Abstract
Previously, we showed that the overexpression of ORAI1 calcium channel in neurons of murine brain led to spontaneous occurrence of seizure-like events in aged animals of transgenic line FVB/NJ-Tg(ORAI1)Ibd (Nencki Institute of Experimental Biology). We aimed to identify the mechanism that is responsible for this phenomenon. Using a modified Ca2+-addback assay in the CA1 region of acute hippocampal slices and FURA-2 acetomethyl ester (AM) Ca2+ indicator, we found that overexpression of ORAI1 in neurons led to altered Ca2+ response. Next, by RNA sequencing (RNAseq) we identified a set of genes, whose expression was changed in our transgenic animals. These data were validated using customized real-time PCR assays and digital droplet PCR (ddPCR) ddPCR. Using real-time PCR, up-regulation of hairy and enhancer of split-5 (Hes-5) gene and down-regulation of aristaless related homeobox (Arx), doublecortin-like kinase 1 (Dclk1), and cyclin-dependent kinase-like 5 (Cdkl5, also known as serine/threonine kinase 9 (Stk9)) genes were found. Digital droplet PCR (ddPCR) analysis revealed down-regulation of Arx. In humans, ARX, DCLK1, and CDLK5 were shown to be mutated in some rare epilepsy-associated disorders. We conclude that the occurrence of seizure-like events in aged mice overexpressing ORAI1 might be due to the down-regulation of Arx, and possibly of Cdkl5 and Dclk1 genes.
Highlights
Store operated calcium entry (SOCE) is a well-described process in non-excitable cells
The expression profile of all three homologues of ORAI varies in different tissues, with the highest level of ORAI1 in immune cells [25] and ORAI2 in the brain [26], whereas ORAI3 is abundant in many solid organs and its enhanced gene expression is reported in cancerous cells [27]
It is well established that local Ca2+ microdomains that appear upon opening of store operated calcium channels activate downstream effectors like calcineurin or adenylyl cyclase in non-excitable cells
Summary
Store operated calcium entry (SOCE) is a well-described process in non-excitable cells. Reduction in [Ca2+]ER results in activation of plasma membrane Ca2+ channels that mediate sustained Ca2+ influx, which is required for a variety of processes. They include maintaining Ca2+ oscillations [10], mitochondrial fatty acid oxidation [11], refilling of Ca2+ stores, and a few other [12]. These manipulations resulted in altered neuronal excitability [23] All of these studies have shown that homoand heteromeric CRAC channels demonstrate different SOCE response, which indicates the importance of the stoichiometry of different ORAI homologues that form the CRAC channel. Patients with inherited null or loss of function mutations in ORAI1 suffer from severe combined immunodeficiency-like disease that is accompanied with chronic, often lethal infections and a variety of non-immunological symptoms [30,31]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
