Biology subjects

Grishchuk, E.

Publications and source records attributed to Grishchuk, E..

4 recordsLinked to original sources

bioRxiv2026

Burst-like Secretion of Platelet Dense Granules Promotes Thrombus Shell Expansion

Vessel-wall injury triggers platelet recruitment and aggregation with exquisite spatiotemporal regulation. While secreted agonists from thrombin-activated platelets play a crucial role in thrombus formation, the underlying mechanisms remain elusive. Using real-time imaging of isolated human platelets, we demonstrate that dense granules, which are enriched with agonists, are released in brief, stochastic bursts driven by intracellular calcium spikes, which are necessary but not individually sufficient to trigger secretion events. This burst-like secretion is sustained through extracellular feedback, establishing a cooperative, probabilistic mechanism of granule release in which released agonists amplify thrombin-induced granule exocytosis and increase the likelihood of secretion bursts. Computational modeling of whole-thrombus growth reveals that these transient bursts generate localized microdomains of high agonist concentration, facilitating expansion of the outer thrombus layers. Our findings establish burst-like secretion as a distinct hemostatic mechanism that enhances platelet recruitment and orchestrates thrombus architecture through localized, self-reinforcing activation. Key pointsO_LILive imaging reveals dense granules secretion in discrete bursts. C_LIO_LIIntracellular calcium spikes are necessary but not sufficient for triggering secretion events. C_LIO_LIBurst-like secretion arises from cooperativity, driven by the feedback amplification from the extracellularly released granule content. C_LIO_LIBurst-like dense granule secretion promotes dynamic expansion of the thrombus shell in silico. C_LI

cell biology↗

bioRxiv2025

Ndc80 complex, a conserved coupler for kinetochore-microtubule motility, is a sliding molecular clutch

Chromosome motion at spindle microtubule plus-ends relies on dynamic molecular bonds between kinetochores and proximal microtubule walls. Under opposing forces, kinetochores move bi-directionally along these walls while remaining near the ends, yet how continuous wall-sliding occurs without end-detachment remains unclear. Using ultrafast force-clamp spectroscopy, we show that single Ndc80 complexes, the primary microtubule-binding kinetochore component, exhibit processive, bi-directional sliding. Plus-end-directed forces induce a mobile catch-bond in Ndc80, increasing frictional resistance and restricting sliding toward the tip. Conversely, forces pulling Ndc80 away from the plus-end trigger mobile slip-bond behavior, facilitating sliding. This dual behavior arises from force-dependent modulation of the Nuf2 calponin-homology domains microtubule binding, identifying this subunit as a friction regulator. We propose that Ndc80cs ability to modulate sliding friction provides the mechanistic basis for the kinetochores end coupling, enabling its slip-clutch behavior. One Sentence SummaryDirection-dependent mobile catch- and slip-bond behavior of the microtubule-binding Ndc80 protein

biophysics↗

bioRxiv2023

Higher-order assembly is a regulatory switch that promotes outer kinetochore recruitment

To faithfully segregate chromosomes during vertebrate mitosis, kinetochore-microtubule interactions must be restricted to a single site on each chromosome. Prior work on pair-wise kinetochore protein interactions has been unable to identify the mechanisms that prevent kinetochore formation in regions with a low density of CENP-A nucleosomes. To investigate the impact of higher-order assembly on kinetochore formation, we generated defined oligomers of the inner kinetochore protein CENP-T using two distinct, genetically engineered systems in human cells. Although individual CENP-T molecules interact poorly with other kinetochore proteins, oligomers that mimic the centromeric density of CENP-T trigger the robust formation of functional, cytoplasmic kinetochore-like particles. Both in cells and in vitro, each molecule of oligomerized CENP-T recruits substantially higher levels of outer kinetochore components than monomeric CENP-T molecules. Thus, the density-dependence of CENP-T restricts outer kinetochore recruitment to centromeres, where densely packed CENP-A recruits a high local concentration of CENP-T.

cell biology↗

bioRxiv2022

CLASP2 stabilizes GDP-associated terminal tubulins to prevent microtubule catastrophe

CLASPs are ubiquitous stabilizers of microtubule dynamics but their molecular targets at the microtubule plus-end are not understood. Using DNA origami-based reconstructions we show that clusters of human CLASP2 form a load-bearing bond with terminal GDP-tubulins at the stabilized microtubule tip. This activity relies on the unconventional TOG2 domain of CLASP2, which releases its high-affinity bond with the GDP-dimers upon their conversion into polymerization-competent GTP-tubulin. By tethering dynamic microtubule ends near immobilized CLASP2, we show that the targets for CLASP2 binding at the polymerizing tip arise stochastically, leading to nanoscale disruptions in microtubule tip integrity. The ability of CLASP2 to recognize nucleotide-specific tubulin conformation and stabilize the catastrophe-promoting GDP-tubulins intertwines with the previously underappreciated exchange between GDP and GTP at terminal tubulins, providing a distinct molecular mechanism to suppress microtubule catastrophe without affecting tubulin incorporation.

biophysics↗