GTP hydrolysis triggers membrane remodeling by AMPH-1

Area of Science:

• Cell Biology
• Molecular Biology
• Membrane Trafficking

Background:

• Membrane-enclosed transport carriers mediate molecular return from recycling endosomes to the plasma membrane.
• The precise mechanism of carrier formation remains incompletely understood.
• In Caenorhabditis elegans, amphiphysin (AMPH-1) is essential for carrier biogenesis from recycling endosomes.

Purpose of the Study:

• To elucidate the molecular mechanism by which AMPH-1 facilitates transport carrier formation.
• To propose and test a model linking guanine nucleotide binding and hydrolysis to AMPH-1's membrane remodeling functions.
• To understand the role of AMPH-1's structural dynamics in membrane tubulation and vesiculation.

Main Methods:

• Biochemical assays using purified AMPH-1 and liposomes.
• Investigation of AMPH-1's interaction with membranes in different guanine nucleotide-bound states (GTP vs. GDP).
• Structural analysis of AMPH-1's role in membrane tubulation and oligomerization.

Main Results:

• Purified AMPH-1 alone can induce tubulation and vesiculation of liposomes.
• Guanine nucleotide binding regulates AMPH-1's membrane association and structural transitions.
• GTP binding stabilizes AMPH-1-membrane interactions via N-terminal amphipathic helices.
• GDP-bound AMPH-1 forms an oligomeric lattice that tubulates membranes, preceding fission.

Conclusions:

• A model is proposed where GTP binding and hydrolysis drive AMPH-1-mediated membrane remodeling for carrier formation.
• AMPH-1's conformational changes, regulated by guanine nucleotides, are critical for organizing membrane structures necessary for transport.
• This study provides mechanistic insights into the role of amphiphysins in endosomal recycling and membrane trafficking.