STIM1 deficiency is linked to Alzheimer’s disease and triggers cell death in SH-SY5Y cells by upregulation of L-type voltage-operated Ca(2+) entry

ABSTRACT: STIM1 is an endoplasmic reticulum protein with a role in Ca(2+) mobilization and signaling. As a sensor of intraluminal Ca(2+) levels, STIM1 modulates plasma membrane Ca(2+) channels to regulate Ca(2+) entry. In neuroblastoma SH-SY5Y cells and in familial Alzheimer’s disease patient skin fibroblasts, STIM1 is cleaved at the transmembrane domain by the presenilin-1-associated γ-secretase, leading to dysregulation of Ca(2+) homeostasis. In this report, we investigated expression levels of STIM1 in brain tissues (medium frontal gyrus) of pathologically confirmed Alzheimer’s disease patients, and observed that STIM1 protein expression level decreased with the progression of neurodegeneration. To study the role of STIM1 in neurodegeneration, a strategy was designed to knock-out the expression of STIM1 gene in the SH-SY5Y neuroblastoma cell line by CRISPR/Cas9-mediated genome editing, as an in vitro model to examine the phenotype of STIM1-deficient neuronal cells. It was proved that, while STIM1 is not required for the differentiation of SH-SY5Y cells, it is absolutely essential for cell survival in differentiating cells. Differentiated STIM1-KO cells showed a significant decrease of mitochondrial respiratory chain complex I activity, mitochondrial inner membrane depolarization, reduced mitochondrial free Ca(2+) concentration, and higher levels of senescence as compared with wild-type cells. In parallel, STIM1-KO cells showed a potentiated Ca(2+) entry in response to depolarization, which was sensitive to nifedipine, pointing to L-type voltage-operated Ca(2+) channels as mediators of the upregulated Ca(2+) entry. The stable knocking-down of CACNA1C transcripts restored mitochondrial function, increased mitochondrial Ca(2+) levels, and dropped senescence to basal levels, demonstrating the essential role of the upregulation of voltage-operated Ca(2+) entry through Ca(v)1.2 channels in STIM1-deficient SH-SY5Y cell death. KEY MESSAGES: STIM1 protein expression decreases with the progression of neurodegeneration in Alzheimer’s disease. STIM1 is essential for cell viability in differentiated SH-SY5Y cells. STIM1 deficiency triggers voltage-regulated Ca(2+) entry-dependent cell death. Mitochondrial dysfunction and senescence are features of STIM1-deficient differentiated cells. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00109-018-1677-y) contains supplementary material, which is available to authorized users.