Increasing paracellular porosity by E-cadherin peptides: discovery of bulge and groove regions in the EC1-domain of E-cadherin.

PURPOSE: The objective of this work is to evaluate the ability of peptides derived from the bulge (HAV-peptides) and groove (ADT-peptides) regions of E-cadherin EC1-domain to increase the paracellular porosity of the intercellular junctions of Madin-Darby canine kidney (MDCK) cell monolayers.
METHODS: Peptides were synthesized using a solid-phase method and were purified using semi-preparative HPLC. MDCK monolayers were used to evaluate the ability of cadherin peptides to modulate cadherin-cadherin interactions in the intercellular junctions. The increase in intercellular junction porosity was determined by the change in transepithelial electrical resistance (TEER) values and the paracellular transport of 14C-mannitol.
RESULTS: HAV- and ADT-peptides can lower the TEER value of MDCK cell monolayers and enhance the paracellular permeation of 14C-mannitol. HAV- and ADT-decapeptides can modulate the intercellular junctions when they are added from the basolateral side but not from the apical side; on the other hand. HAV- and ADT-hexapeptides increase the paracellular porosity of the monolayers when added from either side. Conjugation of HAV- and ADT-peptides using omega-aminocaproic acid can only work to modulate the paracellular porosity when ADT-peptide is at the N-terminus and HAV-peptide is at the C-terminus; because of its size, the conjugate can only modulate the intercellular junction when added from the basolateral side.
CONCLUSIONS: Peptides from the bulge and groove regions of the EC1 domain of E-cadherin can inhibit cadherin-cadherin interactions, resulting in the opening of the paracellular junctions. These peptides may be used to improve paracellular permeation of peptides and proteins. Furthermore, this work suggests that both groove and bulge regions of EC-domain are important for cadherin-cadherin interactions.