A natural variant of the cysteine protease virulence factor of group A Streptococcus with an arginine-glycine-aspartic acid (RGD) motif preferentially binds human integrins α _v β ₃ and α _IIb β ₃

Abstract

The human pathogenic bacterium group A Streptococcus produces an extracellular cysteine protease [streptococcal pyrogenic exotoxin B (SpeB)] that is a critical virulence factor for invasive disease episodes. Sequence analysis of the speB gene from 200 group A Streptococcus isolates collected worldwide identified three main mature SpeB (mSpeB) variants. One of these variants (mSpeB2) contains an Arg-Gly-Asp (RGD) sequence, a tripeptide motif that is commonly recognized by integrin receptors. mSpeB2 is made by all isolates of the unusually virulent serotype M1 and several other geographically widespread clones that frequently cause invasive infections. Only the mSpeB2 variant bound to transfected cells expressing integrin ␣ v ␤ 3 (also known as the vitronectin receptor) or ␣ IIb ␤ 3 (platelet glycoprotein IIb-IIIa), and binding was blocked by a mAb that recognizes the streptococcal protease RGD motif region. In addition, mSpeB2 bound purified platelet integrin ␣ IIb ␤ 3 . Defined ␤ 3 mutants that are altered for fibrinogen binding were defective for SpeB binding. Synthetic peptides with the mSpeB2 RGD motif, but not the RSD sequence present in other mSpeB variants, blocked binding of mSpeB2 to transfected cells expressing ␣ v ␤ 3 and caused detachment of cultured human umbilical vein endothelial cells. The results (i) identify a Gram-positive virulence factor that directly binds integrins, (ii) identify naturally occurring variants of a documented Gram-positive virulence factor with biomedically relevant differences in their interactions with host cells, and (iii) add to the theme that subtle natural variation in microbial virulence factor structure alters the character of hostpathogen interactions.Group A Streptococcus (GAS) is a human pathogenic bacterium that causes diverse infections ranging in severity from relatively mild pharyngitis to life-threatening toxic shock syndrome and necrotizing fasciitis (1). GAS is composed of a heterogeneous array of chromosomal genotypes, and substantial levels of allelic variation also exist in genes encoding putative and proven virulence factors that mediate hostpathogen interactions (2-5). With the exception of M protein, whose structural variation helps GAS evade the type-specific immune response of the host (6), there has been little investigation of the potential ramifications of GAS allelic variation for host-pathogen interactions.GAS isolates produce a highly conserved extracellular cysteine protease known as streptococcal pyrogenic exotoxin B (SpeB) (reviewed in ref. 5). SpeB is initially expressed as a 40-kDa zymogen but then is converted to a 28-kDa active protease by proteolytic truncation (5, 7). SpeB is a critical virulence factor in two mouse models of invasive disease (8, 38) and human infections (5). Purified SpeB causes a cytopathic effect on cultured human endothelial cells (3) and has been shown to activate a host matrix metalloprotease (9).Integrins are heterodimeric membrane proteins located on the surface of mammalian cells that participate in ce...

Structure of the streptococcal endopeptidase IdeS, a cysteine proteinase with strict specificity for IgG

“…In addition, IdeS is not affected by the typical cysteine proteinase inhibitor E-64 (4,6), which is in sharp contrast to the described prokaryotic cysteine proteinases (16)(17)(18)(19), and suggests a unique catalytic property of IdeS. Like the classical streptococcal cysteine proteinase, SpeB (streptococcal pyrogenic exotoxin B), IdeS contains an RGD motif (4,14,15), which is involved in the interaction of IdeS with vitronectin (␣ V␤3 ) and platelet receptors (␣ II␤3 ) (21), suggesting additional, yet unknown properties of the enzyme. Thus, IdeS represents an atypical cysteine proteinase with unique biochemical features, suggesting that the enzyme might represent an additional family of cysteine proteinases.…”

“…Additionally, IdeS contains an RGD motif at amino acids 214-216, which is located on a surface loop within the L domain as a turn connecting ␤4 and ␤5. This motif is important for recognition by integrins and is also present in the streptococcal cysteine proteinase SpeB (streptococcal pyrogenic exotoxin B) (14,21).…”

“…Extracellular bacterial cysteine proteinases have also been characterized from other pathogenic bacteria such as Clostridium histolyticum, Porphyromonas gingivalis, and Staphylococcus aureus (2). These cysteine proteinases exhibit broad substrate specificity and are consequently expressed as proenzymes, requiring proteolytic processing to convert into their mature forms (7)(8)(9)(10)(11)(12)(13)(14).…”

A Role of Arginine Deiminase From Streptococcus Pyogenes M49-16 in Promoting Infection and Inhibition of Endothelial Cell Proliferation

“…Это выражается в нарушении процесса коагуляции, снижении адгезивности эндотели-альных клеток и повышении проницаемости эн-дотелиального барьера [1]. Описанные эффекты связывают с индукцией экспрессии на эндотели-альных клетках тканевого фактора и активацией матриксных металлопротеаз [4,5,19]. Эндоте-лиальные клетки экспрессирует еNOS и аргина-зу -ферменты, субстратом для которых является аргинин, поэтому метаболиты аргинина играют важную роль в регуляции функций эндотелия сосудов.…”

Group A Streptococcus: allelic variation, population genetics, and host-pathogen interactions

“…One common theme revealed by large-scale analysis of virulence gene variation is that several mechanisms have contributed to generating allelic diversity in natural populations of GAS, including point mutations, slipped-strand mispairing, and assortive recombination (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19).…”