Differential engagement of ORAI1 and TRPC1 in the induction of vimentin expression by different stimuli

Abstract

The Ca 2+ signal is essential in both hypoxia-and epidermal growth factor (EGF)-mediated epithelial to mesenchymal transition (EMT) in MDA-MB-468 breast cancer cells. This finding suggests that Ca 2+-permeable ion channels participate in the induction of expression of some mesenchymal markers such as vimentin. However, the ion channels involved in vimentin expression induction have not been fully characterized. This work sought to define how differential modulation of the calcium signal effects the induction of vimentin and the Ca 2+ influx pathways involved. We identified that the intracellular Ca 2+ chelator EGTA-AM, cytochalasin D (a modulator of cytoskeletal dynamics and cell morphology) and the sarco/endoplasmic reticulum ATPase inhibitor thapsigargin are all inducers of vimentin in MDA-MB-468 breast cancer cells. EGTA-AM-and thapsigargin-mediated induction of vimentin expression in MDA-MB-468 cells involves store-operated Ca 2+ entry, as evidenced by sensitivity to silencing of the molecular components of this pathway, STIM1 and ORAI1. In stark contrast, cytochalasin D-mediated vimentin induction was insensitive to silencing of ORAI1, despite sensitivity to silencing of its canonical activator the endoplasmic reticulum Ca 2+ sensor STIM1. Cytochalasin D-mediated vimentin induction was, however, sensitive to silencing of another reported STIM1 target, TRPC1. Subsequent studies identified that EGTA-AM-induced vimentin expression also partially involved a TRPC1-dependent pathway. These studies define a complex interplay between vimentin expression in this model and the specific Ca 2+-permeable ion channels involved. The complexity in the engagement of different Ca 2+ influx pathways that regulate vimentin induction are opportunities but also potential challenges in targeting Ca 2+ signaling to block EMT in cancer cells. Our findings further highlight the need to identify potential indispensable ion channels that can regulate induction of specific mesenchymal markers via different stimuli.

Activation of the Ion Channel TRPV4 Induces Epithelial to Mesenchymal Transition in Breast Cancer Cells

“…A variety of EMT inducers are sensitive to intracellular Ca 2+ chelation, and specific Ca 2+ permeable ion channels can regulate EMT. However, in many cases, these Ca 2+ permeable ion channels regulate only specific EMT markers and/or are specific to particular EMT inducers [7,11]. In contrast, our studies show that TRPV4 silencing and pharmacological inhibition attenuates vimentin protein induction induced by both EGF and hypoxia.…”

“…Ca 2+ signal-sensitive EMT induction has now been demonstrated in a variety of cancer cell types, including those of the ovary [8], prostate [9], and liver [10]. However, it is clearly the nature of the calcium signal that is important in EMT induction since not all stimuli that elevate [Ca 2+ ] CYT induce EMT [7], and in many cases silencing of calcium-permeable ion channels such as TRPM7, TRPC1, and ORAI1 only inhibit the induction of some EMT markers [7,11,12]. Although there are widely available pharmacological activators for calcium-permeable ion channels such as the L-type voltage-gated Ca 2+ channel activator BAYK8644 [13] and the TRPV1 activator capsaicin [14], the lack of readily available pharmacological activators for specific ion channels associated with EMT induction in cancer cells has made it difficult to fully define the role of the calcium signal in EMT.…”

Ca²⁺ Signaling and Hypoxia/Acidic Tumour Microenvironment Interplay in Tumour Progression

“…TRPC1 also promotes human glioma cancer cells' proliferation via Ca 2+ entry and supports tumour growth in vivo [139], and lung cancer differentiation, by promoting A549 cell proliferation [140]. TRPC1 also participates with ORAI1 channels in the induction of vimentin, a mesenchymal marker for epithelial-mesenchymal transition (EMT) [141] (Fig. 2 and Fig.…”

Suppression of Ca2+ signaling enhances melanoma progression

“…As discussed above (see section IIIA), many of the processes involved in focal adhesion and migration are dependent on Ca 2+ . Hence, CAMKII has been shown to phosphorylate and activate Vimentin (105) and Vimentin activation and STIM1/TRPC1dependent Ca 2+ entry has been show to increase Vimentin activity (106). Further, much of the transcriptional machinery activated during EMT is associated with Ca 2+ ; an effect that appears to be very context-dependent.…”