A role for the Stentor syntaxin protein in post-wound cell survival.

Wound repair is an essential biological process that occurs both in tissues and single cells. In free-living, single-celled ciliates such as Stentor coeruleus, rapid repair from wounds is necessary to heal breaches to the plasma membrane, where any delays represent the difference between life and death. To discover novel molecular pathways that are important for healing in Stentor, we carried out a targeted RNA interference-based perturbation genetic screen combined with microsurgical wounding using a microfluidic guillotine to introduce reproducible bisection wounds. We identified a Stentor syntaxin gene that was necessary for cell survival, particularly post-wounding, with only ∼37% of syntaxin-deficient cells surviving compared with ∼98% of control cells. Syntaxin-deficient cells were more susceptible to hypoosmotic shock and became increasingly vacuolated in the hours post-wounding, eventually leading to cell death. Wounding of the cells in 75 mM sorbitol during and after bisection partially restored post-wound survival in knockdown cells. These results support the interpretation that syntaxin-deficient cells lack essential membrane fusion machinery, which manifests in vacuolar defects, and are deficient in maintaining osmotic homeostasis necessary for their survival post-wounding. This study provides a template for the discovery of new wound healing biology in emerging model systems.