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Zofia Zielicka, Jennifer A E Williams, Stephen E Moss; Gap junctions modulate the phagocytic activity of retinal pigment epithelial cells. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2322.
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© ARVO (1962-2015); The Authors (2016-present)
The retinal pigment epithelium (RPE) is composed of highly polarised cells with complex cell biology, which reflects their multiple functions in mammalian vision. Expression of gap junction proteins in the RPE, specifically connexin 43 (Cx43), is known to be critical in ocular development. However, the role of gap junctions in terminally differentiated mammalian RPE has yet to be established. Our aim was to investigate a potential role for intercellular gap junction communication during photoreceptor outer segment (POS) phagocytosis.
Immunofluorescence studies of mammalian RPE cells were used to establish the localisation of Cx43 gap junctions, and to examine the effects of a gap junction inhibitor, 18-β glycyrrhetinic acid (18-β GA). Phagocytosis assays were performed on 18-β GA-treated cells to investigate the effects of gap junction disruption on POS binding and internalisation. To investigate the effects of gap junction disruption on intracellular signalling, western blots were performed to examine various phosphorylated proteins, in particular phosphorylated Cx43.
Cx43 is expressed in mammalian RPE cells, but in the presence of 18-β GA gap junction disassembly occurs. Gap junction disruption was associated with a significant reduction in POS binding to RPE cells during phagocytosis (P < 0.05), but with no effect on POS internalisation. Western blot analysis revealed that phosphorylation of Cx43 on serine 368 occurred in the presence of 18-β GA treatment, and during phagocytosis of POS.
18-β GA mediated RPE gap junction disruption is characterised by a reduction in Cx43 assembly associated with phosphorylation on serine 368, and POS binding to RPE during phagocytosis requires functionally intact Cx43 gap junctions.
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