Assembly and sealing of tight junctions: Possible participation of G-proteins,phospholipase C,protein kinase C and calmodulin |
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Authors: | M S Balda L González-Mariscal R G Contreras M Macias-Silva M E Torres-Marquez J A García Sáinz M Cereijido |
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Institution: | (1) Department of Physiology and Biophysics, Center for Research and Advanced Studies, 07000 Mexico 14, D.F., Mexico;(2) Instituto de Fisiologia Celular, UNAM, 04510 Mexico, D.F., Mexico |
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Abstract: | Summary The making and sealing of a tight junction (TJ) requires cell-cell contacts and Ca2–, and can be gauged through the development of transepithelial electrical resistance (TER) and the accumulation of ZO-1 peptide at the cell borders. We observe that pertussis toxin increases TER, while AIF3 and carbamil choline (carbachol) inhibit it, and 5-guanylylimidodiphosphate (GTPs) blocks the development of a cell border pattern of ZO-1, suggesting that G-proteins are involved. Phospholipase C (PLC) and protein kinase C (PKC) probably participate in these processes since (i) activation of PLC by thyrotropin-1 releasing hormone increases TER, and its inhibition by neomycin blocks the development of this resistance; (ii) 1,2-dioctanoylglycerol, an activator of PKC, stimulates TER development, while polymyxin B and 1-(5-isoquinoline sulfonyl)-2-methyl-piperazine dihydrochloride (H7), which inhibit this enzyme, abolish TER. Addition of 3-isobutyl-1-methyl-xanthine, dB-cAMP or forskolin do not enhance the value of TER, but have just the opposite effect. Trifluoperazine and calmidazoline inhibit TER development, suggesting that calmodulin (CaM) also plays a role in junction formation. These results indicate that junction formation may be controlled by a network of reactions where G-proteins, phospholipase C, adenylate cyclase, protein kinase C and CaM are involved. |
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Keywords: | epithelia tight junctions G-protein Ca2+-MDCK phospholipase C protein kinase C calmodulin exocytic fusion |
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