LRRK2 Facilitates tau Phosphorylation through Strong Interaction with tau and cdk5

Abstract

Leucine-rich repeat kinase 2 (LRRK2) and tau have been identified as risk factors of Parkinson's disease (PD). As LRRK2 is a kinase and tau is hyperphosphorylated in some LRRK2 mutation carriers of PD patients, the obvious hypothesis is that tau could be a substrate of LRRK2. Previous reports that LRRK2 phosphorylates free tau or tubulin-associated tau provide direct support for this proposition. By comparing LRRK2 with cdk5, we show that wild-type LRRK2 and the G2019S mutant phosphorylate free recombinant full-length tau protein with specific activity 480- and 250-fold lower than cdk5, respectively. More strikingly tau binds to wt LRRK2 or the G2019S mutant 140- or 200-fold more strongly than cdk5. The extremely low activity of LRRK2 but strong binding affinity with tau suggests that LRRK2 may facilitate tau phosphorylation as a scaffold protein rather than as a major tau kinase. This hypothesis is further supported by the observation that (i) cdk5 or tau coimmunoprecipitates with endogenous LRRK2 in SH-SY5Y cells, in mouse brain tissue, and in human PBMCs; (ii) knocking down endogenous LRRK2 by its siRNA in SH-SY5Y cells reduces tau phosphorylation at Ser396 and Ser404; (iii) inhibiting LRRK2 kinase activity by its inhibitors has no effect on tau phosphorylation at these two sites; and (iv) overexpressing wt LRRK2, the G2019S mutant, or the D1994A kinase-dead mutant in SH-SY5Y cells has no effect on tau phosphorylation. Our results suggest that LRRK2 facilitates tau phosphorylation indirectly by recruiting tau or cdk5 rather than by directly phosphorylating tau.

Neurite Aggregation and Calcium Dysfunction in iPSC-Derived Sensory Neurons with Parkinson’s Disease-Related LRRK2 G2019S Mutation

“…Tau has been implicated in the pathogenesis of PD in recent genome-wide screens ( Simón-Sánchez et al., 2009 , Edwards et al., 2010 ) and is seen in animal models expressing LRRK2 mutations ( Li et al., 2009b , Lin et al., 2010 , Melrose et al., 2010 ). LRRK2 has been shown to facilitate tau phosphorylation in a kinase-independent manner ( Shanley et al., 2015 ), and our tau data align with previously reported data in LRRK2 G2019S and I2020T iPSC-derived neurons ( Reinhardt et al., 2013 , Ohta et al., 2015 ). Tau hyperphosphorylation has been shown to favor tau detachment from microtubules ( Lindwall and Cole, 1984 ) that can lead to neurofibrillary tangle formation.…”

Aluminum and Neurofibrillary Tangle Co-Localization in Familial Alzheimer’s Disease and Related Neurological Disorders

“…Indeed, tau and ␣-synuclein can interact in cells and their aberrant cross-seeding has been suggested to synergistically enhance protein misfolding and fibrillar inclusions in vivo [7,10]. In addition, PD-specific mutations including those in leucine-rich repeat kinase 2 (LRRK2), has been implicated in the hyperphosphorylation of tau and the subsequent deposition of NFTs [6,40].…”

What Have We Learned from Cerebrospinal Fluid Studies about Biomarkers for Detecting LRRK2 Parkinson’s Disease Patients and Healthy Subjects with Parkinson’s-Associated LRRK2 Mutations?

“…Phosphorylation is thought to increase tau's neurotoxicity [70] but the influence of phosphorylation on ␣-synuclein's toxicity is unclear [71]. Although some studies have suggested that LRRK2 may phosphorylate ␣synuclein [72] and/or tau [73][74][75], the only presently accepted bona fide LRRK2 kinase substrates are LRRK2 protein itself and some Rab GTPases [76,77] such as Rab10, as mentioned above.…”