Understanding the role of the LRRK2 tail in the crosstalk between kinase and the N-terminal domains.

Abstract

LRRK2 is a multi-domain protein encompassing biology's two most critical molecular switches; a kinase and a GTPase. Mutations in LRRK2 are one of the key players in the pathogenesis of Parkinson's disease (PD). The availability of multiple structures (full-length and truncated) has opened doors to exploring the physiological role of LRRK2. A helix extending from the WD40 domain and stably docking onto the kinase domain is a common feature in all available structures. This C-terminal (Ct) helix is a hub of phosphorylation and organelle-localization motifs and can serve as a multi-functional protein: protein interaction module. To examine its intra-domain interactions, we have recombinantly expressed a stable Ct motif (residues 2480-2527) and are using peptide arrays to identify specific binding sites. We have identified a potential interaction site between the Ct helix and a loop in the CORB region with a combination of Gaussian MD simulations and peptide arrays. This Ct-Motif contains multiple phosphorylation sites including two auto-phosphorylation sites (Thr2083 and Thr2524), a 14-3-3 binding site (Thr2524) and a putative PKA phosphorylation site. These two sites together form a part of a dynamic “CAP” that regulates the N-lobe of the kinase domain. We also explore how the cellular localization of LRRK2RCKW and its docking onto microtubules is altered by mutations in the Ct helix, if at all. We hypothesize that in inactive, full-length LRRK2, the Ct-helix will mediate interactions with the N-terminal armadillo, ankyrin, and LRR domains (NTDs) and that binding of Rab substrates, PD mutations, or kinase inhibitors will unleash the NTDs.