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R. E. Hausman, U. Salimi, E. Thurber; Possible Role for Integrins in Embryonic Chick Retina Cell to Cell Adhesion. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1231.
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Embryonic retina development requires changing cell-cell and cell-matrix interactions. These changes in adhesion require modifications in the conformation of cell surface receptors. We have shown that some rearrangements require disulfide bond reshuffling mediated by the cell surface protein disulfide isomerase, retina cognin. Our previous work suggested a role for receptors of the size and ion sensitivity of integrins. Here we ask whether integrins normally thought of as cell-matrix adhesion receptors, also function in cell-cell adhesion, and if they are substrates for this disulfide exchange. Using a simple retina cell reaggregation assay, we asked if a ligand to some integrins, the tripeptide RGD, or function-blocking antibodies to the beta1 integrin subunit (CSAT & JG22) interfered with retina cell-cell interactions.
Embryonic day 7-10 chicken retina were dissected and separated into suspensions of single cells using a standard trypsin or trypsin-free procedure. Some cell suspensions were exposed to either the peptide or antibodies with or without the cognin function blocking agent DTNB [5,5'-dithio-bis (2-nitro-benzoic acid)]. Control and experimentally-treated cell suspensions were allowed to reaggregate for 1 hour during which either the cells not in aggregates or the increase in aggregates were counted. Early embryonic chick cells from many tissues rapidly reaggregate in simple balanced salt solution.
As we have shown previously, while the untreated retina cells rapidly reaggregate this reaggregation is partially blocked by DTNB. Cells exposed to the non-binding RGE peptide aggregate normally but those exposed to RGD aggregate only to the same extent as those in DTNB. Cells exposed to both RGD and DTNB exhibit less aggregation than in either agent alone. Cells pre-treated with the either the CSAT or JG22 antisera aggregate only to the level seen in DTNB but, in contrast, the addition of DTNB yields no further reduction in aggregation.
The results suggest that integrin or integrin-like mechanisms play a role in cell-cell adhesion in this highly simplified assay system. The mechanisms involved are sensitive to the integrin ligand, RGD, and partially dependent on a molecule which binds the CSAT and JG22 antibodies (to the beta1 integrin subunit). Since other RGD-binding integrins containing the beta3 subunit are on retinal cells there may be two different cell-cell adhesion complexes involving integrins, one of which requires rearrangement of disulfide bonds for activity.
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