Multiscale Analysis of PNPLA2 and PNPLA3 Membrane Targeting

Area of Science:

• Biochemistry
• Cell Biology
• Structural Biology

Background:

• Lipid droplets (LDs) are crucial for cellular lipid homeostasis, regulated by associated proteins.
• Patatin-like phospholipase domain-containing proteins PNPLA2 (ATGL) and PNPLA3 are key regulators of lipid metabolism.
• The precise mechanisms of PNPLA2 and PNPLA3 membrane targeting and enzymatic regulation are not fully understood.

Purpose of the Study:

• To investigate the molecular mechanisms of PNPLA2 and PNPLA3 association with endoplasmic reticulum (ER) and LD membranes.
• To elucidate how distinct membrane-binding modes influence the enzymatic activities of PNPLA2 and PNPLA3.
• To understand the role of membrane composition in modulating these protein-membrane interactions.

Main Methods:

• Coarse-grained and all-atom molecular dynamics simulations with enhanced sampling.
• Computational modeling of protein-membrane interactions.
• Fluorescence microscopy experiments to validate computational predictions.

Main Results:

• PNPLA2 and PNPLA3 exhibit distinct membrane-binding modes, driven by divergent C-terminal amphipathic helices, despite a shared patatin domain.
• PNPLA2 forms a U-shaped helical bundle on LDs, inducing membrane curvature and promoting catalytic activity.
• PNPLA3 displays a flexible helical arrangement, maintaining a compact catalytic geometry and limiting substrate access; membrane composition modulates these interactions.

Conclusions:

• Distinct membrane-binding modes of PNPLA2 and PNPLA3 are mechanistically linked to their catalytic regulation and function.
• Lipid environments dynamically tune the activity of LD-associated enzymes.
• Understanding these interactions provides molecular insights into lipid metabolism regulation.