Determinants of endocytic membrane geometry, stability, and scission

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Endocytic vesicle formation involves protein-mediated membrane bending and scission.
• Bin-Amphiphysin-Rvs (BAR) and Fer-CIP4 homology-BAR (F-BAR) proteins are implicated in membrane curvature and endocytosis.
• F-BAR proteins Syp1 and Bzz1 are present at yeast endocytic sites, with Syp1 departing before deep invagination.

Purpose of the Study:

• To elucidate the mechanisms and protein cooperation driving membrane scission during yeast endocytosis.
• To investigate the roles of Bzz1, Rvs161/167, actin polymerization, and Sjl2 in membrane shaping and scission.
• To understand how these factors contribute to the formation of deep membrane invaginations and efficient scission.

Main Methods:

• Genetic analyses to study protein function and interactions.
• Spatiotemporal analysis to track protein localization and dynamic events.
• Ultrastructural analysis to examine membrane morphology at high resolution.

Main Results:

• Bzz1, heterodimeric BAR domain protein Rvs161/167, actin polymerization, and lipid phosphatase Sjl2 cooperate to induce membrane scission.
• Actin assembly and Rvs161/167 drive the formation of deep membrane invaginations.
• Bzz1 stabilizes endocytic sites, while Bzz1 and Rvs161/167 together establish proper membrane geometry for efficient scission.

Conclusions:

• A dynamic interplay between a lipid phosphatase, actin assembly, and membrane-sculpting proteins (Bzz1, Rvs161/167) is essential for endocytic membrane shaping, tubule stabilization, and scission.
• Distinct mechanisms employed by these factors contribute to the precise geometric changes required for efficient vesicle formation.
• The findings reveal a coordinated molecular mechanism underlying membrane scission in yeast endocytosis.