Substrate and inhibitor specificity of the type II p21-activated kinase, PAK6

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Signaling

Background:

• p21-activated kinases (PAKs) are key downstream effectors of Rho-family small GTPases.
• PAK6, a type II PAK, plays roles in behavior, locomotor function, and androgen receptor signaling.
• Type I and type II PAKs exhibit distinct regulatory and signaling mechanisms.

Purpose of the Study:

• To elucidate the catalytic activity, substrate specificity, and inhibition mechanisms of PAK6.
• To investigate the impact of a melanoma-associated mutation (P52L) on PAK6 activity.
• To determine the structural basis for PAK6 inhibition by ATP-competitive drugs.

Main Methods:

• Peptide substrate specificity assays.
• Analysis of PAK6 activity and substrate phosphorylation in cellular models.
• X-ray crystallography to determine co-crystal structures of PAK6 with inhibitors.

Main Results:

• PAK6 exhibits peptide substrate specificity similar to PAK4 and PAK5.
• Melanoma-associated mutation P52L reduces PAK6 autoinhibition and enhances PACSIN1 phosphorylation.
• Co-crystal structures of PAK6 catalytic domain with PF-3758309 and sunitinib were determined.

Conclusions:

• PAK6 autoinhibition can be modulated by pseudosubstrate mutations.
• Structural insights into PAK6 inhibition by PF-3758309 and sunitinib.
• Findings support the development of targeted PAK6 therapies.