Leucine-Rich Repeat Kinase 2 (LRRK2) is a large, multidomain protein with dual kinase and GTPase function that is commonly mutated in both familial and idiopathic Parkinson’s Disease (PD). While dimerization of LRRK2 is commonly detected in PD models, it remains unclear whether inhibition of dimerization can regulate catalytic activity and pathogenesis. Here, we show constrained peptides that are cell-penetrant, bind LRRK2, and inhibit LRRK2 activation by downregulating dimerization. We further show that inhibited dimerization decreases kinase activity and inhibits ROS production and PD-linked apoptosis in primary cortical neurons. While many ATP-competitive LRRK2 inhibitors induce toxicity and mislocalization of the protein in cells, these constrained peptides were found to not affect LRRK2 localization. The ability of these peptides to inhibit pathogenic LRRK2 kinase activity suggests that disruption of dimerization may serve as a new allosteric strategy to downregulate PD-related signaling pathways.

Malaria remains a worldwide health concern with an estimated quarter of a billion people infected and nearly half a million deaths annually. Malaria is caused by a parasite infection from Plasmodium strains which are transmitted from mosquitoes into the human host. Although several small molecule inhibitors have been found to target the early stages of transmission and prevent parasite proliferation, multiple drug resistant parasite strains have emerged and drug resistance remains a major hurdle. As an alternative to small molecule inhibition, several peptide-based therapeutics have been explored for their potential as antimalarial compounds. Chemically constrained peptides or peptidomimetics were developed to target large binding interfaces of parasite-based proteins that have historically been difficult to selectively inhibit using small molecules. Here, we review ongoing research aimed at developing constrained peptides targeting protein-protein interactions pertinent to malaria pathogenesis. These targets include Falcipain-2, the J domain of CDPK1, myosin A tail domain interacting protein, the PKA signaling pathway, and an unclear signaling pathway involving angiotensin-derived peptides. Diverse synthetic methods were also used for each target. Merging parasite biology with synthetic strategies may provide new opportunities to develop alternative methods for uncovering novel antimalarials and may offer an alternate source for targeting drug-resistant parasite strains.

Wiskott−Aldrich Syndrome Protein Family (WASF) members regulate actin cytoskeletal dynamics, and WASF3 is directly associated with breast cancer metastasis and invasion. WASF3 forms a heteropentameric complex with CYFIP, NCKAP, ABI, and BRK1, called the WASF Regulatory Complex (WRC), which cooperatively regulates actin nucleation by WASF3. Since aberrant deployment of the WRC is observed in cancer metastasis and invasion, its disruption provides a novel avenue for targeting motility in breast cancer cells. Here, we report the development of a second generation WASF3 mimetic peptide, WAHMIS-2, which was designed using a combination of structure-guided design, homology modeling, and in silico optimization to disrupt binding of WASF3 to the WRC. WAHMIS-2 was found to permeate cells and inhibit cell motility, invasion, and MMP9 expression with greater potency than its predecessor, WAHM1. Targeted disruption of WASF3 from the WRC may serve as a useful strategy for suppression of breast cancer metastasis.

Missense mutations along the leucine-rich repeat kinase 2 (LRRK2) protein are a major contributor to Parkinson’s Disease (PD), the second most commonly occurring neurodegenerative disorder worldwide. We recently reported the development of allosteric constrained peptide inhibitors that target and downregulate LRRK2 activity through disruption of LRRK2 dimerization. In this study, we designed doubly constrained peptides with the objective of inhibiting C-terminal of Roc (COR)–COR mediated dimerization at the LRRK2 dimer interface. We show that the doubly constrained peptides are cell-permeant, bind wild-type and pathogenic LRRK2, inhibit LRRK2 dimerization and kinase activity, and inhibit LRRK2-mediated neuronal apoptosis, and in contrast to ATP-competitive LRRK2 kinase inhibitors, they do not induce the mislocalization of LRRK2 to skein-like structures in cells. This work highlights the significance of COR-mediated dimerization in LRRK2 activity while also highlighting the use of doubly constrained peptides to stabilize discrete secondary structural folds within a peptide sequence.

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