Selectivity profiles and substrate recognition of Rab-phosphorylating kinases

Area of Science:

• Cellular Biology
• Biochemistry
• Neuroscience

Background:

• The Rab GTPase switch-2 region is crucial for cellular processes and is a site for post-translational modifications.
• Phosphorylation of Rab GTPases is implicated in Parkinson's disease pathogenesis and bacterial infections.
• Understanding kinase-Rab interactions is vital for deciphering cellular signaling pathways.

Purpose of the Study:

• To profile kinases for their ability to phosphorylate Rab GTPases.
• To identify novel kinase-Rab interactions.
• To investigate the determinants of Rab GTPase phosphorylation and engineer variants for functional studies.

Main Methods:

• Kinase screening assays were performed using LRRK1, LRRK2, DYRK1A, MST1, and TBK1 against various Rab GTPases.
• Systematic mutational analysis was employed to identify key residues and regions influencing Rab phosphorylation.
• Cellular models were utilized to validate the functional impact of engineered Rab variants.

Main Results:

• Several novel kinase-Rab pairs were identified, including LRRK1:Rab43 and TBK1:Rab29.
• The Rab nucleotide-binding state and primary sequence significantly influence kinase substrate specificity.
• A LRRK2 recognition patch on the Rab α3 helix was identified, with specific mutations increasing LRRK2 phosphorylation by 18-fold.
• Engineered Rab variants demonstrated altered phosphorylation properties in vitro and in cellular models.

Conclusions:

• Rab GTPases are suboptimal substrates for LRRK2, suggesting regulatory mechanisms.
• The identified Rab variants serve as valuable tools for investigating the physiological roles of Rab phosphorylation.
• This research provides new insights into the regulation of Rab GTPases and their potential links to neurodegenerative diseases.