A lipid switch unlocks Parkinson’s disease-associated ATP13A2

Abstract

ATP13A2 is a lysosomal P-type transport ATPase that has been implicated in Kufor-Rakeb syndrome and Parkinson's disease (PD), providing protection against α-synuclein, Mn 2+ , and Zn 2+ toxicity in various model systems. So far, the molecular function and regulation of ATP13A2 remains undetermined. Here, we demonstrate that ATP13A2 contains a unique N-terminal hydrophobic extension that lies on the cytosolic membrane surface of the lysosome, where it interacts with the lysosomal signaling lipids phosphatidic acid (PA) and phosphatidylinositol(3,5)bisphosphate [PI(3,5)P2]. We further demonstrate that ATP13A2 accumulates in an inactive autophosphorylated state and that PA and PI(3,5)P2 stimulate the autophosphorylation of ATP13A2. In a cellular model of PD, only catalytically active ATP13A2 offers cellular protection against rotenone-induced mitochondrial stress, which relies on the availability of PA and PI(3,5)P2. 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.mitochondria | lysosome | flippase | α-synuclein | P5-type ATPase N euronal fitness depends on optimal lysosomal function and efficient lysosomal delivery of proteins and organelles by autophagy for subsequent breakdown (1, 2). Kufor-Rakeb syndrome (KRS) is an autosomal recessive form of Parkinson's disease (PD) associated with dementia, which is caused by mutations in ATP13A2/PARK9 (3). Mutations in or knockdown (KD) of ATP13A2 lead to lysosomal dysfunctions, including reduced lysosomal acidification, decreased degradation of lysosomal substrates (4), impaired autophagosomal flux (4, 5), and accumulation of fragmented mitochondria (5, 6). By contrast, overexpression (OE) of Ypk9p (i.e., the yeast ATP13A2 ortholog) protects yeast against toxicity of α-synuclein (7), which is the major protein in Lewy bodies, the abnormal protein aggregates that develop inside nerve cells in PD. 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+ (7-9) and Zn 2+ (10-12), it was proposed that ATP13A2 may function as a Mn 2+ (7-9) and/or Zn 2+ transporter (10-12).ATP13A2 belongs to the P5 subfamily of the P-type ATPase superfamily, which comprises five subfamilies (P1-5) of membrane transporters. P-type ATPases hydrolyze ATP to actively transport inorganic ions across membranes or lipids between membrane leaflets (reviewed in ref. 13). During the transport cycle, a phosphointermediate is formed on a conserved aspartate residue (14). The human P5-type ATPases are divided into two groups, P5A (ATP13A1) and P5B (ATP13A2-5), but their transport specificity has not been established (14-16).P-type ATPases comprise a membrane-embedded core of six transmembrane (TM) helices (M1-6) that form the substrate binding site(s) and entrance/exit pathways for the transp...

Unlocking ATP13A2/PARK9 activity

“…The cellular functions of PI (3,5)P2 might partially relate to ATP13A2, since loss of ATP13A2 results in neurodegeneration, an increased lysosomal pH and impaired autophagy. 2 We further show that ATP13A2 mediates protection against rotenone-induced mitochondrial stress requiring both catalytic activity of ATP13A2 and the lipids PA and PI (3,5)P2. This hints to a lipiddependent activation of ATP13A2 that is important for mitochondrial homeostasis and/or clearance 2 (Fig.…”

“…However, we demonstrated that the N-terminus does not traverse the membrane, but rests on the cytosolic membrane surface of late endo-/lysosomes where it may serve as a docking platform for lipids and proteins 2 (Fig. 1).…”

“…2 PA is a conical phospholipid with a small anionic head group inducing a negative membrane curvature and promoting membrane fission and fusion. PA is also a local signaling lipid e.g.…”

“…Of interest, PLD1 regulates a-synuclein clearance via autophagy pathways, which might depend on PAmediated ATP13A2 activation. 2 The low-abundance phosphoinositide PI(3,5)P2 predominantly exists in endo-/ lysosomal compartments, functioning as an organelle tag. Mutations in the PI(3,5) P2 5-phosphatase FIG4 trigger CharcotMarie-Tooth Type 4J disease and YunisVaron syndrome, which are marked by neurodegeneration.…”

“…The presented biochemical evidence of the catalytic autophosphorylation reaction refutes any direct stimulation of activity by Zn 2C or Mn 2C , suggesting that ATP13A2 may not directly transport heavy metals. 2 Instead, the tight connection with lipids and vesicular processes rather suggests that ATP13A2 might be a putative lipid flippase, resembling the closely related P4-type lipid flippases that regulate lipid signaling and/or membrane curvature. Such a function might explain ATP13A2's pleiotropic effects on exosome release, Zn 2C and Mn 2C homeostasis and toxicity, mitochondrial clearance and a-synuclein detoxification.…”