The multifaceted functions of ß-arrestins and their therapeutic potential in neurodegenerative diseases.

Arrestins are multifunctional proteins that regulate G-protein-coupled receptor (GPCR) desensitization, signaling, and internalization. The arrestin family consists of four subtypes: visual arrestin1, ß-arrestin1, ß-arrestin2, and visual arrestin-4. Recent studies have revealed the multifunctional roles of ß-arrestins beyond GPCR signaling, including scaffolding and adapter functions, and physically interacting with non-GPCR receptors. Increasing evidence suggests that ß-arrestins are involved in the pathogenesis of a variety of neurodegenerative diseases, including Alzheimer's disease (AD), frontotemporal dementia (FTD), and Parkinson's disease (PD). ß-arrestins physically interact with γ-secretase, leading to increased production and accumulation of amyloid-beta in AD. Furthermore, ß-arrestin oligomers inhibit the autophagy cargo receptor p62/SQSTM1, resulting in tau accumulation and aggregation in FTD. In PD, ß-arrestins are upregulated in postmortem brain tissue and an MPTP model, and the ß2AR regulates SNCA gene expression. In this review, we aim to provide an overview of ß-arrestin1 and ß-arrestin2, and describe their physiological functions and roles in neurodegenerative diseases. The multifaceted roles of ß-arrestins and their involvement in neurodegenerative diseases suggest that they may serve as promising therapeutic targets.

Pathological characterization of a novel mouse model expressing the PD-linked CHCHD2-T61I mutation.

Coiled-coil-helix-coiled-coil-helix domain containing 2 (CHCHD2) is a mitochondrial protein that plays important roles in cristae structure, oxidative phosphorylation and apoptosis. Multiple mutations in CHCHD2 have been associated with Lewy body disorders (LBDs), such as Parkinson's disease (PD) and dementia with Lewy bodies, with the CHCHD2-T61I mutation being the most widely studied. However, at present, only CHCHD2 knockout or CHCHD2/CHCHD10 double knockout mouse models have been investigated. They do not recapitulate the pathology seen in patients with CHCHD2 mutations. We generated the first transgenic mouse model expressing the human PD-linked CHCHD2-T61I mutation driven by the mPrP promoter. We show that CHCHD2-T61I Tg mice exhibit perinuclear mitochondrial aggregates, neuroinflammation, and have impaired long-term synaptic plasticity associated with synaptic dysfunction. Dopaminergic neurodegeneration, a hallmark of PD, is also observed along with α-synuclein pathology. Significant motor dysfunction is seen with no changes in learning and memory at 1 year of age. A minor proportion of the CHCHD2-T61I Tg mice (~10%) show a severe motor phenotype consistent with human Pisa Syndrome, an atypical PD phenotype. Unbiased proteomics analysis reveals surprising increases in many insoluble proteins predominantly originating from mitochondria and perturbing multiple canonical biological pathways as assessed by ingenuity pathway analysis, including neurodegenerative disease-associated proteins such as tau, cofilin, SOD1 and DJ-1. Overall, CHCHD2-T61I Tg mice exhibit pathological and motor changes associated with LBDs, indicating that this model successfully captures phenotypes seen in human LBD patients with CHCHD2 mutations and demonstrates changes in neurodegenerative disease-associated proteins, which delineates relevant pathological pathways for further investigation.