Both Orai1 and TRPC1 are Involved in Excessive Store-Operated Calcium Entry in Striatal Neurons Expressing Mutant Huntingtin Exon 1

Abstract

It has been previously reported that N-terminus of mutant huntingtin (product of the 1st exon) is sufficient to cause a Huntington's disease (HD) pathological phenotype. In view of recent data suggesting that improper regulation of store-operated calcium (SOC) channels is involved in neurodegenerative processes, we investigated influence of expression of the mutant huntingtin N-terminal fragment (Htt138Q-1exon) on SOC entry (SOCE) in mouse neuroblastoma cells (Neuro-2a) and in primary culture of medium spiny neurons (MSNs) isolated from mice. The results show that SOCE in these cells is enhanced upon lentiviral expression of the Htt138Q-1exon. Moreover, we demonstrated that RNAi-mediated knockdown of TRPC1, Orai1, or STIM1 proteins leads to dramatic reduction of abnormal SOCE in both Neuro-2a and MSNs, expressing Htt138Q-1exon. Thus, we concluded that abnormal SOCE in these cells is maintained by both TRPC1- and Orai1-containing channels and required STIM1 for its activation. Furthermore, EVP4593 compound previously tested as a potential anti-HD drug in a Drosophila screening system has proved to be capable of reducing SOCE to the normal level in MSNs expressing the Htt138Q-1exon.

Direct Activation of NADPH Oxidase 2 by 2-Deoxyribose-1-Phosphate Triggers Nuclear Factor Kappa B-Dependent Angiogenesis

“…In our study, NOX2 activation by dRP leads to NF-κB activation (as shown by several approaches, including p65-NF-κB translocation and phosphorylation), which appears critical in the proangiogenic signaling cascade triggered by dRP. The role of NF-κB in the signaling cascade stimulated by dRP was demonstrated using both the QNZ inhibitor [which not only has low nanomolar potency on NF-κB but can also inhibit store-operated calcium channels at high nanomolar concentrations ( 68 )] and genetic silencing of p65-NF-κB. This is in agreement with recent studies showing activation of NF-κB downstream of NOX2 in angiogenic responses of endothelial cells ( 40 ).…”

Store-Operated Calcium Entries Control Neural Stem Cell Self-Renewal in the Adult Brain Subventricular Zone

“…In accordance, the Orai1 gene has been reported as one of the six candidate genes that could be responsible of the neurological phenotypes found in inherited microdeletion syndromes caused by a 445 kb chromosomal deletion [66]. Also, defective SOCE have been associated to severe brain disorders where stem cell dysfunctions have been reported like neurodegenerative Alzheimer's disease [67][68][69]. Conversely, increased SOC and STIM expression occurs in brain cancer cells that could arise from mutated NSC [70][71][72][73].…”

Huntington’s Disease: Calcium Dyshomeostasis and Pathology Models

“…EVP4593 exerted a similar effect on MSN cells expressing an N-terminal fragment of mHtt [16]. Now, EVP4593 is proven to act as an inhibitor of SOCE necessary for the initial stages of the NF-κB signaling pathways; however, the molecular target of EVP4593 remains unknown.…”

“…Cytofluorimetric measurements demonstrated that incubation of Neuro-2a cells (HD model) with EVP4593 results in increased survival of the cells [16]. …”