STIM1 and Orai1 mediate CRAC channel activity and are essential for human glioblastoma invasion

Abstract

The Ca2+ sensor stromal interacting molecule 1 (STIM1) and the Ca2+ channel Orai1 mediate the ubiquitous store-operated Ca2+ entry (SOCE) pathway activated by depletion of internal Ca2+ stores and mediated through the highly Ca2+ selective, Ca2+ release-activated Ca2+ (CRAC) current. Furthermore, STIM1 and Orai1, along with Orai3, encode store-independent Ca2+ currents regulated by either arachidonate or its metabolite, leukotrieneC4. Orai channels are emerging as important contributors to numerous cell functions, including proliferation, migration, differentiation, and apoptosis. Recent studies suggest critical involvement of STIM/Orai proteins in controlling the development of several cancers, including malignancies of breast, prostate and cervix. Here, we quantitatively compared the magnitude of SOCE and the expression levels of STIM1 and Orai1 in non-malignant human primary astrocytes (HPA), and in primary human cell lines established from surgical samples of the brain tumor glioblastoma multiforme (GBM). Using Ca2+ imaging, patch clamp electrophysiology, pharmacological reagents, and gene silencing, we established that in GBM cells SOCE and CRAC are mediated by STIM1 and Orai1. We further found that GBM cells show upregulation of SOCE and increased Orai1 levels compared to HPA. The functional significance of SOCE was evaluated by studying the effects of STIM1 and Orai1 knockdown on cell proliferation and invasion. Utilizing Matrigel assays we demonstrated that in GBM, but not in HPA, downregulation of STIM1 and Orai1 caused a dramatic decrease in cell invasion. In contrast, the effects of STIM1 and Orai1 knockdown on GBM cell proliferation were marginal. Overall, these results demonstrate that STIM1 and Orai1 encode SOCE and CRAC currents and control invasion of GBM cells. Our work further supports the potential use of channels contributed by Orai isoforms as therapeutic targets in cancer.

Oncogenic K-Ras suppresses IP3-dependent Ca2+ release through remodeling of IP3Rs isoform composition and ER luminal Ca2+ levels in colorectal cancer cell lines

“…Through manipulation of these Ca 2+ signalling pathways in transformed cells, specific roles for each of these Ca 2+ sources in controlling aspects of cancer cell biology including regulation of cell proliferation, migration and death have been described (Crépin et al, 2007;Humez et al, 2004;Legrand et al, 2001;Lipskaia et al, 2009;Szatkowski et al, 2010;Yoshida et al, 2012). Altered expression of a number of Ca 2+ -handling proteins in tumour tissue has also been determined (Arbabian et al, 2012;Korosec et al, 2006;Monteith et al, 2012;Monteith et al, 2007;Motiani et al, 2013). Although these findings are suggestive of an important role of certain Ca 2+ signalling pathways in transformed cells, causality has not been demonstrated.…”

STIM and Orai proteins as novel targets for cancer therapy. A Review in the Theme: Cell and Molecular Processes in Cancer Metastasis

“…We isolated and established glial cell lines from tumor biopsies and found that Orai1 expression was consistently higher in primary GBM compared with human primary astrocyte (HPA) cells whereas STIM1 expression remained largely unaltered (69). Further, higher Orai1 expression corresponded to higher SOCE and I CRAC in GBMs.…”

“…Our group provided one of the earliest evidence demonstrating a crucial role for STIM1 and Orai1 in human GBMs (69). We isolated and established glial cell lines from tumor biopsies and found that Orai1 expression was consistently higher in primary GBM compared with human primary astrocyte (HPA) cells whereas STIM1 expression remained largely unaltered (69).…”

A Reciprocal Shift in Transient Receptor Potential Channel 1 (TRPC1) and Stromal Interaction Molecule 2 (STIM2) Contributes to Ca2+ Remodeling and Cancer Hallmarks in Colorectal Carcinoma Cells

“…STIM1 and ORAI1 underlie I CRAC and regulate glioblastoma cell proliferation, apoptosis, and invasion (15,16) and are involved in neuroblastoma proliferation as well (17). ORAI3 may form Ca 2ϩ -permeable channels with roles in breast cancer (18) and in non-small cell lung adenocarcinoma (19).…”