Disruption of the LRRK2‐FADD Interface Using Constrained Peptides

Mutations in the gene encoding leucine‐rich repeat kinase 2 (LRRK2) are the most common cause of familial Parkinson's disease (PD). The reduced penetrance of mutations in the LRRK2 gene has also led to variants appearing in seemingly sporadic forms of the disease. Kinase inhibition effectively blocks neuronal death and small‐molecule Class I inhibitors are proceeding through clinical trials in multiple PD cohorts. The toxic interaction between mutant LRRK2 and FADD lies downstream of its kinase activity and is required to induce neuronal death. The present study aimed to determine whether the FADD‐LRRK2 interface could be disrupted and what effects this may have on neuroprotection. A series of constrained peptides were designed to mimic the alpha‐helical protein interaction interface between the LRRK2 armadillo region and the death domain of FADD. These peptide‐based protein–protein interaction inhibitors significantly reduced this interaction and blocked apoptotic death of primary neurons expressing G2019S‐LRRK2. This work has identified novel constrained peptides that disrupt the LRRK2‐FADD interface and downregulate mutant LRRK2‐induced neuronal death in an allosteric manner, thereby providing a potential alternative therapeutic approach for PD.