Transition metal ions are essential nutrients for all organisms. The availability of these nutrients plays a critical role in the host-microbe interaction and microbial pathogenesis. The primary objective of this research proposal is to elucidate how the host-defense protein calprotectin (CP) sequesters transition metals from microbes and thereby contributes to the innate immune response. CP provides a remarkable example of unique biological coordination chemistry that is relevant to infectious disease and microbial pathogenesis. Each CP heterodimer (S100A8/S100A9) exhibits six different sites for chelating divalent cations, including calcium (Ca) and transition metals. Our central hypothesis is that CP responds to physiological Ca(II) gradients to tune its coordination chemistry for transition metals and to modulate its biological function as an antimicrobial protein that deprives invading pathogens of essential nutrient metals (e.g. manganese, iron, zinc). The proposed investigations are based on preliminary data that Ca(II) binding by human CP (hCP) at the EF- hand domains triggers high-affinity chelation of transition metals at sites formed at the interface of the S100A8 and S100A9 subunits.
In Aim 1, we will investigate how Ca(II) ions modulate hCP structure and tune its affinities for transition metals.
In Aim 2, we will evaluate how the murine orthologue (mCP) sequesters transition metals and thereby provide needed molecular and biophysical insights into literature results of CP from animal models of infection.
In Aim 3, we will investigate the competition between CP and bacterial metal- transport machinery for manganese(II). These fundamental bioinorganic and biophysical initiatives constitute an innovative departure from biological and medical studies of CP, and highlight the importance of applying quantitative analytical and spectroscopic methods to a problem central to human health and disease. Taken together, the results will provide new molecular insights into how CP contributes to innate immunity and metal homeostasis. Moreover, the ability to acquire metal ions is an important facet of microbial pathogenesis, and both intercepting microbial metal acquisition and boosting the metal-withholding response of the host present opportunities for antibiotic development. We anticipate that the results from our work will, in the long term, help to guide the development of new antimicrobial therapeutics that target these processes central to the host- pathogen interaction.

Public Health Relevance

Microbial pathogens are among the leading causes of morbidity in the United States, and infections caused by these organisms range from foodborne diarrheal disease to sepsis. The human innate immune system deploys host-defense proteins to inhibit the growth of invading pathogens, and fundamental understanding of these factors is necessary for deciphering the molecular basis of innate immunity and microbial pathogenesis. This work is relevant to the public health issue of infectious disease, and antibiotic development, because knowledge of these processes at the molecular level can guide new approaches to prevent and treat microbial infection in humans.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM118695-03
Application #
9752605
Study Section
Macromolecular Structure and Function A Study Section (MSFA)
Program Officer
Anderson, Vernon
Project Start
2017-08-15
Project End
2021-07-31
Budget Start
2019-08-01
Budget End
2020-07-31
Support Year
3
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Massachusetts Institute of Technology
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
001425594
City
Cambridge
State
MA
Country
United States
Zip Code
02142
Zygiel, Emily M; Nolan, Elizabeth M (2018) Transition Metal Sequestration by the Host-Defense Protein Calprotectin. Annu Rev Biochem 87:621-643
Nakashige, Toshiki G; Bowman, Sarah E J; Zygiel, Emily M et al. (2018) Biophysical Examination of the Calcium-Modulated Nickel-Binding Properties of Human Calprotectin Reveals Conformational Change in the EF-Hand Domains and His3Asp Site. Biochemistry 57:4155-4164
Cunden, Lisa S; Nolan, Elizabeth M (2018) Bioinorganic Explorations of Zn(II) Sequestration by Human S100 Host-Defense Proteins. Biochemistry 57:1673-1680
Hadley, Rose C; Gu, Yu; Nolan, Elizabeth M (2018) Initial Biochemical and Functional Evaluation of Murine Calprotectin Reveals Ca(II)-Dependence and Its Ability to Chelate Multiple Nutrient Transition Metal Ions. Biochemistry 57:2846-2856
Hadley, Rose C; Gagnon, Derek M; Brophy, Megan Brunjes et al. (2018) Biochemical and Spectroscopic Observation of Mn(II) Sequestration from Bacterial Mn(II) Transport Machinery by Calprotectin. J Am Chem Soc 140:110-113