Small-Molecule FICD Inhibitors Suppress Endogenous and Pathologic FICD-Mediated Protein AMPylation

Area of Science:

• Biochemistry
• Molecular Biology
• Cellular Stress Response

Background:

• The enzyme FICD (phosphocholine transferase) regulates endoplasmic reticulum (ER) stress by modifying the BiP/GRP78 chaperone.
• Dysregulated BiP/GRP78 AMPylation is implicated in various human diseases, yet specific inhibitors are unavailable.
• FICD's bifunctional activity, catalyzing both AMP addition and removal, presents a complex therapeutic challenge.

Purpose of the Study:

• To identify and validate small molecules that inhibit the pathogenic activity of FICD.
• To explore the therapeutic potential of FICD inhibitors in cellular models of disease.

Main Methods:

• High-throughput screening of small molecules against FICD activity.
• Cell-based assays to assess inhibition of BiP/GRP78 AMPylation and deAMPylation.
• Evaluation of inhibitor efficacy against pathogenic FICD variants and in a β-cell model.

Main Results:

• Two novel small-molecule inhibitors, C22 and C73, were identified.
• C22 and C73 effectively inhibit FICD-mediated BiP/GRP78 AMPylation in cells with minimal impact on deAMPylation.
• Inhibitors demonstrated efficacy against pathogenic FICD variants and improved proinsulin processing in β cells.

Conclusions:

• FICD inhibitors C22 and C73 represent a promising new therapeutic strategy.
• Targeting pathogenic protein AMPylation via FICD inhibition offers a novel approach for treating related human diseases.
• These findings open new avenues for drug development against ER stress-related pathologies.