Sorcin Activates the Brain PMCA and Blocks the Inhibitory Effects of Molecular Markers of Alzheimer’s Disease on the Pump Activity

Since dysregulation of intracellular calcium (Ca(2+)) levels is a common occurrence in neurodegenerative diseases, including Alzheimer’s disease (AD), the study of proteins that can correct neuronal Ca(2+) dysregulation is of great interest. In previous work, we have shown that plasma membrane Ca(2+)-ATPase (PMCA), a high-affinity Ca(2+) pump, is functionally impaired in AD and is inhibited by amyloid-β peptide (Aβ) and tau, two key components of pathological AD hallmarks. On the other hand, sorcin is a Ca(2+)-binding protein highly expressed in the brain, although its mechanism of action is far from being clear. Sorcin has been shown to interact with the intracellular sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA), and other modulators of intracellular Ca(2+) signaling, such as the ryanodine receptor or presenilin 2, which is closely associated with AD. The present work focuses on sorcin in search of new regulators of PMCA and antagonists of Aβ and tau toxicity. Results show sorcin as an activator of PMCA, which also prevents the inhibitory effects of Aβ and tau on the pump, and counteracts the neurotoxicity of Aβ and tau by interacting with them.