# Elucidating the Role of a Staphylococcus aureus Glucosaminidase in the Innate Immune Response.

> **NIH NIH F31** · UNIVERSITY OF ILLINOIS AT CHICAGO · 2024 · $46,377

## Abstract

Project Summary
Staphylococcus aureus is a Gram-positive pathogen that causes a wide range of superficial and invasive
infections. An essential component of S. aureus infectivity and pathogenicity is the cell wall. Comprised of a thick
layer of peptidoglycan (PG), the cell wall not only ensures cell viability but also provides protection against
external stressors. Given its vital role in bacterial cell survival, PG is a major target of clinically relevant antibiotics.
Apart from its role as a protective barrier, S. aureus PG serves as a pathogen-associated molecular pattern that
promotes inflammation during infection. However, the full extent of pattern recognition receptors responsible for
sensing S. aureus PG and the molecular features required for recognition are not fully explored. Nevertheless,
we know that host-PG interactions can stimulate robust inflammation and production of the critical pro-
inflammatory cytokine, IL-1β. Indeed, the prior literature argues that the degree of PG recognition by immune
cells can shift the nature and duration of the IL-1β response, potentially leading to either infection clearance or
inflammatory pathology and persistence. S. aureus PG is composed of repeating disaccharide subunits that are
highly crosslinked via peptide cross-bridges. These glycans are remodeled by four hydrolases known as
glucosaminidases. Recently, our lab surveyed glucosaminidase mutants to determine how PG remodeling might
drive innate immunity. Our findings highlighted that a single enzyme, SagB, was required for S. aureus-mediated
induction of IL-1β by bone marrow-derived macrophages. Notably, a ΔsagB mutant failed to stimulate the
production of IL-1β while leaving other pro-inflammatory cytokines unaffected. Purified PG isolated from WT S.
aureus was sufficient to induce macrophage production of IL-1β, whereas PG from a ΔsagB mutant did not.
Furthermore, a ΔsagB mutant elicited reduced IL-1β in infected skin along with decreased inflammatory
pathology. In systemic infections, the ΔsagB mutant displayed attenuated virulence. Lastly, we discovered that
the SagB-mediated IL-1β response was independent of the NLRP3 inflammasome and caspase-1/11 activation,
suggesting the requirement of other caspases or proteases in PG-mediated IL-1β maturation. Based on these
findings, we hypothesize that SagB processes PG to generate specific glycans crucial for IL-1β maturation via
an NLRP3-independent process (Aim 1) and that SagB-processed PG elicits IL-1β and promotes inflammatory
pathology in vivo (Aim 2). Aim 1 will (i) determine the minimal PG component required to induce IL-1β from
macrophages, (ii) interrogate the cellular pathway PG activates to produce IL-1β, and (iii) assess the localization
of PG using cellular and immunological approaches. Aim 2 will use both systemic and skin and soft tissue
infection models to determine if SagB is required to promote inflammation and if SagB-dependent IL-1β
production is required to stimulate these re...

## Key facts

- **NIH application ID:** 10994827
- **Project number:** 1F31AI186287-01
- **Recipient organization:** UNIVERSITY OF ILLINOIS AT CHICAGO
- **Principal Investigator:** Kaelie Renee Johnson
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $46,377
- **Award type:** 1
- **Project period:** 2024-08-01 → 2027-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10994827

## Citation

> US National Institutes of Health, RePORTER application 10994827, Elucidating the Role of a Staphylococcus aureus Glucosaminidase in the Innate Immune Response. (1F31AI186287-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10994827. Licensed CC0.

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