6786

STIM1

STIM1 is a key regulator of store-operated calcium entry (SOCE), and therefore a mediator of Ca(2)(+) entry-dependent cellular events. Phosphorylation of STIM1 at ERK1/2 target sites has been described as enhancing STIM1 activation during intracellular Ca(2)(+) emptying triggered by the inhibition of the sarco(endo)plasmic Ca(2)(+) -ATPase with thapsigargin. However, no physiological function is known for this specific phosphorylation. The present study examined the role of STIM1 phosphorylation in cell signaling triggered by EGF. Using a human endometrial adenocarcinoma cell line (Ishikawa cells) EGF or H-Ras(G12V), an active mutant of H-Ras, was found to trigger STIM1 phosphorylation at residues Ser575, Ser608, and Ser621, and this process was sensitive to PD0325901, an inhibitor of ERK1/2. Both, ERK1/2 activation and STIM1 phosphorylation took place in the absence of extracellular Ca(2)(+), indicating that both events are upstream steps for Ca(2)(+)entry activation. Also, EGF triggered the dissociation of STIM1 from EB1 (a regulator of microtubule plus-ends) in a manner similar to that reported for the activation of STIM1 by thapsigargin. Migration of the Ishikawa cells was impaired when STIM1 phosphorylation was targeted by Ser-to-Ala substitution mutation of ERK1/2 target sites. This effect was also observed with the Ca(2)(+) channel blocker SKF96365. Phosphomimetic mutation of STIM1 restored the migration to levels similar to that found for STIM1-wild type. Finally, the increased vimentin expression and relocalization of E-cadherin triggered by EGF were largely inhibited by targeting STIM1 phosphorylation, while STIM1-S575E/S608E/S621E normalized the profiles of these two EMT markers.CI - Copyright (c) 2014 Elsevier B.V. All rights reserved.

The importance of store-operated Ca(2+) entry (SOCE) and the role of its key molecular regulators, STIM1 and ORAI1, in the development of cancer are emerging. Here, we report an unexpected dual function of SOCE in prostate cancer progression by revealing a decrease in the expression of STIM1 in human hyperplasia and tumor tissues of high histological grade and by demonstrating that STIM1 and ORAI1 inhibit cell growth by arresting the G0/G1 phase and enhancing cell senescence in human prostate cancer cells. In addition, STIM1 and ORAI1 inhibited NF-kappaB signaling and remodeled the tumor microenvironment by reducing the formation of M2 phenotype macrophages, possibly creating an unfavorable tumor microenvironment and inhibiting cancer development. However, STIM1 also promoted cell migration and the epithelial-to-mesenchymal transition by activating TGF-beta, Snail and Wnt/beta-Catenin pathways. Thus, our study revealed novel regulatory effects and the mechanisms by which STIM1 affects cell senescence, tumor migration and the tumor microenvironment, revealing that STIM1 has multiple functions in prostate cancer cells.

Activation of epithelial-to-mesenchymal transition (EMT) is important for tumor metastasis. Although growth factors such as TGFbeta and EGF have been shown to induce EMT in breast epithelial cells, the mechanism resulting in migration is not well understood. Herein, we provide evidence that Ca2+ entry into the cell, especially upon store-depletion, plays an important role in TGFbeta-induced EMT by promoting cellular migration and potentially leading to metastasis. The increased migration by TGFbeta in non-cancerous cells was due to the loss of E-cadherin along with a subsequent increase in N-cadherin levels. Importantly, TGFbeta-treatment increases store-mediated Ca2+ entry, which was essential for the activation of calpain leading to the loss of E-cadherin and MMP activation. Inhibition of Ca2+ entry by using Ca2+ channel blocker SKF-96365, significantly decreased Ca2+ entry, decreased TGFbeta-induced calpain activation, and suppressed the loss of E-cadherin along with inhibiting cell migration. Furthermore, TRPC1 function as an endogenous Ca2+ entry channel and silencing of either TRPC1 or its activator, STIM1, significantly decreased TGFbeta induced Ca2+ entry, inhibited TGFbeta-mediated calpain activation and cell migration. In contrast, overexpression of TRPC1 showed increased Ca2+ entry and promoted TGFbeta-mediated cell migration. Moreover, increased TRPC1 expression was observed in ductal carcinoma cells. Together these results suggest that disrupting Ca2+ influx via TRPC1/STIM1 mechanism reduces calpain activity, which could restore intercellular junction proteins thereby inhibiting EMT induced motility.

The Ca(2+) sensor proteins STIM1 and STIM2 are crucial elements of store-operated calcium entry (SOCE) in breast cancer cells. Increased SOCE activity may contribute to epithelial-mesenchymal transitions (EMT) and increase cell migration and invasion. However, the roles of STIM1 and STIM2 in TGF-beta-induced EMT are still unclear. In this study, we demonstrate roles of STIMs in TGF-beta-induced EMT in breast cancer cells. In particular, STIM1 and STIM2 expression affected TGF-beta-induced EMT by mediating SOCE in MDA-MB-231 and MCF-7 breast cancer cells. The specific SOCE inhibitor YM58483 blocked TGF-beta-induced EMT, and differing effects of STIM1 and STIM2 on TGF-beta-induced EMT correlated with differing roles in SOCE. Finally, we showed that STIM2 is associated with non-store-operated calcium entry (non-SOCE) during TGF-beta-induced EMT, whereas STIM1 is not. What's more, non-SOCE have a large possibility to be ROCE. In conclusion, STIM1 and STIM2 proteins play important roles in TGF-beta-induced EMT and these effects are related to both SOCE and non-SOCE.CI - Copyright (c) 2017 Elsevier Inc. All rights reserved.