ESCRTfügg

ESCRTfügg, in Hungarian usage, refers to processes that depend on the ESCRT machinery to mediate membrane scission from the cytosolic side. The ESCRT system (endosomal sorting complex required for transport) comprises several protein complexes—ESCRT-0, -I, -II, -III—and the VPS4 ATPase. These components act in a coordinated sequence to recognize, sort, and remodel membranes, ultimately driving scission events that invert the usual topology of membrane cutting.

Mechanistically, ESCRT-0 and ESCRT-I recognize ubiquitinated cargo and help recruit ESCRT-II, which in turn engages ESCRT-III. ESCRT-III proteins assemble into filaments and polymers that constrict the membrane neck, allowing vesicle formation away from the cytosol, such as intralumenal vesicles within multivesicular bodies. After scission, VPS4, an AAA-ATPase, disassembles ESCRT-III complexes, resetting the system with the help of cofactors like Vta1.

Biological contexts in which ESCRT-dependent processes operate include the biogenesis of multivesicular bodies, the sorting of membrane proteins for degradation, the budding of many enveloped viruses, and the final abscission step of cytokinesis. ESCRT components also participate in other membrane remodeling events and may contribute to nuclear envelope and membrane repair processes in certain contexts.

Regulation and evolution: ESCRT pathways are regulated by adaptor proteins (such as TSG101 and ALIX) and by ubiquitin signals that influence cargo selection. The ESCRT machinery is conserved from archaea to eukaryotes, with modular complexity increasing in more complex organisms. Dysfunctions in ESCRT components have been associated with diseases and with altered viral replication and release in some pathogens.

Overall, ESCRTfügg captures the set of cellular processes that rely on this conserved membrane-remodeling toolkit to effect cytosol-to-extracellular or intra-organelle membrane scission.