Interferon-γ signaling synergizes with LRRK2 in human neurons and microglia

Increasing evidence suggests a role for interferons (IFNs) in neurodegeneration. Parkinson’s disease (PD) associated kinase LRRK2 has been implicated in IFN type II (IFN) response in infections and nigral neuronal loss. However, whether and how LRRK2 synergizes with IFN-γ still remains unclear. Here, we employed dopaminergic (DA) neurons and microglia differentiated from patient induced pluripotent stem cells to unravel the role of IFN-γ in LRRK2-PD. We show that IFN-γ induces LRRK2 expression in both DA neurons and microglial cells. LRRK2-G2019S, the most common PD-associated mutation, sensitizes DA neurons to IFN-γ by decreasing AKT phosphorylation. IFN-γ suppresses NFAT activity in both neurons and microglia and synergistically enhances LRRK2-induced defects of NFAT activation. Furthermore, LRRK2-G2019S negatively regulates NFAT via calcium and microtubule dynamics. Importantly, we uncover functional consequences of the reduction of NFAT activity in both cell types, namely defects of neurite elongation and alteration of microglial activation profile and motility. We propose that synergistic IFN-γ/LRRK2 activation serves as a direct link between inflammation and neurodegeneration in PD.