Here we review current knowledge about the ATP13A2 gene, clinical characteristics of patients with PD-associated ATP13A2 mutations, and models of how the ATP13A2 protein may help prevent neurodegeneration by inhibiting α-synuclein aggregation and supporting normal lysosomal and mitochondrial function.
Mutations in the ATP13A2 gene (PARK9, CLN12, OMIM 610513) were initially associated with a form of Parkinson's Disease (PD) known as Kufor Rakeb Syndrome (KRS).
At least some P5B isoforms are of vital importance for the nervous system, since ATP13A2 and ATP13A4 are linked to respectively Parkinson disease and autism spectrum disorders.
Thus, the N-terminal binding of PA and PI(3,5)P2 emerges as a key to unlock the activity of ATP13A2, which may offer a therapeutic strategy to activate ATP13A2 and thereby reduce α-synuclein toxicity or mitochondrial stress in PD or related disorders.
These discoveries provide a new understanding of the role that ATP13A2 plays in the development of PD and identify a therapeutic target that may ameliorate α-synuclein accumulation and lysosomal and mitochondrial dysfunction in Parkinson's disease.
Some of them are implicated in the development of either autosomal dominant (alpha-synuclein and LRRK2 (leucine-rich repeat kinase 2/dardarin) or early-onset recessive (parkin, DJ-1, PINK1 (PTEN-induced kinase-1) and ATP13A2) PD forms.
Collectively, our data demonstrate a distinct lack of ATP13A2-mediated protection against α-synuclein-induced neurotoxicity in the rat nigrostriatal dopaminergic pathway, and limited neuroprotective capacity overall, and raise doubts about the potential of ATP13A2 as a therapeutic target for PD.
This constitutes a heretofore unrecognized process associated with loss of ATP13A2 function that could have wide-ranging implications for it as a therapeutic target for PD and other related conditions.
Conversely, mutations in lysosomal-related genes, such as glucocerebrosidase (GBA) and lysosomal type 5 P-type ATPase (ATP13A2), have been linked to PD.
These variants included loss of function and missense changes in 18 genes that were never previously linked to PD (NOTCH4, BCOR, ITM2B, HRH4, CELSR1, SNAP91, FAM174A, BSN, SPG7, MAGI2, HEPHL1, EPRS, PUM1, CLSTN1, PLCB3, CLSTN3, DNAJB9 and NEFH) and 2 genes that were previously associated with PD (EIF4G1 and ATP13A2).
Our data suggested that TXNIP blocked autophagic flux and induced α-synuclein accumulation through inhibition of ATP13A2, indicating TXNIP was a disease-causing protein in PD.
Using voxel-based morphometry in 30 asymptomatic mutation carriers (MC) with mutations in four different genes for PD and 100 healthy controls, we identified an increase in gray matter volume (GMV) in the striatum in asymptomatic Parkin, PINK1, ATP13A2 and, to a much lesser extent, in LRRK2 MC.
Our data indicate that ATP13A2 is the first PD-associated gene involved in exosome biogenesis and indicates a potential neuroprotective role of exosomes in PD.