Table 1.
Proteins involved in membrane sealing. See text for references.
| General function in membrane sealing | Protein name | Specific function | Site of action | |
|---|---|---|---|---|
| Sensing of membrane integrity | Sensing of Ca2+ influx into cytosol | PDCD6 | Binds to ALIX to promote ESCRT recruitment | Plasma membrane, endolysosomes |
| ALIX | Promotes ESCRT recruitment | Plasma membrane, endolysosomes | ||
| Annexins | Together with Ca2+ binding proteins of the S100 family, involved in membrane fusion, shaping, sealing and tension reduction | Plasma membrane, endolysosomes | ||
| SYT7 | Endolysosomal protein that activates SNAREs in membrane fusion | Plasma membrane | ||
| Dysferlin | Accumulates phosphatidylserine at the site of membrane damage, as an “eat‐me” signal for macrophages. Interacts with some annexins | Plasma membrane | ||
| TMEM16F | Lipid scramblase that causes exposure of phosphatidylserine at the extracytosolic leaflet | Plasma membrane | ||
| Sensing of β‐galactoside sugars on membrane proteins not normally exposed to cytosol | GAL3 | Interacts with ALIX and the autophagy‐associated ubiquitin E3 ligase TRIM16 | Endolysosomes | |
| GAL8 | Inhibits mTORC1 and interacts with the autophagy receptor NDP52 | Endolysosomes | ||
| GAL9 | Activates AMPK | Endolysosomes of macrophages and hematopoietic cells | ||
| Sensing of nuclear envelope integrity | CHMP7 | Binds to the inner nuclear membrane proteins LEMD2 and LEMD3 and recruits ESCRT‐III proteins | Nuclear envelope, micronuclear envelope | |
| Membrane fusion | SNARE proteins (VAMP, syntaxin and SNAP families) | Mediate fusion of specific membranes through formation of tetrahelical trans‐SNARE complexes | Multiple | |
| Membrane scission towards cytosol | Acidic sphingomyelinase | Lysosomal enzyme that is shed by Ca2+‐dependent exocytosis in response to wounding. Converts sphingomyelin into ceramide, which triggers caveolae endocytosis | Plasma membrane | |
| GRAF1 | GTPase‐activating protein for the small GTPase Cdc42. Promotes clathrin‐independent endocytosis | Plasma membrane, endosomes | ||
| Membrane scission away from cytosol | ESCRT‐I | Recruits ESCRT‐III | Multiple | |
| ESCRT‐III | Filamentous complex that mediates scission of narrow membrane necks filled with cytosol, to achieve membrane sealing | Multiple | ||
| VPS4 | AAA ATPase that regulates ESCRT‐III assembly and disassembly | Multiple | ||