Modelling the Full-Length Inactive PKC-δ Structure to Explore Regulatory Accessibility and Selective Targeting...

Area of Science:

• Biochemistry
• Structural Biology
• Cancer Biology

Background:

• Protein kinase C-δ (PKC-δ) is crucial in cell signaling and implicated in cancer development.
• The complete structure and interactions of PKC-δ are not well understood, hindering the development of targeted drugs.
• Understanding PKC-δ's inactive state is key for designing selective modulators.

Purpose of the Study:

• To determine the full-length inactive structure of PKC-δ.
• To identify accessible binding sites on PKC-δ for drug discovery.
• To provide a structural basis for PKC-δ regulation and modulation.

Main Methods:

• Generated a consensus structural model of inactive, full-length PKC-δ using comparative modeling.
• Employed molecular docking to predict ligands targeting the C2 domain.
• Validated ligand effects in breast cancer cell models, including those with C2 domain overexpression.

Main Results:

• The structural model elucidated the C2/V5 interdomain architecture and its role in regulating the nuclear localization signal (NLS).
• Two distinct ligand classes were identified: one binding to the C2 domain surface near the C2/V5 pocket, and another targeting the C2 domain phosphotyrosine-binding domain (PTD).
• Both ligands reduced cancer cell viability, with ligand 1 showing enhanced efficacy in C2-overexpressing cells and ligand 2 partially reversing C2 domain-induced effects.

Conclusions:

• Full-length structural information is vital for discovering functional binding sites and understanding context-dependent kinase regulation.
• Integrating computational modeling with experimental validation offers a pathway for selective PKC-δ modulation.
• This approach can guide drug discovery, enhance isoform selectivity, and inform strategies against kinase inhibitor resistance in oncology.