A quantitative Streptococcus pyogenes–human protein–protein interaction map reveals localization of opsonizing antibodies

Abstract

A fundamental challenge in medical microbiology is to characterize the dynamic protein–protein interaction networks formed at the host–pathogen interface. Here, we generate a quantitative interaction map between the significant human pathogen, Streptococcus pyogenes , and proteins from human saliva and plasma obtained via complementary affinity-purification and bacterial-surface centered enrichment strategies and quantitative mass spectrometry. Perturbation of the network using immunoglobulin protease cleavage, mixtures of different concentrations of saliva and plasma, and different S. pyogenes serotypes and their isogenic mutants, reveals how changing microenvironments alter the interconnectivity of the interaction map. The importance of host immunoglobulins for the interaction with human complement proteins is demonstrated and potential protective epitopes of importance for phagocytosis of S. pyogenes cells are localized. The interaction map confirms several previously described protein–protein interactions; however, it also reveals a multitude of additional interactions, with possible implications for host–pathogen interactions involving other bacterial species.

High-sensitivity assessment of phagocytosis by persistent association-based normalization

“…To our knowledge the impact of how interacting with one prey affects subsequent interactions with additional prey, has not been studied for phagocytosis; Hill coefficient analysis would offer a guide of where to start to look for such studies. The PAN method is especially valuable when looking at different bacterial mutants or strains that would affect surface properties (Happonen et al, 2019), and thus potentially directly affect persistent association. A key aspect that should be emphasized is that the MOP curves not only serve as an analysis in itself, but can also provide a guide to the dynamic range of the system, and at which MOP more detailed analysis, such as microscopy, should be performed, to improve sensitivity and potentially save unnecessary experimental set up time.…”

Structural determination ofStreptococcus pyogenesM1 protein interactions with human immunoglobulin G using integrative structural biology

“…To cause invasive infections, GAS expresses a wide range of virulence factors to evade human defense mechanisms. These virulence factors mostly consist of secreted or surface-associated proteins that target proteins and protein complexes of the innate and adaptive immune systems [3,4,5]. Specifically, GAS expresses several IgG degrading enzymes [6,7,8] and Fc-binding proteins [9,10,11] that target immunoglobulins G (IgGs), key players of the humoral immune response.…”

“…In the family of M proteins, antigenic variation has resulted in more than 200 serotypes, but only a few are frequently associated with invasive disease, with M1 being the most prevalent serotype [14]. Moreover, to physically protect its vulnerable antigenic epitopes, GAS scavenges human plasma proteins to form a surrounding coat-like barrier [4,15,13], and among these interactions specifically binds IgG-molecules via their Fc-domains rendering these inaccessible for Fc-receptors [16].…”

“…Among these interactions, the M1-IgG binding is found to be environment-specific, binding via Fab-domains under antibody-rich conditions such as plasma, or via Fc-domains in an antibody-poor environment such as saliva [16]. We have previously shown that all human IgG subclasses can bind to the M1 protein [4]; however, the molecular details of these interactions are not fully understood.…”

Immunization With a Secreted Esterase Protects Mice Against Multiple Serotypes (M1, M3, and M28) of Group A Streptococcus

“…Streptococcus pyogenes also called Group A Streptococcus (GAS), can produce an arsenal of extracellular secreted proteins to evade the innate immune system (Walker et al, 2014;Hynes and Sloan, 2016;Liu and Lei, 2018;Happonen et al, 2019). Although treated with modern medicine, it remains a significant cause of global morbidity and mortality (Dickson et al, 2018;Hua et al, 2019;Lynskey et al, 2019).…”