Structural basis for VPS34 kinase activation by Rab1 and Rab5 on membranes

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Phosphatidylinositol-3-phosphate (PI3P) regulates crucial cellular processes like endocytosis and autophagy.
• PI3P is generated by two distinct VPS34-containing complexes: complex II on endosomes and complex I on autophagosomes.
• The activation mechanism of VPS34 by Rab GTPases, particularly Rab5 for complex II, remained unclear.

Purpose of the Study:

• To elucidate the mechanism by which Rab GTPases recruit and activate specific VPS34 complexes.
• To understand how Rab5a activates the endosomal VPS34 complex II.
• To investigate the interaction of Rab1a with the autophagosomal VPS34 complex I.

Main Methods:

• Utilized electron cryotomography to visualize complex II on Rab5a-decorated vesicles.
• Investigated Rab GTPase binding and activation of VPS34 complexes.
• Characterized the distinct binding interfaces and activation mechanisms for Rab5a and Rab1a.

Main Results:

• Rab5a-GTP recruits and activates endosomal VPS34 complex II by binding between VPS34 C2 and VPS15 WD40 domains.
• Electron cryotomography revealed VPS34 kinase domain release and readiness for catalysis upon Rab5a binding.
• Rab1a recruits and activates autophagy-specific VPS34 complex I, but not complex II.
• Both Rab proteins bind to the same VPS34 interface through unique interactions.

Conclusions:

• Specific Rab GTPases, Rab5a and Rab1a, differentially regulate VPS34 complexes.
• This Rab-mediated recruitment and activation mechanism ensures precise spatial and temporal control of PI3P production.
• The findings provide insight into the distinct cellular localization and activation of VPS34 complexes in endocytosis and autophagy.