Role of M3 protein in the adherence and internalization of an invasive Streptococcus pyogenes strain by epithelial cells

Osnat Eyal, Jeries Jadoun, Arcady Bitler, Ehud Skutelski, Shlomo Sela

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8 Scopus citations


Streptococcus pyogenes utilizes multiple mechanisms for adherence to and internalization by epithelial cells. One of the molecules suggested of being involved in adherence and internalization is the M protein. Although strains of the M3 serotype form the second largest group isolated from patients with severe invasive diseases and fatal infections, not much information is known regarding the interactions of M3 protein with mammalian cells. In this study we have constructed an emm3 mutant of an invasive M3 serotype (SP268), and demonstrated that the M3 protein is involved in both adherence to and internalization by HEp-2 cells. Fibronectin promoted both adherence and internalization of SP268 in an M3-independent pathway. Utilizing speB and speB/emm3 double mutants, it was found that M3 protein is not essential for the maturation of SpeB, as was reported for the M1 protein. Increased internalization efficiency observed in both the speB and emm3/speB mutants suggested that inhibition of S. pyogenes internalization by SpeB is not related to the presence of an intact M3 protein. Thus, other proteins in SP268, which serve as targets for SpeB activity, have a prominent role in the internalization process.

Original languageEnglish
Pages (from-to)205-213
Number of pages9
JournalFEMS Immunology and Medical Microbiology
Issue number3
StatePublished - 15 Oct 2003
Externally publishedYes

Bibliographical note

Funding Information:
We thank Dr. N. Koren-Moreg for her assistance in statistical analysis. This study was supported in part by grant No. 3754 from the Chief Scientist’s Office of the Ministry of Health, Israel, and by a grant from the Israel Science Foundation awarded to S.S.


  • Adherence
  • Capsule
  • Cysteine protease
  • Group A streptococcus
  • HEp-2
  • Internalization
  • M protein
  • SpeB


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