Genetics of Parkinson's Disease: Lysosomal Dysfunction Antibody Sampler Kit

Background

The antibodies in this kit serve to characterize genes implicated in Parkinson’s disease (PD) that lead to lysosomal dysfunction. The cellular function of lysosomes is to degrade and recycle cellular waste, maintaining proper cellular energy metabolism. GBA mutations are the most common genetic risk factor for PD, a neurodegenerative disease characterized by the loss of dopaminergic neurons in the substantia nigra with formation of Lewy bodies in surviving neurons (1,2). In the absence of GBA, which encodes β-glucocerebrosidase (GCase), autophagic lysosome reformation is altered, suggesting that GCase activity is critical to maintaining functional lysosomes. GCase catalyzes the hydrolysis of glucocerebroside into free ceramide and glucose (3). Lysosomal breakdown of glucocerebroside is required for complex lipid cellular metabolism and proper cellular membrane turnover (4).

α-Synuclein (α-Syn) is the main component of pathogenic Lewy bodies and neurites. Research studies have shown that mutations in the α-Synuclein gene are linked to PD (5). Neuronally generated pathogenic species of α-Syn accumulate within neuronal lysosomes and are released via SNARE-dependent lysosomal exocytosis. The released aggregates are non-membrane enveloped and seeding-competent, further contributing to PD pathology (6).

PARK9, also known as ATP13A2, is a member of the P-type ATPase superfamily. It localizes to the lysosomal membrane and is involved in the lysosomal degradation pathway, clearing α-Syn aggregates (7,8).

Cathepsin D (CTSD) is a ubiquitously expressed lysosomal aspartyl protease involved in normal protein degradation. Loss of CTSD leads to lysosomal dysfunction and accumulation of different cellular proteins implicated in neurodegenerative diseases, such as α-Syn (9).

Another gene genetically linked to PD is leucine-rich repeat kinase 2 (LRRK2), also known as PARK8 (10). Research studies have linked at least 20 mutations in LRRK2 to PD, with the G2019S mutation being the most prevalent (11). LRRK2 mutations alter lysosome morphology, distribution, pH, and degradative capacity in many distinct cell types, including fibroblasts, striatal neurons, primary neurons, and primary astrocytes (12).

Mutations in the vacuolar protein sorting-associated protein 35 (VPS35) gene, encoding a core component of the retromer complex, have recently emerged as a new cause of late-onset, autosomal dominant familial PD. A single missense mutation, Asp620Asn (D620N), has so far been unambiguously identified to cause PD (13). The VPS35 D620N mutation alters the expression of ~220 lysosomal proteins and stimulates recruitment of LRRK2 and phosphorylation of Rab proteins at the lysosome (14).