Abstract
Purpose :
CUB domain-containing protein 1 (CDCP1) was originally discovered to be overexpressed on certain solid tumor cells, regulating tumor-cell anoikis resistance. We recently identified CDCP1 as a ligand of CD6, which is a marker of T cells, suggesting that CDCP1 could regulate immune responses. Nevertheless, the distribution of CDCP1 in the eye and its potential role in ocular homeostasis have not been studied.
Methods :
Distribution of CDCP1 in the eye was first examined by immunofluorescent staining of ocular sections from C57BL/6 wild-type (WT) and CDCP1 knockout (KO) mice followed by confocal microscopic analysis. Expression of CDCP1 was validated by flow cytometric analysis of respective mouse and human ocular cells. To determine whether CDCP1 has a role in the development of bacterial keratitis, corneas of anesthetized WT and CDCP1 KO mice were scratched and allowed to heal for 4 hr (partially heal) before inoculation of 1x105 CFU (in 5 ml saline) Pseudomonas aeruginosa clinical isolate (invasive strain). Disease severity was monitored for 3 days and scored daily (0-16 points). At the time of sacrifice, enucleated eyes were homogenized in 1 ml PBS to quantitate viable bacterial load.
Results :
Confocal micrographs showed strong membrane staining of CDCP1 in the corneal epithelium of WT but not CDCP1 KO mice. This observation was confirmed by flow cytometric analyses using respective mouse primary corneal epithelial cells as well as an immortalized human corneal epithelial cell line. CDCP1 KO mice developed significantly exacerbated keratitis compared with WT mice (day 3 post-inoculation disease scores of 11.6±1.1 vs 7.5±1.4; p<0.0001, t-test). In addition, the bacterial burden was much higher in infected eyes from CDCP1 KO mice than in WT mice (8.3±1.2x10^4 vs. 3.6±0.62x10^4 CFU; P<0.005, t-test).
Conclusions :
CDCP1 is highly and selectively expressed on corneal epithelial cells. CDCP1 has a previously unknown, but pivotal role in the development of P. aeruginosa keratitis. These results suggest that CDCP1 could be a new therapeutic target for treating this potentially blinding disease.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.