Piezo, Nephrocyte Function, and Slit Diaphragm Maintenance in Drosophila.

BACKGROUND The Piezo gene encodes a highly conserved cell membrane protein responsible for sensing pressure. The glomerular kidney and the slit diaphragm filtration structure depend on pressure for filtration. However, how Piezo is involved in kidney function and in maintaining the slit diaphragm filtration structure is not clear. METHODS We used Drosophila pericardial nephrocytes, filtration kidney cells with striking structural and functional similarities to human podocytes, in a loss-of-function model (mutant and knockdown) to study the roles of Piezo in nephrocyte filtration and function. RESULTS Piezo is highly expressed at the invaginated membranes (lacuna channels) of nephrocytes. A Piezo loss-of-function mutant showed significant nephrocyte functional decline. Nephrocyte-specific silencing of Piezo showed disruption of the slit diaphragm filtration structure and significant functional defects. Electron microscopy showed that silencing Piezo in nephrocytes leads to reduced slit diaphragm density and abnormal shape of lacuna channels. Moreover, the Piezo-deficient nephrocytes showed internalized slit diaphragm component proteins, reduced autophagy, increased ER stress, and reduced calcium influx. CONCLUSIONS Together, our findings suggest that Piezo plays an important role in the calcium homeostasis of nephrocytes and is required for maintaining nephrocyte function and the slit diaphragm filtration structure.