Mechanical stretch regulates macropinocytosis in Hydra vulgaris

Abstract

Cells rely on a diverse array of engulfment processes to sense, exploit, and adapt to their environments. Among these, macropinocytosis enables indiscriminate and rapid uptake of large volumes of fluid and membrane, rendering it a highly versatile engulfment strategy. Much of the molecular machinery required for macropinocytosis has been well established, yet how this process is regulated in the context of organs and organisms remains poorly understood. Here, we report the discovery of extensive macropinocytosis in the outer epithelium of the cnidarian Hydra vulgaris. Exploiting Hydra’s relatively simple body plan, we developed approaches to visualize macropinocytosis over extended periods of time, revealing constitutive engulfment across the entire body axis. We show that the direct application of planar stretch leads to calcium influx and the inhibition of macropinocytosis. Finally, we establish a role for stretch-activated channels in inhibiting this process. Together, our approaches provide a platform for the mechanistic dissection of constitutive macropinocytosis in physiological contexts and highlight a potential role for macropinocytosis in responding to cell surface tension.

Abstract

• Macropinocytosis is a versatile endocytic strategy involved in nutrient acquisition, immune surveillance, and membrane remodeling. Despite extensive molecular characterization, much remains unknown about the regulation of macropinocytosis in tissues.

• The authors report a previously undescribed form of constitutive macropinocytosis in the epithelium of Hydra and reveal a role for tissue stretch in regulating this process.

• Our findings suggest that constitutive macropinocytosis may be more pervasive than previously appreciated and highlight a potential role for this biological phenomenon in membrane tensioning and tissue remodeling.