Crystal structure of the Rab33B/Atg16L1 effector complex.

Area of Science:

• Cell Biology
• Molecular Biology
• Structural Biology

Background:

• The Atg12-Atg5/Atg16L1 complex is essential for autophagosome formation, recruited by WIPI2b.
• Atg16L1 functions as an effector for the Golgi-resident GTPase Rab33B.

Purpose of the Study:

• To determine the structural basis of the interaction between Rab33B and Atg16L1.
• To investigate the functional consequences of this interaction on autophagy and Golgi localization.

Main Methods:

• Co-expression and purification of murine Rab33B(30-202) Q92L and Atg16L1(153-210).
• X-ray crystallography to determine the structure of the Rab33B-Atg16L1 complex.
• Site-directed mutagenesis of interface residues.
• In vitro pull-down assays.
• Cellular co-localization studies.

Main Results:

• The crystal structure revealed two Rab33B molecules binding to the dimeric Atg16L1 coiled-coil domain.
• Mutagenesis studies confirmed the importance of interface residues for complex formation and cellular localization.
• Rab33B binding to Atg16L1 is necessary for Rab33B Golgi association.
• Atg16L1 mutants defective in Rab33B binding still co-localize with WIPI2b.

Conclusions:

• The study elucidates the structural mechanism of Rab33B-Atg16L1 interaction, critical for autophagosome biogenesis.
• The findings suggest that the proximity of Rab33B and WIPI2b binding sites on Atg16L1 facilitates lipid recruitment for autophagosomes.
• This work provides insights into the coordinated regulation of autophagy and Golgi function.