Distinct TRAPP complexes activate Ypt/Rab GTPases in secretion and autophagy

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Ypt/Rab GTPases are key regulators of intracellular transport.
• TRAPP complexes activate Ypt/Rab GTPases, but their specificities are debated.
• Ypt1/Rab1 and Ypt31/Rab11 are involved in secretion and autophagy.

Purpose of the Study:

• To determine the specificities of yeast TRAPP complexes in regulating Ypt/Rab GTPases.
• To elucidate the roles of TRAPPI, TRAPPII, and TRAPPIII in intracellular transport pathways.

Main Methods:

• In vivo analyses of mutations in yeast TRAPP complex subunits.
• Conditional depletion of essential TRAPPI and TRAPPIII subunits.
• Assessment of Golgi transport and protein localization.

Main Results:

• Deletion of Trs85 (TRAPPIII-specific) did not affect Golgi transport or Ypt1 localization.
• TRAPPI and TRAPPII are essential for early and late secretion steps, respectively.
• TRAPPI and TRAPPII activate Ypt1 and Ypt31 in early and late Golgi, respectively.
• TRAPPIII is implicated in Ypt1 activation specifically in autophagy.

Conclusions:

• TRAPPI and TRAPPII exhibit distinct specificities for Ypt/Rab activation in secretion.
• TRAPPIII's role is specific to Ypt1 activation during autophagy.
• This provides a mechanistic basis for the dual role of Ypt1/Rab1 in secretion and autophagy.