberti et al, 2019; McSwiggen et al, 2019; Raff, 2019), it is widely accepted that disordered protein regions often drive interactions leading to phase separation (Wang et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Multivalent interactions facilitate motor-dependent protein accumulation at growing microtubule plus ends

Maan

Reese

Volkov

et al. 2021

Preprint

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Growing microtubule ends provide platforms for the accumulation of plus-end tracking proteins that organize into comets of mixed protein composition. Using a reconstituted fission yeast system consisting of end-binding protein Mal3, kinesin Tea2 and cargo Tip1, we found that these proteins can be driven into liquid phase droplets both in solution and at microtubule ends under crowding conditions. In the absence of crowding agents, cryo-electron tomography revealed that motor-dependent comets consist of disordered networks where multivalent interactions appear to facilitate the non-stoichiometric accumulation of cargo Tip1. We dissected the contribution of two disordered protein regions in Mal3 and found that both are required for the ability to form droplets and Tip1 accumulation, while autonomous Mal3 comet formation only requires one of them. Using theoretical modeling, we explore possible mechanisms by which motor activity and multivalent interactions may lead to the observed enrichment of Tip1 at microtubule ends.

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Section: Introductionmentioning

confidence: 99%

Multivalent interactions facilitate motor-dependent protein accumulation at growing microtubule plus ends

Maan

Reese

Volkov

et al. 2021

Preprint

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“…Surface partitioning could contribute to the observed core-shell structure of stress granules [9]. Wetting interactions of protein droplets with microtubules have been shown to facilitate branching [54,55]. Because of their non-specific nature, we expect that interfacial forces could play a role in a number of interactions of membrane-less organelles with other supra-molecular structures.…”

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confidence: 99%

Non-specific adhesive forces between filaments and membraneless organelles

Böddeker

Rosowski

Berchtold

et al. 2021

Preprint

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Membraneless organelles are liquid-like domains that form inside living cells by phase-separation. While standard physical models of their formation assume their surroundings to be a simple liquid, the cytoplasm is an active viscoelastic environment. To investigate potential coupling of phase separation with the cytoskeleton, we quantify structural correlations of stress granules and microtubules in a human-derived epithelial cell line. We find that microtubule networks are significantly perturbed in the vicinity of stress granules, and that large stress granules conform to the local pore-structure of the microtubule network. When microtubules are depolymerized by nocodazole, tubulin enrichment is localized near the surface of stress granules. We interpret these data using a thermodynamic model of partitioning of particles to the surface and bulk of droplets. This analysis shows that proteins generically have a non-specific affinity for droplet interfaces, which becomes most apparent when they weakly partition to the bulk of droplets and have a large molecular weight. In this framework, our data is consistent with a weak (lower than kbT) affinity of tubulin sub-units for stress granule interfaces. As microtubules polymerize their affinity for interfaces increases, providing sufficient adhesion to deform droplets and/or the network. We validate this basic physical phenomena in vitro through the interaction of a simple protein-RNA condensate with tubulin and microtubules.

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“…During autophagy, surface tension determines whether p62 condensates will be sequestered in small droplets or digested as a whole 15 . Finally, the nucleation of microtubule branches relies on an instability of TPX2 condensates, driven solely by the condensates’ surface tension 16 .…”

Section: Main Textmentioning

confidence: 99%

“…Many proteins tend to wet and adsorb onto solid surfaces 4,16,23,24,34 . While potentially mediating important biological processes 15,16,34 , this wetting effect can introduce significant artifacts in measurements that rely on the fusion kinetics or morphology of condensates 12,23,24 . In contrast, the contribution of R c in eq.…”

Section: Main Textmentioning

confidence: 99%

More than just oil droplets in water: surface tension and viscosity of protein condensates quantified by micropipette aspiration

Wang

Milovanović

et al. 2021

Preprint

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The material properties of biomolecular condensates play pivotal roles in many biological and pathological processes. Despite the rapid increase in the number of biomolecules identified that undergo liquid-liquid phase separation (LLPS), quantitative studies of the resulting condensates have been severely lagging behind. Here, we develop a micropipette-based technique, which uniquely allows quantifications of both the surface tension and viscosity of biomolecular condensates, independent of labeling and surface wetting effects. We demonstrate the accuracy and versatility of this technique by measuring condensates of LAF-1 RGG domains and a polymer-based aqueous two-phase system (ATPS). We anticipate this technique will be widely applicable to biomolecular condensates and will resolve several limitations regarding current approaches.

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A hydrodynamic instability drives protein droplet formation on microtubules to nucleate branches

Cited by 72 publications

References 50 publications

Multivalent interactions facilitate motor-dependent protein accumulation at growing microtubule plus ends

Multivalent interactions facilitate motor-dependent protein accumulation at growing microtubule plus ends

Non-specific adhesive forces between filaments and membraneless organelles

More than just oil droplets in water: surface tension and viscosity of protein condensates quantified by micropipette aspiration

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