Monomeric α‐synuclein activates the plasma membrane calcium pump

• Published in: The EMBO journal 2023-12, Vol.42 (23), p.e111122-n/a
• Main Authors: Kowalski, Antoni, Betzer, Cristine, Larsen, Sigrid Thirup, Gregersen, Emil, Newcombe, Estella A, Bermejo, Montaña Caballero, Bendtsen, Viktor Wisniewski, Diemer, Jorin, Ernstsen, Christina V, Jain, Shweta, Bou, Alicia Espiña, Langkilde, Annette Eva, Nejsum, Lene N, Klipp, Edda, Edwards, Robert, Kragelund, Birthe B, Jensen, Poul Henning, Nissen, Poul
• Format: Article
• Language: English
• Subjects: alpha‐synuclein; Binding sites; Ca2+-transporting ATPase; Calcium; Calcium homeostasis; Calcium ions; Calmodulin; Expulsion; Extrusion; Hippocampus; Homeostasis; Lipids; Mathematical models; Membranes; Neurodegeneration; Neurological disorders; Neurons; Neurotransmitter release; Phospholipids; Physiology; plasma membrane Ca2+‐ATPase; presynapse; Protein interaction; Segments; Stimulators; Synapses; Synuclein
• ISSN: 0261-4189; 1460-2075
• DOI: 10.15252/embj.2022111122

Alpha‐synuclein (aSN) is a membrane‐associated and intrinsically disordered protein, well known for pathological aggregation in neurodegeneration. However, the physiological function of aSN is disputed. Pull‐down experiments have pointed to plasma membrane Ca2+‐ATPase (PMCA) as a potential interaction partner. From proximity ligation assays, we find that aSN and PMCA colocalize at neuronal synapses, and we show that calcium expulsion is activated by aSN and PMCA. We further show that soluble, monomeric aSN activates PMCA at par with calmodulin, but independent of the autoinhibitory domain of PMCA, and highly dependent on acidic phospholipids and membrane‐anchoring properties of aSN. On PMCA, the key site is mapped to the acidic lipid‐binding site, located within a disordered PMCA‐specific loop connecting the cytosolic A domain and transmembrane segment 3. Our studies point toward a novel physiological role of monomeric aSN as a stimulator of calcium clearance in neurons through activation of PMCA. Synopsis Plasma‐membrane Ca2+‐ATPase (PMCA) is shown here to be activated by α‐synuclein (aSN) in the presence of negatively charged lipids. Colocalization of aSN and PMCA at synapses and aSN stimulated, PMCA dependent calcium extrusion indicate a role in neuronal calcium homeostasis that is supported by mathematical modeling. Cross‐linking and proximity ligation analyses show synaptic colocalization of PMCA and aSN. PMCA‐dependent calcium ion extrusion from primary hippocampal neurons is increased by aSN expression. aSN and negatively charged lipids stimulate PMCA ATPase activity to a comparable extent as calcium‐calmodulin stimulation in the presence of neutral lipids. The activation of PMCA by aSN requires the membrane‐binding N‐terminal segment of aSN and a binding site of PMCA for negatively charged lipids. Modeling suggests an important role of PMCA activation for calcium homeostasis in firing neurons. Soluble, monomeric α‐synuclein activates calcium ion release through Ca2+‐ATPase.