An Engineered Minimal WASP-Myosin Fusion Protein Reveals Essential Functions for Endocytosis

Area of Science:

• Cell biology
• Molecular and cell biology
• Biochemistry

Background:

• Actin polymerization drives membrane deformation critical for cellular processes like clathrin-mediated endocytosis (CME).
• In yeast, CME involves a six-protein complex coordinating actin polymerization, including WASP and class I myosins.
• Understanding the minimal requirements for this complex is key to elucidating CME mechanisms.

Purpose of the Study:

• To determine if a single engineered protein can substitute for the native six-protein WASP/Myosin complex in yeast CME.
• To identify the essential activities of the WASP/Myosin complex required for driving membrane invagination during CME.

Main Methods:

• Protein engineering to create a single fusion protein combining essential domains.
• Yeast genetics and live-cell imaging to assess the functional capacity of the engineered protein in CME.

Main Results:

• A single engineered protein successfully replaced the native six-protein complex, supporting CME.
• The engineered protein demonstrated four critical activities: recruitment, membrane anchorage, Arp2/3 activation, and motor domain actin binding.
• Myosin-mediated coupling between the plasma membrane and actin filaments was identified as essential for actin-driven membrane invagination.

Conclusions:

• The WASP/Myosin complex's functions can be consolidated into a single protein, simplifying the machinery for CME.
• Myosin's role in coupling actin filaments to the membrane base is crucial for efficient actin polymerization to drive CME.
• This study provides insights into the fundamental biophysical requirements for actin-based membrane remodeling.