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TRPC1‐STIM1 Activation Modulates Transforming Growth Factor β‐induced Epithelial‐to‐Mesenchymal Transition
Author(s) -
Schaar Anne,
Sukumaran Pramod,
Sun Yuyang,
Dhasarathy Archana,
Singh Brij
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.lb91
Subject(s) - epithelial–mesenchymal transition , microbiology and biotechnology , stim1 , trpc1 , chemistry , endoplasmic reticulum , cadherin , transforming growth factor , extracellular , biology , receptor , transient receptor potential channel , cell , downregulation and upregulation , biochemistry , gene
Objective Tumor metastasis is the principal cause of cancer‐associated deaths; therefore, identifying the mechanism(s) of Epithelial‐to‐Mesenchymal Transition (EMT) mediated metastasis, including the role of the ubiquitous second messenger Ca2+, is important to limit cancer induced death. Activation of Epithelial‐to‐Mesenchymal Transition (EMT) is important for tumor metastasis to occur. Although growth factors such as TGFβ and EGF have been shown to induce EMT in breast epithelial cells, the mechanism resulting in migration is not well understood. TGFβ induced EMT down regulates the epithelial factors E‐cadherin and increases expression of mesenchymal neural cadherin (N‐cadherin) through a process known as the ‘cadherin switch’. Cleavage of E‐cadherin in both localized and metastatic tumors is believed to be mediated by the calcium (Ca2+)‐dependent calpain family of cysteine proteases, however the ion channel and the source of Ca2+ entry is not yet identified. Changes in intracellular Ca2+ are the result of either the release of Ca2+ stores from the endoplasmic reticulum (ER) that initiates store‐operated Ca2+ entry (SOCE) mechanism, or direct Ca2+ entry from the extracellular space upon membrane depolarization. During initiation of SOCE (when ER Ca2+ stores are depleted) Stromal Interaction Molecule 1 (STIM1) is shown to aggregate at the ER‐PM junctions, where it interacts with proteins such as the Transient Receptor Potential Canonical 1 (TRPC1) channel causing Ca2+ influx. Herein, we provide evidence that Ca2+ entry into the cell, especially upon store‐depletion, plays an important role in TGFβ‐induced EMT by promoting cellular migration and potentially leading to metastasis. The increased migration by TGFβ in non‐cancerous cells was due to the loss of E‐cadherin along with a subsequent increase in N‐cadherin levels. Importantly, TGFβ‐treatment increases store‐mediated Ca2+ entry, which was essential for the activation of calpain cleavage of E‐cadherin. Inhibition of Ca2+ entry by using non‐specific Ca2+ channel blocker SKF‐96365, significantly decreased Ca2+ entry, decreased TGFβ‐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 STIM1 significantly decreased TGFβ induced Ca2+ entry as well as inhibited TGFβ‐mediated calpain activation and cell migration. 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. Support or Funding Information Financial support was received from the National Institutes of Health (DE017102) awarded to B.B.S. and 5P20GM104360 awarded to AD.