Expression, localization, and function of junctional adhesion molecule-C (JAM-C) in human retinal pigment epithelium.
OBJECTIVE
To determine the localization of JAM-C in human RPE and characterize its functions.


METHODS
Immunofluorescence, Western blot, and PCR was used to identify the localization and expression of JAM-C, ZO-1, N-cadherin, and ezrin in cultures of human fetal RPE (hfRPE) with or without si-RNA mediated JAM-C knockdown and in adult native RPE wholemounts. A transepithelial migration assay was used to study the migration of leukocytes through the hfRPE monolayer.


RESULTS
JAM-C localized at the tight junctions of cultured hfRPE cells and adult native RPE. During initial junction formation JAM-C was recruited to the primordial cell-cell contacts and after JAM-C knockdown, the organization of N-cadherin and ZO-1 at those contacts was disrupted. JAM-C knockdown caused a delay in the hfRPE cell polarization, as shown by reduced apical staining of ezrin. JAM-C inhibition significantly decreased the chemokine-induced transmigration of granulocytes but not monocytes through the hfRPE monolayer.


CONCLUSIONS
JAM-C localizes specifically in the tight junctions of hfRPE and adult native RPE. It is important for tight junction formation in hfRPE, possibly by regulating the recruitment of N-cadherin and ZO-1 at the cell-cell contacts, and has a role in the polarization of hfRPE cells. Finally, JAM-C promotes the basal-to-apical transmigration of granulocytes but not monocytes through the hfRPE monolayer.
Economopoulou
Matina
M
Section for Epithelial and Retinal Physiology and Disease, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892-2510, USA.
Hammer
Jeffrey
J
Wang
Fei
F
Fariss
Robert
R
Maminishkis
Arvydas
A
Miller
Sheldon S
SS
D015703:Antigens, CD / Q000378:metabolism; D015153:Blotting, Western; D015820:Cadherins / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D054441:Cell Migration Assays, Leukocyte; D016764:Cell Polarity; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology; D003598:Cytoskeletal Proteins / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D006098:Granulocytes / Q000502:physiology; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D009000:Monocytes / Q000502:physiology; D010750:Phosphoproteins / Q000378:metabolism; D016133:Polymerase Chain Reaction; D034741:RNA, Small Interfering / Q000494:pharmacology; D055213:Retinal Pigment Epithelium / Q000196:embryology / Q000378:metabolism*; D019108:Tight Junctions / Q000378:metabolism; D062826:Zonula Occludens-1 Protein; D000099149:Ezrin
D015703:Antigens, CD; D015820:Cadherins; D015815:Cell Adhesion Molecules; D016207:Cytokines; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D010750:Phosphoproteins; D034741:RNA, Small Interfering; D062826:Zonula Occludens-1 Protein; D000099149:Ezrin; C050361:CDH2 protein, human; C448000:JAM3 protein, human; C569042:TJP1 protein, human