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ATP13A2
ATP13A2 Full Name
ATPase type 13A2
ATP13A2 Introduction
ATP13A2 (also known as PARK9) is a lysosomal transmembrane P5B-type ATPase that functions as a polyamine transporter, specifically exporting polyamines such as spermine from the lysosomal lumen into the cytosol. The gene is located on chromosome 1p36.13 and encodes a protein of approximately 130 kDa that belongs to the P-type ATPase superfamily, which typically transports cations across membranes using ATP hydrolysis. ATP13A2 is primarily localized to the lysosomes and late endosomes, where it plays critical roles in polyamine homeostasis, intracellular cation balance, autophagy regulation, and mitochondrial maintenance. Loss-of-function mutations in ATP13A2 are associated with a spectrum of neurodegenerative disorders, most notably Kufor-Rakeb syndrome (KRS), an autosomal recessive juvenile-onset form of parkinsonism, as well as early-onset Parkinson's disease (PD), neuronal ceroid lipofuscinosis, hereditary spastic paraplegia, and amyotrophic lateral sclerosis. Beyond its established role in neurodegeneration, emerging evidence has also implicated ATP13A2 in cancer biology, particularly in colorectal cancer, where it promotes tumor growth through metabolic reprogramming.
Figure 1. The molecular basis of loss-of-function mutations in the ATP13A2. (Zhang F, et al. 2022)
Gene Structure and Protein Architecture
The human ATP13A2 gene spans approximately 31 kb and contains 29 exons, with alternative splicing generating multiple transcript variants. The full-length protein consists of 1,180 amino acids and contains several structurally and functionally important domains characteristic of P5-type ATPases. The N-terminal region contains a polybasic domain that is required for targeting to late endosomes and lysosomes, as well as a membrane-embedded intramembrane domain that interacts with the lipids phosphatidic acid and phosphatidylinositol 3,5-bisphosphate, which are essential for the protective effect against mitochondrial stress. The central region contains the conserved P-type ATPase catalytic core, including the phosphorylation domain with the invariant DKTGT motif that forms the aspartyl-phosphate intermediate, the actuator domain containing the TGE motif, and the nucleotide-binding domain that binds ATP. The C-terminal region contains multiple transmembrane helices that form the channel through which polyamines are translocated. ATP13A2 also contains several conserved cysteine residues that are critical for its function and may be targets of oxidative modification. The protein exists as a monomer but may form higher-order oligomers under certain conditions, and its activity is regulated by post-translational modifications including phosphorylation and ubiquitination.
Clinical Significance: Kufor-Rakeb Syndrome and Neurodegeneration
Loss-of-function mutations in ATP13A2 cause Kufor-Rakeb syndrome (KRS), also known as PARK9, a rare autosomal recessive juvenile-onset form of parkinsonism first described in a large family from the Jordanian town of Kufor Rakeb. KRS typically presents between ages 12 and 16 years with rapid progression of clinical signs including levodopa-responsive parkinsonism (rigidity, bradyinesia, postural instability), pyramidal signs (spasticity, hyperreflexia, extensor plantar responses), supranuclear gaze palsy, cognitive decline progressing to dementia, and in some cases dystonia, myoclonus, and dysarthria. Brain MRI often reveals diffuse atrophy and bilateral hypodensity in the putamen and caudate nuclei due to iron accumulation, and dopamine transporter imaging shows reduced striatal tracer uptake, consistent with nigrostriatal dysfunction. Most patients become wheelchair-bound within 10 to 15 years of symptom onset and typically die by approximately age 30. Beyond KRS, ATP13A2 mutations have been implicated in early-onset Parkinson's disease, neuronal ceroid lipofuscinosis (a lysosomal storage disorder), hereditary spastic paraplegia, and amyotrophic lateral sclerosis, indicating significant clinical heterogeneity. The common pathological mechanisms across these disorders include lysosomal dysfunction, impaired autophagy, mitochondrial impairment, heavy metal dyshomeostasis, and accumulation of toxic protein aggregates such as alpha-synuclein. Animal models, including Atp13a2 knockout rats and mice, recapitulate key features of KRS including motor deficits, neurodevelopmental delay, neuroinflammation, and autophagy-lysosomal pathway dysfunction, providing valuable tools for understanding disease mechanisms and testing therapeutic strategies.
Alternate Names for ATP13A2
ATP13A2; ATPase type 13A2; PARK9, Parkinson disease (autosomal recessive) 9 (Kufor Rakeb syndrome); probable cation-transporting ATPase 13A2; CLN12; HSA9947; putative ATPase; KRPPD; PARK9; RP1-37C10.4; FLJ26510;
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