Regulation of Intracellular Manganese Homeostasis by Kufor-Rakeb Syndrome-associated ATP13A2 Protein

Abstract

Mutations in the ATP13A2 gene are associated with KuforRakeb syndrome (KRS) and are found also in patients with various other types of parkinsonism. ATP13A2 encodes a predicted lysosomal P5-type ATPase that plays important roles in regulating cation homeostasis. Disturbance of cation homeostasis in brains is indicated in Parkinson disease pathogenesis. In this study, we explored the biological function of ATP13A2 as well as the pathogenic mechanism of KRS pathogenic ATP13A2 mutants. The results revealed that wild-type ATP13A2, but not the KRS pathogenic ATP13A2 mutants, protected cells from Mn 2؉ -induced cell death in mammalian cell lines and primary rat neuronal cultures. In addition, wild-type ATP13A2 reduced intracellular manganese concentrations and prevented cytochrome c release from mitochondria compared with the pathogenic mutants. Furthermore, endogenous ATP13A2 was up-regulated upon Mn 2؉ treatment. Our results suggest that ATP13A2 plays important roles in protecting cells against manganese cytotoxicity via regulating intracellular manganese homeostasis. The study provides a potential mechanism of KRS and parkinsonism pathogenesis.Mutations in ATP13A2 were initially identified in patients with Kufor-Rakeb syndrome (KRS), 2 an atypical form of inherited parkinsonism. KRS is characterized by juvenile-onset autosomal recessive nigro-striatal-pallidal-pyramidal neurodegeneration with clinical features of Parkinson disease (PD) plus spasticity, supranuclear upgaze paresis, and dementia (1). Homozygous and heterozygous mutations in ATP13A2 are also found in patients with various parkinsonism, including juvenile parkinsonism, young-onset PD, early-onset PD, and familial PD (2-9). ATP13A2 encodes a predicted lysosomal P5-type cationtransporting ATPase with multiple transmembrane domains. It is highly expressed in the brain, especially in the substantia nigra, the region with characteristic dopaminergic neuronal loss in PD. Ypk9, a yeast ortholog of ATP13A2, was shown to function as a manganese transporter to protect cells from excess Mn 2ϩ exposure, whereas loss of Ypk9 increases the sensitivity of yeast to Mn 2ϩ toxicity (10, 11). Previous studies have suggested that cation disturbance is involved in pathogenesis of PD neurodegeneration. Increased levels of cations, including iron and aluminum, are found in the substantial nigra of the PD patient brain (12, 13). Chronic occupational exposure to copper and/or manganese is associated with higher incidence of PD in a case-control study (14). Furthermore, excess levels of Mn 2ϩ accumulation in brains associated with occupational exposure, psychostimulant drug abuse, and liver disease result in an atypical form of parkinsonism in human (15).PD and parkinsonism are believed to be consequences of interactions between both genetic and environmental components (16,17). In this study, we aimed to explore the connection between the KRS-associated ATP13A2 genetic defect and manganese-associated toxicity. Our results show that wild-type ATP13A2 (ATP13A2WT), but not KRS-as...

A lipid switch unlocks Parkinson’s disease-associated ATP13A2

“…Although we recapitulate the cell-protective effects of ATP13A2 in conditions of Mn 2+ and Zn 2+ toxicity, our biochemical analysis indicates that in contrast to what was suggested in the literature (7)(8)(9)(10)(11)(12), ATP13A2 most likely is not a Mn 2+ or Zn 2+ transporter, as the steady-state levels of autophosphorylated ATP13A2 remain unaffected by Mn 2+ or Zn 2+ .…”

“…The catalytic turnover of P-type ATPases depends on the presence of the substrate to be transported (13). Because ATP13A2 may be a Mn 2+ (7)(8)(9) or Zn 2+ (10-12) pump, we tested whether Mn 2+ or Zn 2+ activate ATP13A2 turnover. However, the steady-state phosphorylation levels were unaffected by 100 μM MnCl 2 or ZnCl 2 , indicating that ATP13A2 is unlikely to transport Mn 2+ or Zn 2+ (Fig.…”

“…This protective effect of ATP13A2 on α-synuclein toxicity is conserved in yeast, Caenorhabditis elegans, and rat neuronal cells (7). Because ATP13A2 imparts resistance to Mn 2+ (7)(8)(9) and Zn 2+ (10)(11)(12), it was proposed that ATP13A2 may function as a Mn 2+ (7)(8)(9) and/or Zn 2+ transporter (10)(11)(12).…”

Shadows of an Absent Partner

“…This dependence of the GFP-Spf1 ATPase with Mg 2ϩ is similar to that of other P-ATPases where Mg 2ϩ acts as cofactor. A recent study has shown that the human P5B-ATPase ATP13A2 plays a role in regulating the intracellular manganese concentration (22). Fig.…”

Direct Comparison of Manganese Detoxification/Efflux Proteins and Molecular Characterization of ZnT10 Protein as a Manganese Transporter

“…Of the proteins postulated to be involved in manganese detoxification/efflux, the Golgi-localized secretory pathway Ca 2ϩ -ATPase 1 (SPCA1), which is an ortholog of S. cerevisiae Pmr1p, is comparatively well charac-terized (15)(16)(17). Moreover, ATP13A2/PARK9 (hereafter ATP13A2) is involved in manganese detoxification (18) based on the observation that the S. cerevisiae ortholog Ypk9p protects cells from toxicity of manganese and other metals by vacuolar sequestration (19,20). Importantly, loss-of-function mutations of the ATP13A2 gene were identified to cause an autosomal recessive form of early-onset parkinsonism (KuforRakeb syndrome) (21).…”