K2.1 channels modulate the pH- and mechanosensitivity of pancreatic stellate cells.

Pancreatic stellate cells (PSCs) are central in the development of acute pancreatitis and tumor fibrosis in pancreatic ductal adenocarcinoma (PDAC). Fibrosis and a unique pH landscape represent characteristic properties of the PDAC microenvironment. Mechanosensitive ion channels are involved in the activation of PSCs. Among these channels, K2.1 has not yet been studied in PSCs. K2.1 channels are pH- and mechanosensitive. We confirmed K2.1 expression in PSCs by RT-qPCR and immunofluorescence. PSCs from K2.1 and K2.1 mice were studied under conditions mimicking properties of the PDAC microenvironment (acidic extracellular pH (pH), ambient pressure elevated by + 100 mmHg). Migration and the cell area were taken as surrogates for PSC activation and evaluated with live cell imaging. pH-dependent changes of the membrane potential of PSCs were investigated with DiBAC(3), a voltage-sensitive fluorescent dye. We observed a correlation between morphological activation and progressive hyperpolarization of the cells in response to changes in pH and pressure. The effect was in part dependent on the expression of K2.1 channels because the membrane potential of K2.1 PSCs was always more hyperpolarized than that of K2.1 PSCs. Cell migration velocity of K2.1 cells decreased upon pressure application when cells were kept in an acidic medium (pH 6.6). This was not the case in K2.1 PSCs. Taken together, our study highlights the critical role of K2.1 channels in the combined sensing of environmental pressure and pH by PSCs and in coordinating cellular morphology with membrane potential dynamics. Thus, K2.1 channels are important mechano-sensors in murine PSCs.