Expression of JAM-A in the human corneal endothelium and retinal pigment epithelium: localization and evidence for role in barrier function.
OBJECTIVE
Junctional adhesion molecules (JAMs) are a family of adhesion proteins found in intercellular junctions. Evidence suggests that JAM-A is important for the regulation of tight junction assembly and epithelial barrier function. The authors recently reported that JAM-A is expressed in rabbit corneal endothelium and that antibody to JAM-A produces corneal swelling. In the present study, they investigate JAM-A expression in the human corneal endothelium and retinal pigment epithelium (RPE) and examine the effect of a function-blocking antibody to JAM-A on the permeability of cultured RPE cell monolayers.


METHODS
Expression of JAM-A in human corneal endothelium, human RPE tissue, and cultured ARPE-19 monolayers was assessed by immunofluorescence confocal microscopy. Localization of JAM-A was compared with the tight junction-associated protein zonula occludens-1 (ZO-1). To investigate JAM-A function in ARPE-19 cells, ARPE-19 monolayers were subjected to a calcium switch protocol to disrupt cell junctions and treated with a function-blocking antibody to JAM-A or an isotype-matched control. Dextran flux assays were performed to assess the effect of JAM-A antibody on ARPE-19 monolayer permeability.


RESULTS
Expression of JAM-A was observed in human corneal endothelium, and its distribution correlated with the tight junction-associated protein ZO-1. In addition, expression of JAM-A was observed in human RPE and in intercellular junctions of ARPE-19 monolayers. The localization pattern of JAM-A in the RPE and ARPE-19 monolayers was similar to that of ZO-1. ARPE-19 monolayers treated with antibody to JAM-A demonstrated a 33% increase in permeability to 10,000 MWt dextran compared with monolayers treated with control antibody.


CONCLUSIONS
Results of this study provide new information about JAM-A expression in tight junctions of the human corneal endothelium and human RPE. The observation that antibodies to JAM-A increase ARPE-19 monolayer permeability is consistent with previous findings of JAM-A function in epithelial tight junctions and suggests JAM-A may have a role in the regulation of RPE barrier function.
Mandell
Kenneth J
KJ
Epithelial Pathobiology Research Unit, Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA. kjmande@emory.edu
Berglin
Lennart
L
Severson
Eric A
EA
Edelhauser
Henry F
HF
Parkos
Charles A
CA
D001692:Biological Transport; D015153:Blotting, Western; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002478:Cells, Cultured; D003911:Dextrans / Q000378:metabolism; D004728:Endothelium, Corneal / Q000378:metabolism*; D006801:Humans; D007136:Immunoglobulins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D010539:Permeability; D010750:Phosphoproteins / Q000378:metabolism; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D011956:Receptors, Cell Surface; D019108:Tight Junctions / Q000378:metabolism*; D062826:Zonula Occludens-1 Protein
D015815:Cell Adhesion Molecules; D003911:Dextrans; C407243:F11R protein, human; D007136:Immunoglobulins; D008565:Membrane Proteins; D010750:Phosphoproteins; D011956:Receptors, Cell Surface; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein