A novel ATP13A2 variant causing complicated hereditary spastic paraplegia.

BACKGROUND: ATP13A2 is a monogenic causative gene of Parkinson's disease, whose biallelic mutations can result in Kufor-Rakeb syndrome. Biallelic mutations in ATP13A2 have also been reported in pure or complicated hereditary spastic paraplegia (HSP). Here, we report clinical, neuroimaging, and genetic findings from a patient with a novel homozygous mutation in ATP13A2 presenting with HSP plus parkinsonism. METHODS: Whole genome sequencing was performed on the patient, a 46-year-old Chinese woman from a consanguineous family, to identify the genetic cause. Furthermore, functional studies of the identified ATP13A2 mutation were conducted. RESULTS: The patient initially presented with abnormal gait because of lower-limb spasticity and recurrent seizures. Parkinsonism (presenting as bradykinesia and rigidity) and peripheral neuropathy in lower limbs further evolved and resulted in her eventual use of a wheelchair. Symmetrically decreased dopamine transporter density was detected within the bilateral putamen and caudate nucleus in dopamine transporter-positron emission tomography. Genetic analysis revealed a novel homozygous missense mutation in ATP13A2 (c.2780 T > C, p.Leu927Pro), which was heterozygous in the patient's parents and son. Functional studies suggested that this mutation results in the reduced expression and altered subcellular localization of ATP13A2. CONCLUSIONS: Our report broadens the genetic and phenotypic spectrum of ATP13A2-related HSP. Further research is needed to fully elucidate the mechanism linking ATP13A2 variants to HSP.

Manganese-Induced Parkinsonism: Evidence from Epidemiological and Experimental Studies.

Manganese (Mn) exposure has evolved from acute, high-level exposure causing manganism to low, chronic lifetime exposure. In this latter scenario, the target areas extend beyond the globus pallidus (as seen with manganism) to the entire basal ganglia, including the substantia nigra pars compacta. This change of exposure paradigm has prompted numerous epidemiological investigations of the occurrence of Parkinson's disease (PD), or parkinsonism, due to the long-term impact of Mn. In parallel, experimental research has focused on the underlying pathogenic mechanisms of Mn and its interactions with genetic susceptibility. In this review, we provide evidence from both types of studies, with the aim to link the epidemiological data with the potential mechanistic interpretation.

ATP13A2 activates the pentose phosphate pathway to promote colorectal cancer growth though TFEB-PGD axis.

BACKGROUND: The pentose phosphate pathway (PPP) is an important mechanism by which tumour cells resist stressful environments and maintain malignant proliferation. However, the mechanism by which the PPP regulates these processes in colorectal cancer (CRC) remains elusive. METHODS: Closely related PPP genes were obtained from the TCGA and GEO databases. The effect of ATP13A2 on CRC cell proliferation was evaluated by performing in vitro assays. The connection between the PPP and ATP13A2 was explored by assessing proliferation and antioxidative stress. The molecular mechanism by which ATP13A2 regulates the PPP was investigated using chromatin immunoprecipitation and dual luciferase experiments. The clinical therapeutic potential of ATP13A2 was explored using patient-derived xenograft (PDX), patient-derived organoid (PDO) and AOM/DSS models. FINDINGS: We identified ATP13A2 as a novel PPP-related gene. ATP13A2 deficiency inhibited CRC growth and PPP activity, as manifested by a decrease in the levels of PPP products and an increase in reactive oxygen species levels, whereas ATP13A2 overexpression induced the opposite effect. Mechanistically, ATP13A2 regulated the PPP mainly by affecting phosphogluconate dehydrogenase (PGD) mRNA expression. Subsequent studies showed that ATP13A2 overexpression promoted TFEB nuclear localization by inhibiting the phosphorylation of TFEB, thereby enhancing the transcription of PGD and ultimately affecting the activity of the PPP. Finally, ATP13A2 knockdown inhibited CRC growth in PDO and PDX models. ATP13A2- /- mice had a lower CRC growth capacity than ATP13A2+/+ in the AOM/DSS model.Our findings revealed that ATP13A2 overexpression-driven dephosphorylation of TFEB promotes PPP activation by increasing PGD transcription, suggesting that ATP13A2 may serve as a potential target for CRC therapy.

ATP13A2 Gene Silencing in Drosophila Affects Autophagic Degradation of A53T Mutant α-Synuclein.

Mutations in ATP13A2 (PARK9), an autophagy-related protein, cause Kufor-Rakeb syndrome, an autosomal recessive, juvenile-onset form of parkinsonism. α-Synuclein (α-syn) is a presynaptic neuronal protein that forms toxic aggregates in Parkinson's disease (PD). We studied α-syn aggregation and autophagic flux in ATP13A2-knockdown Drosophila expressing either wild-type (WT) or mutant α-syn. Dopaminergic (DA) neuron loss was studied by confocal microscopy. Sleep and circadian activity were evaluated in young and old flies using a Drosophila activity monitor. Thirty-day-old ATP13A2-RNAi A53T-α-syn flies had increased Triton-insoluble α-syn levels, compared to control A53T-α-syn flies without ATP13A2-RNAi. Whole-brain staining revealed significantly fewer dopaminergic (DA) neurons in the PPL2 cluster of 30-day-old ATP13A2-RNAi flies expressing WT-, A30P-, and A53T-α-syn than in that of controls. In ATP13A2-RNAi A53T-α-syn flies, autophagic flux was decreased, as indicated by increased accumulation of Ref(2)P, the Drosophila p62 homologue. ATP13A2 silencing decreased total locomotor activity in young, and enhanced sleep features, similar to PD (decreasing bout length), in old flies expressing A53T-α-syn. ATP13A2 silencing also altered the circadian locomotor activity of A30P- and A53T-α-syn flies. Thus, ATP13A2 may play a role in the autophagic degradation of A53T-α-syn.

ATP13A2 is a Prognostic Biomarker and Correlates with Immune Infiltrates in Hepatocellular Carcinoma.

PURPOSE: To explore the expression and role of ATPase cation transporting 13A2 (ATP13A2) on hepatocellular carcinoma (HCC) progression and prognosis. METHODS: The level of ATP13A2 in 63 HCC tissues was evaluated by quantitative real-time polymerase chain reaction, Western blot, and immunohistochemistry. Then, the prognostic value of ATP13A2 for HCC was explored. GO and KEGG pathway enrichments were performed to predict ATP13A2-mediated biological functions. Besides, the correlations between ATP13A2 and key regulators involved in cell cycle and metastasis, the status of different tumor-infiltrating immune cells was investigated. RESULTS: ATP13A2 was frequently upregulated in 63 HCC tissues relatively to matched non-tumor tissues. The level of ATP13A2 significantly correlated with tumor stage and tumor grade. HCC patients with higher levels of ATP13A2 had a worse prognosis. Moreover, multivariate survival analysis supported ATP13A2 to be an independent prognostic factor for HCC. GO and KEGG analysis indicated a potential role of ATP13A2 on regulating cell cycle, metastasis, and immune infiltrates. Especially, the level of ATP13A2 was positively correlated with CCNB1, CCND3, CDC25B, CDK4, Vimentin, MMP9, MMP14, and LMNB2. A positive correlation was noticed between ATP13A2 and infiltration levels of B cells, CD8+ T cells, CD4+ T cells, macrophages, neutrophils, dendritic cells, monocytes, M2 macrophages, and exhausted T cells in HCC. CONCLUSION: Upregulation of ATP13A2 is a common feature as well as an independent prognostic biomarker for HCC. ATP13A2 are associated with key regulators involved in cell cycle, metastasis, and immune infiltrates in HCC, and may act as a potential immunotherapy target for HCC.

Salivary ATP13A2 is a potential marker of therapy-induced motor complications and is expressed by inclusions in submandibulary glands in Parkinson ´s disease.

Background: ATP13A2 holds promise as biomarker for Parkinsons disease (PD). No study has examined how salivary ATP13A2 is related to motor features in idiopathic PD. Methods: Salivary ATP13A2 concentration was evaluated with ELISA, and statistical correlations of ATP13A2 level with PD parameters were examined. The dose intensity of the dopaminergic medication regimen was expressed as levodopa equivalent daily dose (LEDD). ATP13A2 expression on histological sections of submandibular glands was evaluated using immunohistochemistry. Results: Salivary ATP13A2 was undetectable in many subjects (28 % of patients, 43.7 % of controls). However, all the patients with motor complications (n = 28) showed quantifiable levels of ATP13A2, that positively correlated with MDS-UPDRS (total, parts III and IV), and LEDD (p < 0.05). Dyskinetic patients showed the highest LEDD values (p < 0.05). The histological study revealed: a) ATP13A2 staining was very intense in duct cells and vascular endothelium, and b) two patterns of ATP13A2-positive deposits are observed: rounded inclusions of 10-20 µm in diameter located in the interlobular tissue of the patients, and amorphous aggregates inside duct lumen in controls and patients. Conclusions: The sensitivity of the ELISA assay was a major limitation for quantifying ATP13A2. However, salivary ATP13A2 was detected in all patients with motor complications, where a direct relationship among ATP13A2 concentration, levodopa equivalent daily dose, and MDS-UPDRS was found. Therefore, salivary ATP13A2 might be a reliable index of therapy-induced motor complications. ATP13A2 was expressed by rounded inclusions in the submandibulary gland of patients. This is the first description of ATP13A2-positive inclusions outside the nervous system.

The Roles of ATP13A2 Gene Mutations Leading to Abnormal Aggregation of α-Synuclein in Parkinson's Disease.

Parkinson's disease (PD) is the second most common neurodegenerative disease. PARK9 (also known as ATP13A2) is recognized as one of the key genes that cause PD, and a mutation in this gene was first discovered in a rare case of PD in an adolescent. Lewy bodies (LBs) formed by abnormal aggregation of α-synuclein, which is encoded by the SNCA gene, are one of the pathological diagnostic criteria for PD. LBs are also recognized as one of the most important features of PD pathogenesis. In this article, we first summarize the types of mutations in the ATP13A2 gene and their effects on ATP13A2 mRNA and protein structure; then, we discuss lysosomal autophagy inhibition and the molecular mechanism of abnormal α-synuclein accumulation caused by decreased levels and dysfunction of the ATP13A2 protein in lysosomes. Finally, this article provides a new direction for future research on the pathogenesis and therapeutic targets for ATP13A2 gene-related PD from the perspective of ATP13A2 gene mutations and abnormal aggregation of α-synuclein.

ATP13A2 Declines Zinc-Induced Accumulation of α-Synuclein in a Parkinson's Disease Model.

Parkinson's disease (PD) is characterized by the presence of Lewy bodies caused by α-synuclein. The imbalance of zinc homeostasis is a major cause of PD, promoting α-synuclein accumulation. ATP13A2, a transporter found in acidic vesicles, plays an important role in Zn2+ homeostasis and is highly expressed in Lewy bodies in PD-surviving neurons. ATP13A2 is involved in the transport of zinc ions in lysosomes and exosomes and inhibits the aggregation of α-synuclein. However, the potential mechanism underlying the regulation of zinc homeostasis and α-synuclein accumulation by ATP13A2 remains unexplored. We used α-synuclein-GFP transgenic mice and HEK293 α-synuclein-DsRed cell line as models. The spatial exploration behavior of mice was significantly reduced, and phosphorylation levels of α-synuclein increased upon high Zn2+ treatment. High Zn2+ also inhibited the autophagy pathway by reducing LAMP2a levels and changing the expression of LC3 and P62, by reducing mitochondrial membrane potential and increasing the expression of cytochrom C, and by activating the ERK/P38 apoptosis signaling pathway, ultimately leading to increased caspase 3 levels. These protein changes were reversed after ATP13A2 overexpression, whereas ATP13A2 knockout exacerbated α-synuclein phosphorylation levels. These results suggest that ATP13A2 may have a protective effect on Zn2+-induced abnormal aggregation of α-synuclein, lysosomal dysfunction, and apoptosis.

ATP13A2 protects dopaminergic neurons in Parkinson's disease: from biology to pathology.

As a late endosomal/lysosomal transport protein of the P5-type, ATP13A2 is capable of removing the abnormal accumulation of α-synuclein, which maintains the homeostasis of metal ions and polyamines in the central nervous system. Furthermore, ATP13A2 regulates the normal function of several organelles such as lysosomes, endoplasmic reticulum (ER) and mitochondria, and maintains the normal physiological activity of neural cells. Especially, ATP13A2 protects dopaminergic (DA) neurons against environmental or genetically induced Parkinson's disease (PD). As we all know, PD is a neurodegenerative disease characterized by the loss of DA neurons in the substantia nigra pars compacta. An increasing number of studies have reported that the loss-of-function of ATP13A2 affects normal physiological processes of various organelles, leading to abnormalities and the death of DA neurons. Previous studies in our laboratory have also shown that ATP13A2 deletion intensifies the neuroinflammatory response induced by astrocytes, thus inducing DA neuronal injury. In addition to elucidating the normal structure and function of ATP13A2, this review summarized the pathological mechanisms of ATP13A2 mutations leading to PD in existing literature studies, deepening the understanding of ATP13A2 in the pathological process of PD and other related neurodegenerative diseases. This review provides inspiration for investigators to explore the essential regulatory role of ATP13A2 in PD in the future.

YPK9 and WHI2 Negatively Interact during Oxidative Stress.

