Phase separation modulates the functional amyloid assembly of human CPEB3

Area of Science:

• Neuroscience
• Biochemistry
• Molecular Biology

Background:

• Functional amyloids play roles in cellular processes, but their regulation is unclear.
• Cytoplasmic polyadenylation element-binding protein 3 (CPEB3) forms functional amyloids essential for memory persistence.
• CPEB3's monomeric state represses translation, while its aggregated state activates it.

Purpose of the Study:

• To investigate the sequence-driven molecular determinants of human CPEB3 (hCPEB3) functional aggregation.
• To understand how hCPEB3 transitions between functional states.

Main Methods:

• Analysis of intrinsically disordered regions (IDRs) in hCPEB3.
• Investigating hydrophobic interactions and ionic strength dependence in phase separation.
• Observing droplet aging and liquid-to-solid transitions.
• Examining protein behavior under physiological-like conditions.

Main Results:

• The hCPEB3 IDR contains both amyloidogenic and phase separation domains.
• hCPEB3's amyloid core is hydrophobic, unlike its Drosophila ortholog's Q-rich region.
• hCPEB3 undergoes liquid-to-solid transition forming hydrogels, with phase separation dependent on hydrophobic interactions and ionic strength.
• Physiological conditions promote electrostatic interactions, stabilizing liquid droplets and driving condensation-based amyloid formation.

Conclusions:

• hCPEB3 aggregation is governed by specific sequence elements and environmental factors.
• The protein's unique hydrophobic amyloid core and condensation pathway are key to its function.
• Environmental cues modulate hCPEB3's phase separation and amyloid formation, impacting its role in synaptic plasticity.