Stim and Orai mediate constitutive Ca2+ entry and control endoplasmic reticulum Ca2+ refilling in primary cultures of colorectal carcinoma cells

// Estella Zuccolo 1, * , Umberto Laforenza 2, * , Federica Ferulli 3, * , Giorgia Pellavio 2 , Giorgia Scarpellino 1 , Matteo Tanzi 3 , Ilaria Turin 3 , Pawan Faris 1, 4 , Angela Lucariello 5 , Marcello Maestri 6 , Dlzar Ali Kheder 1, 7 , Germano Guerra 5 , Paolo Pedrazzoli 8 , Daniela Montagna 3, 9, ** and Francesco Moccia 1, ** 1 Department of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, Pavia, Italy 2 Department of Molecular Medicine, University of Pavia, Pavia, Italy 3 Laboratory of Immunology Transplantation, Foundation IRCCS Policlinico San Matteo, Pavia, Italy 4 Department of Biology, College of Science, Salahaddin University, Erbil, Kurdistan-Region of Iraq, Iraq 5 Department of Medicine and Health Sciences “Vincenzo Tiberio”, University of Molise, Campobasso, Italy 6 Unit of General Surgery, Foundation IRCCS Policlinico San Matteo, Pavia, Italy 7 Department of Biology, University of Zakho, Zakho, Kurdistan-Region of Iraq, Iraq 8 Medical Oncology, Foundation IRCCS Policlinico San Matteo, Pavia, Italy 9 Department of Sciences Clinic-Surgical, Diagnostic and Pediatric, University of Pavia, Pavia, Italy * These authors have contributed equally to this work ** These authors share senior authorship of the manuscript Correspondence to: Francesco Moccia, email: francesco.moccia@unipv.it Daniela Montagna, email: d.montagna@smatteo.pv.it Keywords: colorectal cancer; store-operated Ca 2+ entry; Stim; Orai; proliferation Received: March 07, 2018     Accepted: June 23, 2018     Published: July 24, 2018 ABSTRACT Store-operated Ca 2+ entry (SOCE) provides a major Ca 2+ entry route in cancer cells. SOCE is mediated by the assembly of Stim and Orai proteins at endoplasmic reticulum (ER)-plasma membrane junctions upon depletion of the ER Ca 2+ store. Additionally, Stim and Orai proteins underpin constitutive Ca 2+ entry in a growing number of cancer cell types due to the partial depletion of their ER Ca 2+ reservoir. Herein, we investigated for the first time the structure and function of SOCE in primary cultures of colorectal carcinoma (CRC) established from primary tumor (pCRC) and metastatic lesions (mCRC) of human subjects. Stim1-2 and Orai1-3 transcripts were equally expressed in pCRC and mCRC cells, although Stim1 and Orai3 proteins were up-regulated in mCRC cells. The Mn 2+ -quenching technique revealed that constitutive Ca 2+ entry was significantly enhanced in pCRC cells and was inhibited by the pharmacological and genetic blockade of Stim1, Stim2, Orai1 and Orai3. The larger resting Ca 2+ influx in pCRC was associated to their lower ER Ca 2+ content as compared to mCRC cells. Pharmacological and genetic blockade of Stim1, Stim2, Orai1 and Orai3 prevented ER-dependent Ca 2+ release, thereby suggesting that constitutive SOCE maintains ER Ca 2+ levels. Nevertheless, pharmacological and genetic blockade of Stim1, Stim2, Orai1 and Orai3 did not affect CRC cell proliferation and migration. These data provide the first evidence that Stim and Orai proteins mediate constitutive Ca 2+ entry and replenish ER with Ca 2+ in primary cultures of CRC cells. However, SOCE is not a promising target to design alternative therapies for CRC.