The Parkinson-associated human P5B-ATPase ATP13A2 modifies lipid homeostasis.

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). However, the genetic spectrum of ATP13A2-associated disorders was expanded in the last years, because it has been found to underlay variants of neuronal ceroid-lipofuscinoses (NCLs) and hereditary spastic paraplegia. As ATP13A2 seems to be a key component of the endo-lysosome pathway, the fact that these pathologies are commonly characterized by endo-lysosomal dysfunction is not surprising. Here we report that increasing the level of functional ATP13A2 in a stable SH-SY5Y cell line disrupts lipid homeostasis. ATP13A2 overexpression increases the fluorescence intensity of the fluorescent analog phosphatidylethanolamine (NBD-PE) and the formation of multilamellar bodies, resembling the so-called "drug-induced phospholipidosis". We also found that expression of ATP13A2 reduces the ceramide-fluorescence intensity and the content of bis(monoacylglyceryl)phosphate (BMP). BMP is required for lipid degradation and exosome biogenesis inside acidic compartments, so this result suggests that ATP13A2 may be modifying the lipid digestion capacity and/or the redistribution of lipids in these subcellular organelles. In addition, ATP13A2-overexpression decreased the total content of triglycerides (TGs), cholesterol and lipid droplets. As TGs are necessary for the synthesis of new membranes, this observation suggests that increasing the function of ATP13A2 switches the endo-lysosomal system towards vesicle secretion.

Sphingosine kinase and sphingosine-1-phosphate regulate epithelial cell architecture by the modulation of de novo sphingolipid synthesis.

Sphingolipids regulate several aspects of cell behavior and it has been demonstrated that cells adjust their sphingolipid metabolism in response to metabolic needs. Particularly, sphingosine-1-phosphate (S1P), a final product of sphingolipid metabolism, is a potent bioactive lipid involved in the regulation of various cellular processes, including cell proliferation, cell migration, actin cytoskeletal reorganization and cell adhesion. In previous work in rat renal papillae, we showed that sphingosine kinase (SK) expression and S1P levels are developmentally regulated and control de novo sphingolipid synthesis. The aim of the present study was to evaluate the participation of SK/S1P pathway in the triggering of cell differentiation by external hypertonicity. We found that hypertonicity evoked a sharp decrease in SK expression, thus activating the de novo sphingolipid synthesis pathway. Furthermore, the inhibition of SK activity evoked a relaxation of cell-cell adherens junction (AJ) with accumulation of the AJ complex (E-cadherin/ß-catenin/α-catenin) in the Golgi complex, preventing the acquisition of the differentiated cell phenotype. This phenotype alteration was a consequence of a sphingolipid misbalance with an increase in ceramide levels. Moreover, we found that SNAI1 and SNAI2 were located in the cell nucleus with impairment of cell differentiation induced by SK inhibition, a fact that is considered a biochemical marker of epithelial to mesenchymal transition. So, we suggest that the expression and activity of SK1, but not SK2, act as a control system, allowing epithelial cells to synchronize the various branches of sphingolipid metabolism for an adequate cell differentiation program.

CHO cells expressing the human P5-ATPase ATP13A2 are more sensitive to the toxic effects of herbicide paraquat.

P-ATPases are membrane transporters energized by ATP. The subfamily of P5-ATPases is the least studied P-ATPases and the ion substrate specificity of the P5 subfamily is not known. Mutations of the human P5ATPase gene ATP13A2 has been shown to underlie a form of Parkinson disease (PD). We investigated the link between ATP13A2 and environmental factors related to PD development. Increasing concentrations of the synthetic polyamine analog paraquat induced a greater cytotoxic effect over CHO cells expressing ATP13A2. Paraquat-toxicity was associated with increased production of cellular reactive oxygen species and this increment was reversed by the natural polyamine spermidine. Acridine orange fluorescence intensity suggested that ATP13A2 induced the expansion of acidic vesicles that become more alkaline upon external addition of spermidine. Polyamine uptake is proposed to be initiated by a plasma membrane carrier followed by sequestration into acidic vesicles of the late endocytic compartment through an unidentified active mechanism; because ATP13A2 is located in lysosomes and late endosomes, our results open the possibility that ATP13A2 could be one of those active transporters capable of transporting polyamines like spermidine as well as its toxic analog paraquat.