Myosin-II mediated traction forces evoke localized Piezo1-dependent Ca(2+) flickers.

Cells, including human neural stem cells, live in three dimensional environments that provide physical and mechanical stimuli. We now understand that these mechanical forces are potent regulators of cell function. Stem cells have multiple ways of sensing mechanical signals, but a recently discovered primary means of interpreting these cues is through channels, or pores, on the cell surface. In particular, Piezo channels transduce mechanical stimuli into electrical and chemical signals to powerfully influence development, tissue homeostasis, and regeneration. Studies on Piezo1 have largely focused on transduction of "outside-in" mechanical forces, or external forces applied to cells. However, Piezo1 response to internal, cell-generated forces remains poorly understood. Here, using measurements of Piezo1 activity and cell-generated traction forces in native human neural stem cell conditions, we show that cellular forces cause Piezo1-mediated Ca(2+) flickers, which are rapid movements of calcium through the pore in the plasma membrane, in precise locations in the cell. Although Piezo1 channels move around the cell surface easily and are widely distributed across the cell, the flicker activity is enriched near force-producing zones of attachment in the cells. The mechanical force that activates Piezo1 arises from recruitment of a motor protein called Myosin in cells that moves along linear tracks to generate force. We propose that Piezo1 Ca(2+) flickers allow precise localization of mechanical sensing in human neural stem cells, and that movement along the cell surface allows Piezo1 channels to explore a large number of mechanical microdomains and thus respond to a greater diversity of mechanical cues.