GAS6 is a key homeostatic immunological regulator of host-commensal interactions in the oral mucosa

Maria Nassar, Yaara Tabib, Tal Capucha, Gabriel Mizraji, Tsipora Nir, Meirav Pevsner-Fischer, Gili Zilberman-Schapira, Oded Heyman, Gabriel Nussbaum, Herve Bercovier, Asaf Wilensky, Eran Elinav, Tal Burstyn-Cohen, Avi Hai Hovav*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

57 Scopus citations

Abstract

The oral epithelium contributes to innate immunity and oral mucosal homeostasis, which is critical for preventing local inflammation and the associated adverse systemic conditions. Nevertheless, the mechanisms by which the oral epithelium maintains homeostasis are poorly understood. Here, we studied the role of growth arrest specific 6 (GAS6), a ligand of the TYRO3-AXL-MERTK (TAM) receptor family, in regulating oral mucosal homeostasis. Expression of GAS6 was restricted to the outer layers of the oral epithelium. In contrast to protein S, the other TAM ligand, which was constitutively expressed postnatally, expression of GAS6 initiated only 3-4 wk after birth. Further analysis revealed that GAS6 expression was induced by the oral microbiota in a myeloid differentiation primary response gene 88 (MyD88)-dependent fashion. Mice lacking GAS6 presented higher levels of inflammatory cytokines, elevated frequencies of neutrophils, and up-regulated activity of enzymes, generating reactive nitrogen species. We also found an imbalance in Th17/Treg ratio known to control tissue homeostasis, as Gas6-deficient dendritic cells preferentially secreted IL-6 and induced Th17 cells. As a result of this immunological shift, a significant microbial dysbiosis was observed in Gas6-/- mice, because anaerobic bacteria largely expanded by using inflammatory byproducts for anaerobic respiration. Using chimeric mice, we found a critical role for GAS6 in epithelial cells in maintaining oral homeostasis, whereas its absence in hematopoietic cells synergized the level of dysbiosis. We thus propose GAS6 as a key immunological regulator of host-commensal interactions in the oral epithelium.

Original languageAmerican English
Pages (from-to)E337-E346
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number3
DOIs
StatePublished - 17 Jan 2017

Bibliographical note

Funding Information:
This work was supported by United States-Israel Binational Science Foundation Grant 2015209 (to A.-H.H.), and Israel Science Foundation Grant 1764/12 (to T.B.-C.).

Keywords

  • GAS6
  • Homeostasis
  • Microbiota
  • Oral mucosa
  • TAM

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