Structural basis and biological consequences for JNK2/3 isoform selective aminopyrazoles

Area of Science:

• Neuroscience
• Molecular Biology
• Pharmacology

Background:

• Three JNK (c-Jun N-terminal kinase) isoforms (JNK1, JNK2, JNK3) exist with distinct biological roles.
• The therapeutic and safety benefits of selectively inhibiting these JNK isoforms remain unclear.

Purpose of the Study:

• To develop selective JNK2/3 inhibitors with >30-fold selectivity over JNK1.
• To investigate the protective effects of JNK2/3 selective inhibitors on human dopaminergic neurons against neurotoxin-induced mitochondrial dysfunction.

Main Methods:

• Utilized site-directed mutagenesis and X-ray crystallography to identify key residues for JNK selectivity.
• Assessed reactive oxygen species (ROS) generation and mitochondrial membrane potential (MMP) in response to 6-hydroxydopamine.
• Employed JNK2/3 selective inhibitors in cellular models of neurotoxicity.

Main Results:

• Identified Leucine 144 (L144) in JNK3 as crucial for inhibitor selectivity.
• Demonstrated that JNK2/3 selective inhibitors protected dopaminergic neurons from 6-hydroxydopamine-induced ROS generation.
• Showed protection against mitochondrial membrane potential (MMP) depolarization in treated neurons.

Conclusions:

• Confirmed the feasibility of developing JNK2/3 selective inhibitors, with selectivity attributed to hydrophobic pocket I residues.
• Indicated that selective inhibition of JNK2/3 contributes to mitochondrial protection and prevention of neuronal cell death.
• Suggests a potential therapeutic strategy targeting JNK2/3 for neurodegenerative diseases.