Connexin 43 (Cx43) is a predominant gap junction (GJ) protein that is expressed by pulmonary alveolar epithelial cells, both in situ and in primary culture. Cx43 expression increases with culture time, as type II cell isolates assume a more type I cell-like phenotype. In these cell populations, Cx trafficking, assembly, and turnover are regulated by diverse pathways, including those that involve integrin-mediated cell-extracellular matrix interactions and/or elements of the cytoskeleton. Immunocytochemical double labeling demonstrates the association of microtubules with the cellular internalization of Cx43-positive GJ plaques. Antibodies against the α5 integrin subunit block cell-extracellular matrix interactions, with little effect on tubulin expression. In contrast, the inhibition of mitogen-activated protein kinase kinase by PD98059 reduces tubulin expression, based either on direct immunostaining or on Western blot analysis. To examine the association of microtubules with GJ plaques, day 3 cells were exposed with colchicine (0.5 to 24 h). The drug disassembled the microtubules within 60 min, whereas Western blot showed no change in tubulin abundance. Colchicine caused a parallel redistribution of immunopositive Cx43 from the plasma membrane to the cytosol. These data are consistent with the conclusion that in alveolar epithelial cells, the direct association of cytoskeletal proteins with GJs plays a role in the regulation of Cx43 expression and intracellular distribution via integrin-mediated signal transduction pathways.