Vps41 functions as a molecular ruler for HOPS tethering complex-mediated membrane fusion

Area of Science:

• Cell biology
• Molecular biology
• Biochemistry

Background:

• Lysosomal fusion relies on the HOPS tethering complex.
• In yeast, HOPS links the Ypt7 GTPase to promote fusion via SNAREs.
• Vps41's extended alpha-solenoid domain connects Ypt7 interaction to the HOPS core.

Purpose of the Study:

• Investigate the role of Vps41's alpha-solenoid domain in HOPS function.
• Determine if solenoid length or architecture is critical for HOPS-mediated fusion.
• Elucidate the mechanism by which HOPS supports lysosomal fusion.

Main Methods:

• Genetic manipulation of the Vps41 alpha-solenoid domain length in yeast.
• Analysis of HOPS complex function in membrane tethering and fusion assays.
• Assessment of cellular phenotypes, including vacuolar morphology, endolysosomal sorting, and autophagy.

Main Results:

• Mutants with altered solenoid lengths tethered membranes but failed efficient fusion.
• Shortened solenoid mutants exhibited growth defects and impaired vacuolar morphology, endolysosomal sorting, and autophagy.
• Length-compensated mutants rescued these in vivo defects, indicating length is critical.

Conclusions:

• The precise length of Vps41's alpha-solenoid domain is essential for HOPS function in yeast.
• Solenoid architecture is dispensable, but length acts as a molecular ruler for HOPS-mediated fusion.
• This suggests a revised model for HOPS complex function in membrane fusion processes.