Yeast PARK9 (YPK9) shares homology with human ATP13A2, which encodes a polyamine transporter implicated in juvenile forms of Parkinson's disease. We used YPK9 to gain insight into how ATP13A2 affects cell growth and sensitivity to oxidative stress. Surprisingly, the YPK9 deletion strain from the Saccharomyces cerevisiae deletion collection (YKO) in wildtype BY4741 (mating type a) grew faster and was more resistant to hydrogen peroxide than a commercial, putative parental BY4741 wildtype strain (BY4741COM). In contrast, deleting YPK9 from BY4741COM rendered it very sensitive to hydrogen peroxide, suggesting its background is different from that of the deletion collection. Whole-genome sequencing revealed that BY4741COM and BY4741COMypk9∆ contain a novel premature stop codon near the 3' end of WHI2 (WHI2G1324T), whereas the collection's YPK9 deletion strain contains WHI2, which encodes a 486 amino acid protein, Whi2p. Replacing full-length WHI2 with the sequence coding for the predicted truncation (Whi2pE442*) rendered strains more sensitive to hydrogen peroxide, whereas the converse replacement rendered them more resistant. The sequences of WHI2 in 20 randomly chosen strains from the collection encode the full-length protein, indicating that the putative parental BY4741 WHI2G1324T strain's genetic background differs from that of the deletion collection. Examination of WHI2 sequences in several commonly used wildtype S. cerevisiae strains and isolates revealed other Whi2p truncations that might yield altered phenotypes. Together, these results demonstrate a novel premature stop codon in WHI2 that renders yeast sensitive to hydrogen peroxide; they also reveal a negative genetic interaction between WHI2 and YPK9 in the presence of hydrogen peroxide in the BY4741 background.

Targeting autophagy using small-molecule compounds to improve potential therapy of Parkinson's disease.

Parkinson's disease (PD), known as one of the most universal neurodegenerative diseases, is a serious threat to the health of the elderly. The current treatment has been demonstrated to relieve symptoms, and the discovery of new small-molecule compounds has been regarded as a promising strategy. Of note, the homeostasis of the autolysosome pathway (ALP) is closely associated with PD, and impaired autophagy may cause the death of neurons and thereby accelerating the progress of PD. Thus, pharmacological targeting autophagy with small-molecule compounds has been drawn a rising attention so far. In this review, we focus on summarizing several autophagy-associated targets, such as AMPK, mTORC1, ULK1, IMPase, LRRK2, beclin-1, TFEB, GCase, ERRα, C-Abelson, and as well as their relevant small-molecule compounds in PD models, which will shed light on a clue on exploiting more potential targeted small-molecule drugs tracking PD treatment in the near future.

Cryo-EM reveals mechanistic insights into lipid-facilitated polyamine export by human ATP13A2.

The cytoplasmic polyamine maintains cellular homeostasis by chelating toxic metal cations, regulating transcriptional activity, and protecting DNA. ATP13A2 was identified as a lysosomal polyamine exporter responsible for polyamine release into the cytosol, and its dysfunction is associated with Alzheimer's disease and other neural degradation diseases. ATP13A2 belongs to the P5 subfamily of the P-type ATPase family, but its mechanisms remain unknown. Here, we report the cryoelectron microscopy (cryo-EM) structures of human ATP13A2 under four different conditions, revealing the structural coupling between the polyamine binding and the dephosphorylation. Polyamine is bound at the luminal tunnel and recognized through numerous electrostatic and π-cation interactions, explaining its broad specificity. The unique N-terminal domain is anchored to the lipid membrane to stabilize the E2P conformation, thereby accelerating the E1P-to-E2P transition. These findings reveal the distinct mechanism of P5B ATPases, thereby paving the way for neuroprotective therapy by activating ATP13A2.

Structural mechanisms for gating and ion selectivity of the human polyamine transporter ATP13A2.

Mutations in ATP13A2, also known as PARK9, cause a rare monogenic form of juvenile-onset Parkinson's disease named Kufor-Rakeb syndrome and other neurodegenerative diseases. ATP13A2 encodes a neuroprotective P5B P-type ATPase highly enriched in the brain that mediates selective import of spermine ions from lysosomes into the cytosol via an unknown mechanism. Here we present three structures of human ATP13A2 bound to an ATP analog or to spermine in the presence of phosphomimetics determined by cryoelectron microscopy. ATP13A2 autophosphorylation opens a lysosome luminal gate to reveal a narrow lumen access channel that holds a spermine ion in its entrance. ATP13A2's architecture suggests physical principles underlying selective polyamine transport and anticipates a "pump-channel" intermediate that could function as a counter-cation conduit to facilitate lysosome acidification. Our findings establish a firm foundation to understand ATP13A2 mutations associated with disease and bring us closer to realizing ATP13A2's potential in neuroprotective therapy.

