Localization of Asgard archaeal ESCRT proteins to eukaryotic cellular structures

Area of Science:

• Cell Biology
• Evolutionary Biology
• Biochemistry

Background:

• Eukaryotic internal membrane systems arose during eukaryogenesis, but the adaptation of pre-eukaryotic proteins remains poorly understood.
• Asgard archaea, the closest prokaryotic relatives to eukaryotes, possess homologs of Endosomal Sorting Complex Required for Transport (ESCRT) proteins, crucial for membrane remodeling in eukaryotes.

Purpose of the Study:

• To investigate the function and localization of ESCRT homologs from the Asgard archaeon *Promethearchaeum syntrophicum* (MK-D1) in a eukaryotic context.
• To explore the evolutionary origins of ESCRT-mediated membrane remodeling and its role in eukaryogenesis.

Main Methods:

• Expression of ESCRT-II and ESCRT-III homologs, VSP4 and ubiquitin, from *P. syntrophicum* (MK-D1) in human cells.
• Analysis of the localization patterns of these archaeal proteins within human cells using microscopy.

Main Results:

• Archaeal ESCRT proteins (VSP4 and ubiquitin) were recruited to specific structures when expressed in human cells.
• These proteins localized to canonical eukaryotic ESCRT recruitment sites, including midbodies and centrosomes, despite these structures being absent in MK-D1.
• This conserved localization indicates molecular interactions predating eukaryotic internal membranes and cellular structures.

Conclusions:

• The findings support a model where ancestral protein machines were repurposed during eukaryogenesis.
• This repurposing facilitated the integration of existing ESCRT functions and networks into new cellular architectures, contributing to eukaryotic complexity.