The remodelling and degradation of extracellular matrix collagen by fibroblasts involves phagocytosis. Here, cell membrane extensions of the fibroblast engulf the collagen fibril with the help of the subcortical actin network. Actin-binding proteins, such as flightless-1 (Fli1) and its interactor non-muscle myosin IIA (NMMIIA), may contribute to generate contraction forces. Currently, it is unclear how Fli1−NMMIIA-activity is initiated to form cell extensions. In this issue (p. 2196), Pamma Arora and co-workers look at the role of Ca2+ for cell extensions and collagen remodelling. They observe high Ca2+ influx at fibroblast extension sites and strong expression of the Ca2+-permeable transient receptor potential vanilloid-4 (TRPV4) channel, which also localizes to cell adhesion sites. Chemical inhibition of TRPV4 or downregulation of TRPV4 prevent Ca2+ influx and interaction of Fli1 with NMMIIA, which reduces cell extensions and blocks collagen remodelling. The authors show in pull-down experiments that loss of Ca2+ prevents the interaction between Fli1 and NMMIIA, and use fluorescence resonance energy transfer to demonstrate the need of Ca2+ influx for Fli1−NMMIIA activity in cells. This work establishes that the Fli1−NMMIIA interaction is controlled by Ca2+ influx through TRPV4 channels, thereby enabling fibroblasts to form extensions that are necessary for phagocytosis of extracellular matrix collagen.