| Mutations in leucine-rich repeat kinase 2 (LRRK2 ) are the most common known cause of inherited Parkinson's disease (PD), and LRRK2 is a risk factor for idiopathic PD. How LRRK2 function is regulated is not well understood. Recently, the highly-conserved 14-3-3 proteins, which play a key role in many cellular functions including cell death, have been shown to interact with LRRK2. In this study, we investigated whether 14-3-3s can regulate mutant LRRK2-induced neurite shortening and kinase activity. In the presence of 14-3-3&thgr; overexpression, neurite length of primary neurons from BAC transgenic G2019S-LRRK2 mice returned back to wildtype levels. Similarly, 14-3-3&thgr; overexpression reversed neurite shortening in neuronal cultures from BAC transgenic R1441G-LRRK2 mice. Conversely, inhibition of 14-3-3s by the pan-14-3-3 inhibitor difopein or dominant negative 14-3-3&thgr; further reduced neurite length in G2019S-LRRK2 cultures. Since G2019S-LRRK2 toxicity is likely mediated through increased kinase activity, we examined 14-3-3&thgr;'s effects on LRRK2 kinase activity. 14-3-3&thgr; overexpression reduced the kinase activity of G2019S-LRRK2, while difopein promoted the kinase activity of G2019S-LRRK2. The ability of 14-3-3s to reduce LRRK2 kinase activity required direct binding of 14-3-3&thgr; with LRRK2. The potentiation of neurite shortening by difopein in G2019S-LRRK2 neurons was reversed by LRRK2 kinase inhibitors. Taken together, we conclude that 14-3-3&thgr; can regulate LRRK2 and reduce the toxicity of mutant LRRK2 through a reduction of kinase activity. |
