Structure of the Human Protein Kinase ZAK in Complex with Vemurafenib

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Mixed lineage kinase ZAK is a critical regulator of the MAPK pathway, influencing cell survival and inflammatory responses.
• ZAK is a target for approved kinase inhibitors, with potential therapeutic roles in doxorubicin-induced cardiomyopathy and cancer.
• Off-target inhibition of ZAK by anticancer drugs can lead to adverse effects like cutaneous squamous cell carcinoma.

Purpose of the Study:

• To elucidate the structural basis for ZAK inhibition and substrate specificity.
• To identify specific ZAK inhibitors and anticancer drugs lacking off-target ZAK activity for therapeutic benefit.
• To provide insights for rational inhibitor design targeting ZAK.

Main Methods:

• Determined the crystal structure of ZAK in complex with the B-RAF inhibitor vemurafenib.
• Analyzed ZAK-specific structural features, including the P loop conformation.
• Utilized positional scanning peptide library analysis to define ZAK substrate specificity.
• Screened a library of clinical kinase inhibitors for ZAK inhibitory activity.

Main Results:

• The first crystal structure of ZAK in complex with vemurafenib revealed ZAK-specific features, including a distorted P loop.
• Positional scanning peptide library analysis identified unique substrate preferences for histidine residues at positions -1 and +2.
• Screening identified several clinical kinase inhibitors that potently inhibit ZAK, indicating common mistargeting.

Conclusions:

• The ZAK-vemurafenib cocrystal structure provides a foundation for rational inhibitor design.
• ZAK exhibits unique substrate specificity, offering opportunities for targeted therapeutic strategies.
• Many current anticancer drugs unintentionally inhibit ZAK, highlighting the need for developing specific inhibitors or ZAK-sparing agents.