Heterozygous GBA D409V and ATP13a2 mutations do not exacerbate pathological α-synuclein spread in the prodromal preformed fibrils model in young mice.

Autophagic dysregulation and lysosomal impairment have been implicated in the pathogenesis of Parkinson's disease, partly due to the identification of mutations in multiple genes involved in these pathways such as GBA, SNCA, ATP13a2 (also known as PARK9), TMEM175 and LRRK2. Mutations resulting in lysosomal dysfunction are proposed to contribute to Parkinson's disease by increasing α-synuclein levels, that in turn may promote aggregation of this protein. Here, we used two different genetic models-one heterozygous for a mutated form of the GBA protein (D409V), and the other heterozygous for an ATP13a2 loss-of-function mutation, to test whether these mutations exacerbate the spread of α-synuclein pathology following injection of α-synuclein preformed fibrils in the olfactory bulb of 12-week-old mice. Contrary to our hypothesis, we found that mice harboring GBA D409V+/- and ATP13a2+/- mutations did not have exacerbated behavioral impairments or histopathology (α-synuclein, LAMP2, and Iba1) when compared to their wildtype littermates. This indicates that in the young mouse brain, neither the GBA D409V mutation or ATP13a2 loss-of-function mutation accelerate the spread of α-synuclein pathology. As a consequence, we postulate that these mutations increase Parkinson's disease risk only by acting in one of the initial, upstream events in the Parkinson's disease pathogenic process. Further, the mutations, and the molecular pathways they impact, appear to play a less important role once the pathogenic process has been triggered and therefore do not specifically influence α-synuclein pathology spread.

Targeting of Lysosomal Pathway Genes for Parkinson's Disease Modification: Insights From Cellular and Animal Models.

Previous genetic studies on hereditary Parkinson's disease (PD) have identified a set of pathogenic gene mutations that have strong impacts on the pathogenicity of PD. In addition, genome-wide association studies (GWAS) targeted to sporadic PD have nominated an increasing number of genetic variants that influence PD susceptibility. Although the clinical and pathological characteristics in hereditary PD are not identical to those in sporadic PD, α-synuclein, and LRRK2 are definitely associated with both types of PD, with LRRK2 mutations being the most frequent cause of autosomal-dominant PD. On the other hand, a significant portion of risk genes identified from GWAS have been associated with lysosomal functions, pointing to a critical role of lysosomes in PD pathogenesis. Experimental studies have suggested that the maintenance or upregulation of lysosomal activity may protect against neuronal dysfunction or degeneration. Here we focus on the roles of representative PD gene products that are implicated in lysosomal pathway, namely LRRK2, VPS35, ATP13A2, and glucocerebrosidase, and provide an overview of their disease-associated functions as well as their cooperative actions in the pathogenesis of PD, based on the evidence from cellular and animal models. We also discuss future perspectives of targeting lysosomal activation as a possible strategy to treat neurodegeneration.

ATP13A2 levels in serum and cerebrospinal fluid in patients with idiopathic Parkinson's disease.

BACKGROUND: The enzyme ATP13A2 holds promise as biomarker in Parkinson's disease (PD). No study has examined the content of ATP13A2 in serum and cerebrospinal fluid (CSF) in idiopathic PD cohorts, or how ATP13A2 relates to the clinical features of the disease. METHODS: ATP13A2 concentration was evaluated with ELISA and immunoblotting. Correlations of serum and CSF ATP13A2 with clinical parameters were examined. The antiparkinsonian medication regimen was expressed as levodopa equivalent dose (LED, mg/day). RESULTS: Serum ATP13A2 concentration was similar in patients and controls, and it correlated with LED and MDS-UPDRS part-IV score (p < .0001), a scale which allows evaluating motor complications. LED also correlated with MDS-UPDRS part-IV score (p < .0001). Serum ATP13A2 concentration and LED were higher in patients with motor complications than in patients without motor complications (p < .0001). The ratio of serum ATP13A2 concentration versus LED was calculated, and mean value was similar in patients with or without motor complications. ATP13A2 concentration in the CSF was undetectable in many subjects because the ELISA assay was hampered by its detection limit. Immunoblotting indicated that CSF ATP13A2 content was higher in patients relative to controls (p = .0002), and no clinical correlations were found. CONCLUSIONS: Increasing LED enhanced serum ATP13A2 concentration and facilitated the development of motor complications. There is a direct relationship between serum ATP13A2 level and the dose intensity of the antiparkinsonian dopaminergic medication. The associations between serum ATP13A2 and LED suggest that serum ATP13A2 content might be a marker of dopamine replacement therapy.