Streptococcus oralis and Candida albicans Synergistically Activate μ-Calpain to Degrade E-cadherin From Oral Epithelial Junctions

J Infect Dis. 2016 Sep 15;214(6):925-34. doi: 10.1093/infdis/jiw201. Epub 2016 May 13.


Streptococcus oralis forms robust mucosal biofilms with Candida albicans that have increased pathogenic potential. In this study, using oral epithelial cultures, organotypic oral mucosal constructs, and a mouse model of oral infection, we demonstrated that S. oralis augmented C. albicans invasion through epithelial junctions. C. albicans and S. oralis decreased epithelial E-cadherin levels by synergistically increasing µ-calpain, a proteolytic enzyme that targets E-cadherin. In the mouse coinfection model this was accompanied by increased fungal kidney dissemination. Coinfection with a secreted aspartyl protease (sap) mutant sap2456 and S. oralis increased μ-calpain and triggered mucosal invasion and systemic dissemination, suggesting that fungal protease activity is not required for invasion during coinfection. We conclude that C. albicans and S. oralis synergize to activate host enzymes that cleave epithelial junction proteins and increase fungal invasion.

Keywords: C. albicans; E-cadherin; S. oralis; calpain; oral mucosa; synergy.

MeSH terms

  • Animals
  • Cadherins / metabolism*
  • Calpain / metabolism*
  • Candida albicans / physiology*
  • Candidiasis, Oral / microbiology
  • Candidiasis, Oral / pathology
  • Cells, Cultured
  • Disease Models, Animal
  • Epithelial Cells / microbiology
  • Epithelial Cells / physiology
  • Female
  • Mice, Inbred C57BL
  • Microbial Interactions*
  • Proteolysis
  • Streptococcal Infections / microbiology
  • Streptococcal Infections / pathology
  • Streptococcus oralis / physiology*


  • Cadherins
  • Cdh1 protein, mouse
  • Calpain
  • mu-calpain