Myosin-V is activated by binding secretory cargo and released in coordination with Rab/exocyst function

Area of Science:

• Cell Biology
• Molecular Motors
• Cytoskeletal Dynamics

Background:

• Cellular organization relies on motor proteins transporting cargo along cytoskeletal tracks.
• The precise coordination of cargo delivery cycles with cellular events remains incompletely understood.

Purpose of the Study:

• To elucidate the in vivo delivery cycle of myosin-V, a key motor protein for secretory vesicle transport in yeast.
• To investigate the regulatory mechanisms governing myosin-V activation and release during vesicle transport.

Main Methods:

• In vivo studies utilizing yeast as a model organism.
• Genetic manipulation of myosin-V to assess vesicle binding and motor activity.
• Analysis of secretory vesicle transport dynamics and motor protein association.

Main Results:

• Myosin-V activation is triggered by secretory vesicle binding; impaired binding leads to constitutive motor activity.
• Approximately ten myosin-V motors per vesicle facilitate rapid transport to growth sites.
• Motor release is regulated by vesicle-bound Rab-GTP hydrolysis and exocyst-mediated tethering, independent of membrane fusion.

Conclusions:

• The study defines a complete in vivo myosin-V secretory vesicle transport cycle in yeast.
• Key regulatory steps involve motor activation by cargo binding and temporally controlled release.
• Conserved components suggest broad applicability to myosin-V-mediated transport in other organisms, including vertebrates.