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Updated: Aug 9, 2026

Large-Scale Purification of Porcine or Bovine Photoreceptor Outer Segments for Phagocytosis Assays on Retinal Pigment Epithelial Cells
Published on: December 12, 2014
Inhibition of Bacterial Peptidoglycan Cytopathy by Retina Pigment Epithelial PGRP2 Amidase
Marlyn P Langford1, Laura A Perilloux-Lyons2, A Scott Kavanaugh2
1Department of Ophthalmology, Louisiana State University Health Sciences Center, Shreveport, LA, USA. marlyn.langford@lsuhs.edu.
Abstract:
Peptidoglycan (PGN) recognition protein 2 (PGRP2; N-acetylmuramyl-L-alanine amidase (NAMAA)) activity in corneal epithelial cells is thought to inhibit corneal inflammation by reducing the PGN-induced cytokines. PGRP2 has not been reported in human retinal pigment epithelial (RPE) cells. RPE cell lysate NAMAA activity was measured densitometrically via cleavage of FITC-tagged muramyl dipeptide (FITCMDP). RPE lysate degradation of the cytopathic activity of nucleotide-binding oligomerization domain (NOD) receptor agonists was assessed by caspase-3 activation and DNA ladder detection and quantitation. PGRP2/NAMAA protein was detected in RPE cells by immunofluorescent antibody assay. RPE lysate NAMAA cleaved FITCMDP in a dose- and time-dependent manner. RPE lysate selectively inhibited PGN cytopathic activity of NOD1 agonists containing D-γ-glutamyl-meso-diaminopimelic acid and NOD2 containing L-alanyl-D-isoglutamine. The results suggest RPE PGRP2 amidase selectively degrades PGN that stimulate NOD-mediated cytopathic activity. The failure of RPE NAMAA to degrade pro-inflammatory PGN may play a role in bacterial retinopathies.
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