Inhibition of MCF-7 breast cancer cell proliferation by a synthetic peptide derived from the C-terminal sequence of Orai channel.

Intracellular Ca2+ signals play many important cellular functions such as migration, proliferation and differentiation. Store-operated Ca2+ entry (SOCE) is a major route of Ca2+ entry in nonexcitable cells. The activation of SOCE requires engagement between stromal interaction molecule 1 (STIM1) molecules on the endoplasmic reticulum and Ca2+ release-activated Ca2+ (CRAC) channel Orais (Orai1-3) on the plasma membrane. Accumulating evidence indicates that SOCE plays critical roles in cancer cell proliferation, invasion and metastasis. Here, we used the synthetic intracellular peptides derived from the C-termini of Orai channels to treat the breast cancer cells. We have found that Orai3-CT peptide exhibits stronger binding to STIM1 than Orai1-CT, and Orai3-CT peptide acts in a dominant negative fashion, blocking the STIM1-Orai1 interaction and reducing the Ca2+ entry and proliferation of breast cancer cells. Schematic model for Orai peptide inhibiting the proliferation of breast cancer cells. SOAR domain of STIM1 binding to CT and NT of Orai1 leads to the channel opened and calcium entry. The synthetic intracellular peptides derived from Orai channels competitive interact with STIM1, blocking the STIM1-Orai1 interaction and calcium entry, thus reducing the activation of Ca2+-dependent transcription factors and inhibiting the proliferation of breast cells. Image 1 [ABSTRACT FROM AUTHOR]