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Jeff Romano, Robert L McKown, Regis P Kowalski, Tadayuki Iwase, Gordon W Laurie; Release of Lacritin’s C-Terminal Bactericidal Domain by Esp, a Serine Protease Highly Expressed in Coagulase Negative Clinical Isolates from Bacterial Keratitis, but not from Endophthalmitis or Blepharitis. Invest. Ophthalmol. Vis. Sci. 2016;57(12):6190.
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© ARVO (1962-2015); The Authors (2016-present)
Lacritin is a multifunctional tear protein with latent bactericidal activity. Its C-terminal bactericidal fragment is constitutively released into tears, likely by a serine protease. Released fragment (alone or in synergy with others) underlies the sterility of human tears (McKown et al, JBC ’14). Here we asked whether commensal S. epidermidis may contribute to lacritin C-terminal proteolysis via its serine protease Esp that was previously shown to disrupt S. aureus biofilm in nasal colonization (Iwase et al, Nature, ‘10).
Recombinant lacritin alone, or mixtures of recombinant lacritin, recombinant Esp and thermolysin, or recombinant lacritin and thermolysin were incubated for 20 hours at 37°C, separated by SDS-PAGE and blotted for lacritin. Eight coagulase negative clinical isolates each from bacterial keratitis, blepharitis and endophthalmitis were expanded, supernatants collected, pooled, separated by SDS-PAGE, and then blotted for Esp. All keratitis supernatants were also individually blotted for Esp. Recombinant Esp without incubation served as an internal blotting control.
Esp, but not Esp activating enzyme thermolysin, releases a <10 kDa band characteristic of the C-terminal bactericidal fragment. Lacritin alone incubated in parallel remained intact. Clinical isolate blotting detected Esp only in bacterial keratitis, and when examined separately in most keratitis isolates.
Release of lacritin’s C-terminal bactericidal fragment appears to be in part under the control of commensal S. epidermidis via the release of serine protease Esp that releases this latent activity into tears.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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