Expression of genes encoding the calcium signalosome in cellular and transgenic models of Huntington's disease

Abstract

Huntington's disease (HD) is a hereditary neurodegenerative disease caused by the expansion of a polyglutamine stretch in the huntingtin (HTT) protein and characterized by dysregulated calcium homeostasis. We investigated whether these disturbances are correlated with changes in the mRNA level of the genes that encode proteins involved in calcium homeostasis and signaling (i.e., the calciosome). Using custom-made TaqMan low-density arrays containing probes for 96 genes, we quantified mRNA in the striatum in YAC128 mice, a model of HD, and wildtype mice. HTT mutation caused the increased expression of some components of the calcium signalosome, including calretinin, presenilin 2, and calmyrin 1, and the increased expression of genes indirectly involved in calcium homeostasis, such as huntingtin-associated protein 1 and calcyclin-binding protein. To verify these findings in a different model, we used PC12 cells with an inducible expression of mutated full-length HTT. Using single-cell imaging with Fura-2AM, we found that store-operated Ca2+ entry but not endoplasmic reticulum (ER) store content was changed as a result of the expression of mutant HTT. Statistically significant downregulation of the Orai calcium channel subunit 2, calmodulin, and septin 4 was detected in cells that expressed mutated HTT. Our data indicate that the dysregulation of calcium homeostasis correlates with changes in the gene expression of members of the calciosome. These changes, however, differed in the two models of HD used in this study. Our results indicate that each HD model exhibits distinct features that may only partially resemble the human disease.

Expression of ORAI1, a Plasma Membrane Resident Subunit of the CRAC Channel, in Rodent and Non-rodent Species

“…We confirmed this difference at the message level using ISH in the mouse using an ISH probe that is just 5' to the binding region for mAb266.1 in the protein. Northern blot of Orai1 mRNA using a probe similar to our ISH probe has also previously detected mouse brain expression (Gross et al 2007) in addition to another report using qPCR techniques (Czeredys et al 2013). Consistent with the hypothesis that there is a CNS-specific truncated form of ORAI1, ISH was performed using a probe that binds 3' to the one described in this study, as part of the Allen Brain Atlas project; no CNS expression was apparent using that probe (Sunkin et al 2013).…”

Early pridopidine treatment improves behavioral and transcriptional deficits in YAC128 Huntington disease mice

“…Inspection of the 19 DEGs annotated as being enriched in cholinergic neurons revealed that, while their pattern of expression is similar between the 10 mg/kg and 30 mg/kg groups, the magnitude of change in level of expression (relative to the YAC128 vehicle group) was dose dependent, i.e., greater in the 30 mg/kg compared with the 10 mg/kg group ( Figure 7C). Of note, a number of these genes have been previously implicated in HD, such as Cib2 (35), Npas1 (36), St8sia2 (37), and Gng4 (38). Our results suggest that the dose effects seen in the behavioral assays were associated with underlying differential transcriptional patterns and that they further implicate synaptic changes and the cholinergic system in the greater functional improvements seen with the 30 mg/kg pridopidine dose.…”

“…Four of the DEGs identified in the cell type-specific expression analysis, namely Cib2, Npas1, St8sia2, and Gng4, have been previously linked to HD: Cib2, a calcium and integrin-binding family member, is upregulated in the striata of YAC128 HD mice as well as in a PC12 model of HD (35); levels of Npas1, a neuronal PAS domain protein 1 thought to be involved in chromatin remodelling and transcription, are elevated in the PC12 model of HD (36); St8sia2, a ST8 α-N-acetyl-neuraminide α-2,8-Sialyltransferase 2 related to ganglioside biosynthesis, has been reported to be decreased in the R6/1 mouse model of HD (37); levels of Gng4, a brain-specific subunit of heterotrimeric G protein suggested to play a role in presynaptic function of kainate receptors (62,63), are elevated in D1 medium spiny neurons of YAC128 HD mice at 13 and 23 months of age (44). Our analysis not only validated these previous findings, but also showed that pridopidine treatment (30 mg/kg) reverses the HD-related alterations in the levels of these genes.…”

AMPA Receptors Are Involved in Store-Operated Calcium Entry and Interact with STIM Proteins in Rat Primary Cortical Neurons

“…Recently, SOCE in neurons has become the subject of intense research with regard to disturbances in Ca 2+ homeostasis that are observed in several neurological disorders, including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, chronic epilepsy, amyotrophic lateral sclerosis, painful nerve injury and cerebral ischemia (Leissring et al, 2000; Berna-Erro et al, 2009; Steinbeck et al, 2011; Wu et al, 2011; Czeredys et al, 2013; Kawamata et al, 2014). Because of the high expression of STIM2 in the brain (Berna-Erro et al, 2009; Skibinska-Kijek et al, 2009), lower sensitivity of STIM2 to ER Ca 2+ store depletion, and slower oligomerization rate of STIM2 compared with STIM1 (Stathopulos et al, 2009; Hoth and Niemeyer, 2013), STIM2 appears to be the major player in the nervous system.…”