Group A streptococcal M protein activates the NLRP3 inflammasome

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Updated: Feb 25, 2026

Activation and Measurement of NLRP3 Inflammasome Activity Using IL-1β in Human Monocyte-derived Dendritic Cells
09:04

Activation and Measurement of NLRP3 Inflammasome Activity Using IL-1β in Human Monocyte-derived Dendritic Cells

Published on: May 22, 2014

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J Andrés Valderrama1,2, Angelica M Riestra1, Nina J Gao1

  • 1Department of Pediatrics, University of California, San Diego, La Jolla, CA, 92093, USA.

Nature Microbiology
|August 9, 2017
PubMed

Insights

Released M1 protein from Group A Streptococcus (GAS) causes macrophage pyroptosis via NLRP3 inflammasome activation. This IL-1β release may warn of infection but can also worsen tissue injury during systemic GAS disease.

Area of Science:

  • Immunology
  • Microbiology
  • Molecular Biology

Background:

  • Group A Streptococcus (GAS) causes significant human mortality.
  • M1 serotype GAS strains are linked to severe invasive infections.
  • M protein is the most abundant GAS surface protein.

Purpose of the Study:

  • To investigate the role of soluble M1 protein in macrophage cell death.
  • To elucidate the mechanism of M1-induced inflammasome activation.
  • To understand the dual role of M1 protein in host immune response.

Main Methods:

  • Studied M1 protein's effect on macrophage programmed cell death.
  • Investigated caspase-1-dependent NLRP3 inflammasome activation.
  • Analyzed M1 protein internalization via clathrin-mediated endocytosis.
  • Utilized mouse intraperitoneal challenge models.

Main Results:

  • Soluble M1 protein triggers macrophage pyroptosis and IL-1β release.
  • M1 acts as a second signal for NLRP3 inflammasome activation.
  • The M1 B-repeat domain is crucial for inflammasome activation, K+ efflux, and M1 internalization.
  • M1 specifically activates IL-1β in vivo, acting as an immune warning.

Conclusions:

  • M1 protein directly induces macrophage pyroptosis and IL-1β release.
  • M1-mediated hyperinflammation can exacerbate tissue damage in systemic GAS infections.
  • Soluble M1 protein plays a complex role in host defense and pathogenesis.

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