Small molecule allosteric modulators of phosphodiesterase 4

Area of Science:

• Biochemistry
• Structural Biology
• Drug Discovery

Background:

• Phosphodiesterase 4 (PDE4) inhibitors show clinical promise but are limited by side effects like emesis.
• Understanding PDE4 structure-activity relationships is crucial for developing better therapeutics.

Purpose of the Study:

• To elucidate novel PDE4 conformers for improved therapeutic agent design.
• To explore strategies for enhancing PDE4 inhibitor tolerability.

Main Methods:

• Cocrystallography of PDE4 catalytic units with regulatory domains and inhibitors.
• Analysis of distinct PDE4 conformational states (open, asymmetric dimer, symmetric dimer).

Main Results:

• Identified three distinct PDE4 conformers: open, asymmetric (trans-capping), and symmetric (cis-capping).
• Asymmetric conformer-targeting inhibitors partially inhibit PDE4, potentially improving tolerability by maintaining signaling patterns.
• Proposed role of accessory proteins in modulating PDE4 activity via regulatory helices.

Conclusions:

• Novel PDE4 conformers offer new avenues for designing potent and well-tolerated PDE4 inhibitors.
• Targeting specific PDE4 conformers, like the asymmetric dimer, may mitigate dose-limiting toxicities.
• Further research into accessory protein interactions could refine PDE4-targeted therapies.