Biology subjects

Klingauf, J.

Publications and source records attributed to Klingauf, J..

3 recordsLinked to original sources

bioRxiv2022

Tetraspanner-based nanodomains modulate BAR domain-induced membrane curvature

Topography is a critical feature driving formation and dynamics of protein and lipid domains within biological membranes. The yeast plasma membrane (PM) has provided a powerful model system to study lateral domain formation, including characteristic BAR domain-induced PM furrows. Currently, it is not clear how the components involved in the establishment of these furrows cooperate to precisely regulate local PM topography. Here we report opposing functions for the Sur7 and Nce102 families of tetraspanner proteins in modulating membrane curvature and domain topography. Using STED nanoscopy and freeze-fracture EM we found that Sur7 tetraspanners form multimeric strands at the upper edges of PM furrows, which counteract the forces exerted by BAR domain proteins and prevent membrane tubulation. In contrast, Nce102 tetraspanners are located basal to the Sur7 proteins and promote BAR domain-induced curvature. The segregation of the two tetraspanner-based nanodomains is further supported by differential distribution of ergosterol to the upper edge of furrows and PIP2 lipids at the furrow base. These findings suggest a general role of tetraspanner proteins in sculpting local membrane domains.

cell biology↗

bioRxiv2022

Early endosomes act as local exocytosis hubs to repair endothelial membrane damage

The plasma membrane of a cell is subject to stresses causing ruptures that must be repaired immediately to preserve membrane integrity and ensure cell survival. Yet, the spatio-temporal membrane dynamics at the wound site and the source of membrane required for wound repair are poorly understood. Here, we show that early endosomes, previously only known to function in the uptake of extracellular material and its endocytic transport, are involved in plasma membrane repair in human endothelial cells. Using live-cell imaging and correlative light and electron microscopy, we demonstrate that membrane injury triggers a previously unknown exocytosis of early endosomes that is induced by Ca2+ entering through the wound. This exocytosis is restricted to the vicinity of the wound site and mediated by the endosomal SNARE VAMP2, which is crucial for efficient membrane repair. Thus, the here identified Ca2+-evoked and localized exocytosis of early endosomes supplies the membrane material required for rapid resealing of a damaged plasma membrane, thereby providing the first line of defense against damage in mechanically challenged endothelial cells.

cell biology↗

bioRxiv2022

Dynamic interplay of protrusive microtubule and contractile actomyosin forces drives tissue extension

In order to shape a tissue, cell-based mechanical forces have to be integrated into global force patterns. Over the last decades, the importance of actomyosin contractile arrays, which are the key constituents of various morphogenetic processes, has been established for many tissues. Intriguingly, recent studies demonstrate that the microtubule cytoskeleton mediates folding and elongation of the epithelial sheet during Drosophila morphogenesis, placing microtubule mechanics en par with actin-based processes. While these studies establish the importance of both cytoskeletal systems during cell and tissue rearrangements, a mechanistic explanation of their functional hierarchy is currently missing. Here, we dissect the individual roles of these two key generators of mechanical forces during epithelium elongation. We demonstrate that microtubules dictate cell shape changes and actomyosin refines them. Combining experimental and numerical approaches, we find that altering the microtubule and actomyosin functions results in predictable changes in tissue shape. We further show that planar polarized microtubule patterning is independent of cell geometry and actomyosin-based mechanics. These results support a hierarchical mechanism, whereby microtubule-based forces in some epithelial systems prime actomyosin-generated forces.

developmental biology↗