The dual M protein systems have diverse biological characteristics, but both contribute to M18-type Group A Streptococcus pathogenicity

• Published in: Microbes and infection 2023-08, p.105209-105209, Article 105209
• Main Authors: Zhou, Xiaorui, Song, Haoshuai, Pan, Fei, Yuan, Chen, Jia, Lu, Wu, Bing, Fan, Hongjie, Ma, Zhe
• Format: Article
• Language: English
• Subjects: Bacterial pathogenicity; Biological characteristics; Group A Streptococcus; M protein
• ISSN: 1286-4579; 1769-714X
• DOI: 10.1016/j.micinf.2023.105209

M protein is a key surface virulence factor in Group A Streptococcus (GAS), Group C Streptococcus (GCS), and other streptococcal species. GAS encodes M protein using the emm gene, while GCS employs the szm (or sem) gene. In M18-type GAS, dual M protein systems exist, comprising both GAS and GCS M proteins (encoded separately by emm18 and spa18). The spa18 gene in M18-type GAS shares a conserved region highly similar to GCS's szm gene. Our study reveals that spa18 exhibits higher transcription levels than emm18 in M18-type GAS strains. The dual M protein systems defective mutant (Δemm18Δspa18) displays a smooth surface, whereas wild-type and single M protein gene mutants remain rough. M18 and SPA18 proteins possess distinct characteristics, showing varied binding properties and cytotoxicity effects on macrophages (THP-1) and keratinocytes (HaCaT). Both emm18 and spa18 genes contribute to the skin pathogenicity of M18-type GAS. Transcriptome analysis suggests the potential involvement of the mga gene in spa18 transcription regulation, while SpyM18_2047 appears to be specific to spa18 regulation. In summary, this research offers a crucial understanding of the biological characteristics of dual M protein systems in M18-type GAS, highlighting their contributions to virulence and transcriptional regulation.