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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 the membrane required for wound repair are poorly understood. Here, it is shown 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, it is demonstrated 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 soluble N‐ethylmaleimide sensitive factor attachment protein receptor (SNARE) VAMP2, which is crucial for efficient membrane repair. Thus, the newly 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. [ABSTRACT FROM AUTHOR]

During virus entry, members of the Polyomaviridae transit the endolysosomal network en route to the endoplasmic reticulum (ER), from which degraded capsids escape into the cytoplasm and enter the nucleus. Emerging evidence suggests that viruses require both endosomal acidification and the correct ionic balance of K+ and Ca2+ ions in endosomes for correct virus trafficking and genome release. Here, using two polyomaviruses with different capsid architectures, namely Simian virus 40 (SV40) and Merkel cell polyomavirus (MCPyV), we describe methods to rapidly quantify virus infection using IncuCyte ZOOM imaging analysis, and use this system to investigate the role of both K+ and Ca2+ channels during the early stages of virus entry. Using broad spectrum blockers of both K+ and Ca2+ channels to specifically target host cell ion channel functionality, we show that MCPyV, but not SV40 can be inhibited by K+ channel modulators, whilst both viruses are restricted by the broad spectrum Ca2+ channel inhibitor verapamil. Using a panel of more specific Ca2+ blockers, we show that both MCPyV and SV40 are dependent on the activity of two-pore Ca2+ channels (TPCs), as the TPC-specific blocker tetrandrine prevented capsid disassembly and nuclear transport required for virus entry. We therefore reveal a novel target to restrict the entry of polyomaviruses, which given the known role of TPCs during endolysosomal-ER fusion, is likely to be applicable to other viruses that transit this pathway. • We describe novel high-throughput assays to study SV40 and MCPyV infection. • MCPyV, but not SV40, is sensitive to K+ channel inhibition. • Verapamil inhibits MCPyV and SV40 infection. • Tetrandrine is a potent inhibitor of MCPyV and SV40 infection. • Two-pore channel 1/2 activity is essential for polyomavirus entry. [ABSTRACT FROM AUTHOR]