Differential protein-protein interactions of LRRK1 and LRRK2 indicate roles in distinct cellular signaling pathways

Genetic studies show that LRRK2, and not its closest
paralogue LRRK1, is linked to Parkinson’s disease. To gain
insight into the molecular and cellular basis of this discrepancy,
we searched for LRRK1- and LRRK2-specic cellular
processes by identifying their distinct interacting proteins. A
protein microarray-based interaction screen was performed
with recombinant 3xFlag-LRRK1 and 3xFlag-LRRK2 and, in
parallel, co-immunoprecipitation followed by mass spectrometry
was performed from SH-SY5Y neuroblastoma cell lines
stably expressing 3xFlag-LRRK1 or 3xFlag-LRRK2. We identi
ed a set of LRRK1- and LRRK2-specic as well as common
interactors. One of our most prominent ndings was that both
screens pointed to epidermal growth factor receptor (EGF-R)
as a LRRK1-specic interactor, while 14-3-3 proteins were
LRRK2-specic. This is consistent with phosphosite mapping
of LRRK1, revealing phosphosites outside of 14-3-3 consensus
binding motifs. To assess the functional relevance of
these interactions, SH-SY5Y-LRRK1 and -LRRK2 cell lines
were treated with LRRK2 kinase inhibitors that disrupt 14-3-3
binding, or with EGF, an EGF-R agonist. Redistribution of
LRRK2, not LRRK1, from diffuse cytoplasmic to lamentous
aggregates was observed after inhibitor treatment. Similarly,
EGF induced translocation of LRRK1, but not of LRRK2, to
endosomes. Our study conrms that LRRK1 and LRRK2 can
carry out distinct functions by interacting with different cellular
proteins.