The ESCRTs - converging on mechanism.

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Endosomal sorting complexes required for transport (ESCRTs) are crucial protein machineries involved in diverse cellular membrane remodeling events.
• ESCRTs mediate 'reverse-topology' membrane scission, acting internally on membrane necks during processes like viral budding and membrane repair.
• The intricate nature and unusual mechanism of ESCRT action have presented significant research challenges.

Purpose of the Study:

• To review recent advances in understanding ESCRT function, particularly focusing on structural, in vitro, and in silico mechanistic studies.
• To synthesize current knowledge and highlight the emerging consensus on the ESCRT-mediated membrane scission mechanism.
• To place these mechanistic insights within their broader biological context.

Main Methods:

• Structural analysis of ESCRT complexes and their assemblies.
• In vitro reconstitution assays to study ESCRT protein function and dynamics.
• In silico mechanistic studies to model ESCRT-driven membrane scission.

Main Results:

• Recent structural studies reveal that ESCRT-I can form helical structures, complementing known ESCRT-III filament geometries.
• Mechanistic studies suggest a model driven by progressive ATP-dependent treadmilling and exchange of ESCRT subunits.
• ESCRT filament composition and geometry undergo dynamic changes during membrane scission.

Conclusions:

• The field is converging on a model for ESCRT-mediated membrane scission involving dynamic filament rearrangements.
• ATP-dependent subunit exchange is a key driver of ESCRT filament progression and function.
• Understanding ESCRT mechanisms provides insight into fundamental cellular processes like viral egress and membrane repair.