Tight junction assembly in human adenocarcinoma cell line: relations to cytoskeletal elements

Abstract

Human colon adenocarcinoma cell line HT29 was found to be a favorable system for the study of junctions assembly. Using scanning electron microscopy (SEM), thin sectioning (TEM) and freeze fracturing, we were able to demonstrate that HT29 cells grown to confluency have desmosomes but clearly lack tight or gap junctions. When treated with trypsin, cells were rounded up, made contacts, and within 15 min formed tight and gap junctions. The desmosomes, however, were split to hemi-desmosomes. These findings agree with results obtained for other experimental systems.In this work we have used cytochalasin B (CB), colchicine (C) and CB + C, drugs known to interfere with microfilaments and microtubules, in order to determine to what extent these structures are involved with the assembly of tight junctions in HT29 cells treated with trypsin. The drugs were added to confluent monolayered cells (CB:20 μg/ml - 1 h; C: 10-4 M - 3 h; CB:20 μg/ml + C: 10-4 M/ml - 3 h), then trypsin was added to a final concentration of 0. 25% for 15 min.