# Bioinorganic Explorations of Host-defense Proteins

> **NIH NIH R01** · MASSACHUSETTS INSTITUTE OF TECHNOLOGY · 2024 · $314,422

## Abstract

PROJECT SUMMARY
The overarching goal of this renewal application is to elucidate the molecular basis for how human calprotectin
(CP, S100A8/S100A9 oligomer) functions in the metal-withholding innate immune response, and to evaluate its
impact on the physiology of uropathogenic Escherichia coli (UPEC), which cause the majority of urinary tract
infections in humans. Transition metals are essential nutrients for all organisms, and the availability of these
nutrients plays a critical role during microbial infection. Consequently, the human innate immune system
launches a metal-withholding response and deploys metal-sequestering host-defense proteins into the
extracellular space to limit metal availability and hinder pathogen growth. CP is an abundant and functionally
versatile metal-withholding protein; it sequesters multiple metal nutrients including Mn(II), Fe(II), Ni(II) and
Zn(II). Recent studies by our laboratory and others provide compelling evidence that the molecular speciation
of extracellular CP is a heterogenous ensemble of different species that arises from different metal-bound
forms as well as oxidative post-translational modifications. We hypothesize that this complex molecular
speciation of CP, including the occurrence of methionine oxidation and disulfide bonding, has profound
consequences for its extracellular function and lifetime. Recent studies by our laboratory and others also
demonstrate that CP is a Cu-withholding protein. We hypothesize that CP sequesters both Cu(II) and Cu(I) and
that this function impacts the physiology and metal homeostasis in diverse bacterial pathogens including
UPEC. In Aim 1, we will examine disulfide bond formation within and between CP heterodimers, the
biophysical properties of these disulfide-linked species, and their ability to sequester metals from bacterial
pathogens. In Aim 2, we will evaluate the Cu(II/I)-binding properties of CP and the consequences of multi-
metal sequestration by CP on UPEC as a case study. We expect that these investigations will advance the
molecular model for how CP contributes to the metal-sequestering innate immune response, underscore the
importance of considering CP species that result from oxidative posttranslational modification, and elucidate
the molecular basis for Cu withholding by CP. Moreover, we expect that our studies of the interplay of CP and
UPEC will provide new insight into how the host and pathogen compete for Cu and other nutrient metals. We
further expect that the outcomes of this initiative may guide the design and development of novel diagnostic,
preventative and therapeutic approaches for microbial infections and other pathologies such as inflammatory
diseases that involve CP.

## Key facts

- **NIH application ID:** 10892941
- **Project number:** 5R01GM118695-07
- **Recipient organization:** MASSACHUSETTS INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** ELIZABETH M NOLAN
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $314,422
- **Award type:** 5
- **Project period:** 2017-08-15 → 2026-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10892941

## Citation

> US National Institutes of Health, RePORTER application 10892941, Bioinorganic Explorations of Host-defense Proteins (5R01GM118695-07). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10892941. Licensed CC0.

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