AP-3 vesicle uncoating occurs after HOPS-dependent vacuole tethering

Area of Science:

• Cell biology
• Molecular and cell biology
• Membrane trafficking

Background:

• Adapter protein (AP) complexes are crucial for vesicle formation and cargo selection at endomembranes.
• AP-3 vesicles, involved in Golgi-to-vacuole transport, were thought to require Vps41 and potentially clathrin for their formation.
• The HOPS complex, containing Vps41, tethers AP-3 vesicles to vacuoles.

Purpose of the Study:

• To investigate the role of Vps41 in AP-3 vesicle formation and tethering.
• To determine if clathrin is essential for AP-3 vesicle budding.
• To elucidate the mechanism of AP-3 vesicle uncoating.

Main Methods:

• Anchoring Vps41 to the mitochondrial outer membrane to study AP-3 recruitment.
• Monitoring AP-3 vesicle formation and recruitment in the absence of Vps41 or clathrin.
• Employing proximity labeling and mass spectrometry to identify interacting proteins.

Main Results:

• Vps41 can tether AP-3 vesicles to mitochondria, but AP-3 vesicles can form independently of Vps41 or clathrin.
• The Arf1 GTPase-activating protein (GAP) Age2 was identified as part of the AP-3 coat.
• Vesicle tethering can occur before complete coat uncoating.

Conclusions:

• AP-3 vesicle formation does not require Vps41 or clathrin.
• AP-3 vesicles maintain their coat after budding and only fully uncoat after tethering at the vacuole.
• Age2 is a component of the AP-3 coat involved in vesicle trafficking.