Orai1 Channel Regulates Human-Activated Pancreatic Stellate Cell Proliferation and TGF(β1) Secretion through the AKT Signaling Pathway

SIMPLE SUMMARY: Activated pancreatic stellate cells (aPSCs), the main source of cancer-associated fibroblasts in pancreatic ductal adenocarcinoma (PDAC), are well known as the key actor of the abundant fibrotic stroma development surrounding the tumor cells. In permanent communication with the tumor cells, they enhance PDAC early spreading and limit the drug delivery. However, the understanding of PSC activation mechanisms and the associated signaling pathways is still incomplete. In this study, we aimed to evaluate the role of Ca(2+), and Orai1 Ca(2+) channels, in two main PSC activation processes: cell proliferation and cytokine secretion. Indeed, Ca(2+) is a versatile second messenger implicated in the regulation of numerous biological processes. We believe that a better comprehension of PSC Ca(2+) -dependent activation mechanisms will bring up new crucial PDAC early prognostic markers or new targeting approaches in PDAC treatment. ABSTRACT: Activated pancreatic stellate cells (aPSCs), the crucial mediator of pancreatic desmoplasia, are characterized, among others, by high proliferative potential and abundant transforming growth factor (β1) (TGF(β1)) secretion. Over the past years, the involvement of Ca(2+) channels in PSC pathophysiology has attracted great interest in pancreatic cancer research. We, thus, aimed to investigate the role of the Orai1 Ca(2+) channel in these two PSC activation processes. Using the siRNA approach, we invalided Orai1 expression and assessed the channel functionality by Ca(2+) imaging, the effect on aPSC proliferation, and TGF(β1) secretion. We demonstrated the functional expression of the Orai1 channel in human aPSCs and its implication in the store-operated Ca(2+) entry (SOCE). Orai1 silencing led to a decrease in aPSC proliferation, TGF(β1) secretion, and AKT activation. Interestingly, TGF(β1) induced a higher SOCE response by increasing Orai1 mRNAs and proteins and promoted both AKT phosphorylation and cell proliferation, abolished by Orai1 silencing. Together, our results highlight the role of Orai1-mediated Ca(2+) entry in human aPSC pathophysiology by controlling cell proliferation and TGF(β1) secretion through the AKT signaling pathway. Moreover, we showed a TGF(β1)-induced autocrine positive feedback loop by promoting the Orai1/AKT-dependent proliferation via the stimulation of Orai1 expression and function.