Journal Article

Expression of Pls (Plasmin Sensitive) in Staphylococcus aureus Negative for pls Reduces Adherence and Cellular Invasion and Acts by Steric Hindrance

Muzaffar  Hussain, Daniel  Schäfer, Katri M.  Juuti, Georg  Peters, Bettina  Haslinger‐Löffler, Pentti I.  Kuusela and Bhanu  Sinha

in The Journal of Infectious Diseases

Published on behalf of Infectious Diseases Society of America

Volume 200, issue 1, pages 107-117
Published in print July 2009 | ISSN: 0022-1899
Published online July 2009 | e-ISSN: 1537-6613 | DOI: https://dx.doi.org/10.1086/599359
Expression of Pls (Plasmin Sensitive) in Staphylococcus aureus Negative for pls Reduces Adherence and Cellular Invasion and Acts by Steric Hindrance

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Background. The methicillin‐resistant Staphylococcus aureus (MRSA) surface protein Pls (plasmin sensitive) reduces adhesion to host proteins and cellular invasiveness by an unknown mechanism that requires Pls expression. Here, we tested the effect of Pls expression using different pls‐negative backgrounds.

Methods. Three pls‐negative strains (the methicillin‐susceptible Staphylococcus aureus strains Cowan I and 6850 and the MRSA strain ST239‐635/93, which harbors staphylococcal cassette chromosome [SCC] mec type III) were transformed. Constructs used were full‐length pls (pPLS4), pls‐ΔLPDTG (no sortase motif; pPLS5), and pls‐ΔSD (no serine–aspartic acid [SD] repeats; pPLS6). Adherence, invasiveness, gene expression, and surface expression were quantified by photometry, flow cytometry, real‐time reverse‐transcription polymerase chain reaction, and a modified enzyme‐linked immunosorbent assay, respectively.

Results. In Pls‐expressing strains (those with pPLS4), adherence to immobilized fibronectin (Fn) and binding of soluble Fn was reduced by ∼20% and ∼25%, respectively. Invasion of 293 cells and EA.hy 926 cells was reduced by up to 85%. Surprisingly, transcription of fnbA and spa was up‐regulated, but transcription of clfA and hla was down‐regulated. Pls and Fn‐binding protein (FnBP) surface expression was increased. Competition with purified FnBPA, but not with Pls, reduced invasiveness by ∼90%. The invasiveness of 6850 (pPLS5) and of 6850 (pPLS6) was reduced by only ∼20% and ∼15%, respectively.

Conclusion. Expression of cell wall–anchored Pls reduces adherence and invasiveness independently of the MRSA/SCCmec background. This occurs despite early up‐regulation of fnbA transcription and FnBP surface expression. Thus, Pls acts by steric hindrance rather than another mechanism.

Journal Article.  5877 words.  Illustrated.

Subjects: Infectious Diseases ; Immunology ; Public Health and Epidemiology ; Microbiology

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