Lithium Sensitive ORAI1 Expression, Store Operated Ca2+ Entry and Suicidal Death of Neurons in Chorea-Acanthocytosis

Lisann Pelzl,Mohamed Jemaà,Florian Lang,Rosi Bissinger,Ludger Schöls,Christos Stournaras,Itishri Sahu,Yogesh Singh,Basma Sukkar,Philip Höflinger,Bhaeldin Elsir,Stefan Hauser

doi:10.1038/s41598-017-06451-1

Abstract

Chorea-Acanthocytosis (ChAc), a neurodegenerative disorder, results from loss-of-function-mutations of chorein-encoding gene VPS13A. In tumour cells chorein up-regulates ORAI1, a Ca2+-channel accomplishing store operated Ca2+-entry (SOCE) upon stimulation by STIM1. Furthermore SOCE could be up-regulated by lithium. The present study explored whether SOCE impacts on neuron apoptosis. Cortical neurons were differentiated from induced pluripotent stem cells generated from fibroblasts of ChAc patients and healthy volunteers. ORAI1 and STIM1 transcript levels and protein abundance were estimated from qRT-PCR and Western blotting, respectively, cytosolic Ca2+-activity ([Ca2+]i) from Fura-2-fluorescence, as well as apoptosis from annexin-V-binding and propidium-iodide uptake determined by flow cytometry. As a result, ORAI1 and STIM1 transcript levels and protein abundance and SOCE were significantly smaller and the percentage apoptotic cells significantly higher in ChAc neurons than in control neurons. Lithium treatment (2 mM, 24 hours) increased significantly ORAI1 and STIM1 transcript levels and protein abundance, an effect reversed by inhibition of Serum & Glucocorticoid inducible Kinase 1. ORAI1 blocker 2-APB (50 µM, 24 hours) significantly decreased SOCE, markedly increased apoptosis and abrogated the anti-apoptotic effect of lithium. In conclusion, enhanced neuronal apoptosis in ChAc at least partially results from decreased ORAI1 expression and SOCE, which could be reversed by lithium treatment.

Highlights

Chorein is expressed in a wide variety of tissues[11,12,13] and participates in the regulation of diverse functions including dopamine release[14], platelet activation[13], cytoskeletal architecture[15], endothelial cell stiffness[12], and tumour cell survival[3]
In order to test whether the pathophysiology of chorea-acanthocytosis (ChAc) involves deranged neuronal regulation of the Ca2+ release activated Ca2+ channel ORAI1 and/or its regulator STIM1, experiments were performed with neurons generated from induced pluripotent stem cells
ORAI1 and STIM1 transcript levels and protein abundance. qRT-PCR was utilized for the quantification of the transcript levels encoding ORAI1 or STIM1

Summary

Introduction

Chorein is expressed in a wide variety of tissues[11,12,13] and participates in the regulation of diverse functions including dopamine release[14], platelet activation[13], cytoskeletal architecture[15], endothelial cell stiffness[12], and tumour cell survival[3]. The present study explored whether chorein deficiency and lithium impact on neuronal ORAI1 expression, SOCE and/or cell survival. To this end skin fibroblasts from ChAc patients and age-matched healthy individuals were reprogrammed and differentiated to neurons and ORAI transcript levels, ORAI protein abundance, SOCE and apoptosis determined without or with prior lithium treatment

Methods

Results

Conclusion