[log in to unmask]" type="cite">Thesis
Defense Announcement
To: The George Mason University Community
Candidate: Nicholas Leverone
Program: Master of Science in Biology
Date: Tuesday April 9, 2013
Time: 9:30 a.m.
Place: George Mason University,
Prince William Campus
Discovery Hall, Room 153
Title: "Small Peptide Derived from Human MMP12 CTD Is Antibacterial against Gram-negative and Gram-positive Pathogens,
Including Multi-drug Resistant S. aureus (MRSA)"
Thesis
Director:
Dr. Monique van Hoek
Thesis
Committee: Dr. Serguei Popov, Dr. Barney Bishop
A
copy of the thesis will be available in the Johnson Center Library. All are invited to attend the defense.
ABSTRACT
Matrix Metalloproteinase 12 (MMP12) is a macrophage
produced proteolytic enzyme also known as macrophage elastase. The
proteinase activity is located at its N-terminal. The C-terminal of the
protein is cleaved during processing, releasing the Hemopexin-like
Carboxy-terminal domain (CTD) [1-3]. The biological function of the CTD
is not known. Previous work by our group demonstrated that murine MMP12
had bactericidal activity in a small peptide contained within the
middle third of the CTD [4]. The goal of this study was to examine
human MMP12 to determine if similar CTD-antibacterial activity could be
identified. We investigated the antimicrobial properties of human MMP12
CTD with the goal of identifying potential antimicrobial peptides
within this hemopexin-like protein. We tested the full-length human CTD
domain for antimicrobial activity against S. aureus and other bacteria.
We used three-dimensional structure analysis, comparison of known human
peptides identified in blood, and bioinformatic analysis of sequences
using peptide databases in order to identify strong candidates for
antimicrobial activity. These candidate peptides were then synthesized
and tested for antimicrobial peptide activity against S. aureus. Active
peptides from this screen were further tested against other organisms,
for biofilm inhibition, and for their effect on bacterial membrane
integrity. The human CTD of MMP12 is antibacterial against S. aureus,
P. aeruginosa, E. coli, and A. baumannii. We tested small peptides
derived from CTD for antibacterial activity. Five active peptides were
identified. One peptide, KY-27, displayed the lowest half-maximal
effective concentration (EC50), 27.8 µM against S. aureus, and 47.45 µM
against MRSA. This peptide was antimicrobial against both Gram-positive
and Gram-negative bacteria, but did not inhibit biofilm formation by
these organisms. When tested in an in vivo model, this peptide was able
to increase survival in G. mellonella when challenged with P.
aeruginosa. Our studies demonstrate that the human MMP12 CTD is
antibacterial against S. aureus. We also identified a small 27 AA
peptide of the CTD, KY-27, which has strong antimicrobial activity
against S. aureus and multiple other pathogenic bacteria. These results
suggest that KY-27 may be a vital component of the CTD bactericidal
effects.
###