The vault associates with membranes in situ

Area of Science:

• Cell Biology
• Structural Biology
• Biochemistry

Background:

• Eukaryotic vault particles are large ribonucleoprotein complexes with an unknown cellular function.
• Previous studies have extensively characterized vault structure but not their in situ distribution or interactions.

Purpose of the Study:

• To investigate the cellular distribution, structural states, and interaction partners of vault particles within intact cells.
• To elucidate the functional roles of vault particles by examining their localization and associations.

Main Methods:

• Cryo-electron tomography (cryo-ET) was used to visualize vault particles in Dictyostelium discoideum cells.
• Proximity labeling experiments were performed to identify vault particle interactors.

Main Results:

• A subpopulation of vault particles was found associated with endoplasmic reticulum (ER) and nuclear envelope membranes.
• These membrane-associated vaults localized to regions of altered membrane thickness and curvature.
• A fraction of vault particles were observed to enclose 80S ribosomes in ordered orientations.
• Proximity labeling identified ER-resident proteins and ribosomal components as vault interactors.

Conclusions:

• The discovery of membrane-bound and ribosome-encapsulating vault populations provides novel directions for research.
• These findings suggest potential roles for vaults in membrane dynamics and protein synthesis/processing.
• Future studies will focus on unraveling the precise functions of these newly identified vault populations.