Extracellular group A Streptococcus induces keratinocyte apoptosis by dysregulating calcium signalling.
Group A Streptococcus (GAS) colonizes the oropharynx and damaged skin. To cause local infection or severe invasive syndromes the bacteria must gain access into deeper tissues. Host cell death may facilitate this process. GAS internalization has been identified to induce apoptosis. We now report an alternate mechanism of GAS-mediated apoptosis of primary human keratinocytes, initiated by extracellular GAS and involving dysregulation of intracellular calcium to produce endoplasmic reticulum stress. Two bacterial virulence factors are required for effective induction of apoptosis by extracellular GAS: (i) hyaluronic acid capsule that inhibits bacterial internalization and (ii) secreted cytolysin, streptolysin O (SLO), that forms transmembrane pores that permit extracellular calcium influx into the cytosol. Induction of keratinocyte apoptosis by wild-type GAS was accompanied by cell detachment and loss of epithelial integrity, a phenomenon not observed with GAS deficient in capsule or SLO. We propose that cell signalling initiated by extracellular GAS compromises the epithelial barrier by inducing premature keratinocyte differentiation and apoptosis, thereby facilitating GAS invasion of deeper tissues.
Cywes Bentley
Colette
C
Channing Laboratory, Brigham and Women's Hospital, Boston, MA 02115, USA. ccywes@channing.harvard.edu
Hakansson
Anders
A
Christianson
Jennifer
J
Wessels
Michael R
MR
D017209:Apoptosis; D016667:Bacterial Capsules / Q000502:physiology; D001426:Bacterial Proteins / Q000633:toxicity; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002460:Cell Line; D003593:Cytoplasm / Q000648:ultrastructure; D053938:DNA Fragmentation; D004721:Endoplasmic Reticulum / Q000648:ultrastructure; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D015603:Keratinocytes / Q000166:cytology* / Q000382:microbiology*; D008928:Mitochondria / Q000502:physiology / Q000648:ultrastructure; D010539:Permeability; D013297:Streptococcus pyogenes / Q000378:metabolism / Q000472:pathogenicity*; D013301:Streptolysins / Q000633:toxicity; D014617:Vacuoles / Q000648:ultrastructure
D001426:Bacterial Proteins; D001896:Boron Compounds; D018960:Hyaluronan Receptors; D013301:Streptolysins; C025964:streptolysin O; C109986:2-aminoethoxydiphenyl borate; D002118:Calcium