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

Wound healing is an essential biological process that occurs both in tissues and single cells. In free-living single-celled ciliates such as Stentor coeruleus, rapid wound healing is necessary to repair breaches to the plasma membrane, where any delays represent the difference between life and death. In order 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 the syntaxin-deficient cells surviving compared with [~]98% of the control cells. Syntaxin-deficient cells were more susceptible to hyposmotic shock and became increasingly vacuolated in the hours post-wounding, eventually leading to cell death. Osmotic stabilization of the cells during and after bisection partially restored the 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. SignificanceO_LIStentor is a single-celled ciliate with prodigious healing ability, yet the molecular mechanisms by which the cell rapidly heals wounds are not fully characterized. C_LIO_LIThrough a targeted microfluidics genetic screen, we identified a novel syntaxin-like protein that is essential for Stentor survival post-wounding. C_LIO_LISyntaxin-deficient cells were more susceptible to osmotic shock. Wounding cells in osmotically balanced conditions reduced the degree of hyposmotic stress associated with wounding and enabled more cells to survive. Our discovery highlights the rebalancing of intracellular osmolarity as an important step in wound repair in freshwater-dwelling organisms. C_LI