Biology subjects

Pust, S.

Publications and source records attributed to Pust, S..

4 recordsLinked to original sources

bioRxiv2026

Structure and function of the DFCP1 membrane barrier responsible for ER microdomain organization in lysosome repair

The endoplasmic reticulum (ER) forms specialized microdomains that organize autophagy, lipid droplet formation, and the repair of damaged lysosomes. The PI3P-binding protein DFCP1/ZFYVE1 marks these microdomains, raising the question as to whether and how one protein could define such a subcompartment. Here we determine the structure of full-length human DFCP1 bound to membranes by cryo-electron tomography and single-particle cryo-electron microscopy. DFCP1 assembles into a helical coat, built from tetramers that stack around a constricted membrane tube. Its ATPase domains form the organizing core of the helix, while its ER-targeting domains insert deeply into the outer leaflet, and its FYVE domains grip PI3P. Coarse-grained molecular dynamics simulations show that the coat does not simply follow the curvature of the membrane but acts as a barrier to lipid diffusion, almost completely blocking the movement of its cognate lipid PI3P past the filament and concentrating it beneath the coat. Point mutations that break the assembly, membrane-insertion or PI3P-binding interfaces each impair lysosomal repair in cells, and the assembly is also required for the focal recruitment of the lipid transporter VPS13C. We propose that DFCP1 collars fence off a specialized ER microdomain, so that locally made lipids can reach sites of repair rather than escaping into bulk ER.

cell biology↗

bioRxiv2026

The kinesin-4 family member KIF27 regulates mitotic progression, cytokinesis and genome stability

Kinesins are microtubule-dependent motors, yet the functions of the kinesin-4 family member KIF27 remain poorly understood. Here, we demonstrate a dynamic and cell-cycle-dependent localization of KIF27, consistent with its functional roles in mitotic progression. Upon mitotic entry, KIF27 relocates to condensed chromosomes. During anaphase, a fraction of KIF27 accumulates at the spindle midzone, and in telophase and late stages of cytokinesis it localizes at the midbody, colocalizing with key cytokinetic regulators at both structures. Recruitment of KIF27 to the midbody depends on KIF23 and CEP55. KIF27 depletion results in profound cell division defects, altered midbody and microtubule morphology, delayed cytokinesis and cytokinesis failure. Beyond cell division, KIF27 depletion directly compromises nuclear morphology, and pan-cancer transcriptomic analyses correlate low KIF27 expression with aneuploidy and poor patient survival in several cancer types. Together, our results identify KIF27 as a novel regulator of mitotic fidelity and genome stability.

Cell Biology↗

bioRxiv2022

Vesicle-mediated transport of ALIX and ESCRT-III to the intercellular bridge during cytokinesis

Cellular abscission is the final step of cytokinesis that leads to the physical separation of the two daughter cells. The scaffold protein ALIX and the ESCRT-I protein TSG101 contribute to recruiting ESCRT-III to the midbody, which orchestrates the final membrane scission of the intercellular bridge. Here, we addressed by which mechanisms ALIX and the ESCRT-III subunit CHMP4B are transported to the midbody. Structured illumination microscopy revealed gradual accumulation of ALIX at the midbody, resulting in the formation of spiral-like structures extending from the midbody to the abscission site, which strongly co-localized with CHMP4B. Live-cell microscopy uncovered that ALIX appeared together with CHMP4B in vesicular structures, whose motility was microtubule-dependent. Depletion of ALIX led to structural alterations of the midbody and delayed recruitment of CHMP4B, resulting in delayed abscission. Likewise, depletion of the kinesin-1 motor KIF5B reduced the motility of ALIX-positive vesicles and caused delayed recruitment of ALIX, TSG101 and CHMP4B to the midbody, accompanied by impeded abscission. We propose that ALIX, TSG101 and CHMP4B are associated with endosomal vesicles transported along microtubules by kinesin-1, leading to their directional transport to the cytokinetic bridge and midbody, thereby contributing to their function in abscission.

cell biology↗

bioRxiv2018

ERM proteins: The missing actin linkers in clathrin-mediated endocytosis

Canonical clathrin-coated pits (CCPs) are nucleated by the coordinated arrival of clathrin triskelia and AP2 adaptor proteins at phosphatidylinositol 4,5-bisphosphate (PIP2) enriched plasma membrane domains (1, 2). Subsequent propagation of the clathrin lattice helps to deform the membrane into a sharply curved pit (3). A large proportion of the initiated pits fall apart as abortive endocytic events within about 20 s, possibly due to insufficient cargo capture (4). Successful clathrin-mediated endocytosis (CME) is concluded when a clathrin-coated vesicle is released into the cell by dynamin-mediated fission of the CCP membrane neck (5, 6). A vast array of accessory proteins important for successful CME has been identified. Among these is actin, which has been shown to be required for the maturation and internalization of a subset of CCPs in human cells (7, 8). Actin dependency during CME correlates with elevated membrane tension, and CCP maturation requires actin polymerization during mitosis, in microvilli at the apical surface of polarized cells and in cells upon global mechanical stretching or hypotonic treatment (9-11). The Arp2/3 complex is thought to trigger an acute actin burst coinciding with CCP internalization, but how actin is recruited to CCPs in the first place is not known (12, 13). Here we show that the ERM (ezrin, radixin, moesin) protein family of membrane-actin linkers associates with CCPs, and that functional perturbation of ERM proteins impedes CCP maturation and reduces the rate of transferrin uptake. By total internal reflection fluorescence (TIRF) microscopy and unbiased object detection and tracking, we show that ezrin localizes to nascent CCPs and that these pits subsequently recruit actin. Based on these data, we propose a model in which activated ERM proteins recruit the initial actin filament during CME.

cell biology↗