Boudin trafficking reveals the dynamic internalisation of specific septate junction components in Drosophila

The maintenance of paracellular barriers in invertebrate epithelia depends on the integrity of specific cell adhesion structures known as septate junctions (SJ). Multiple studies in Drosophila have revealed that these junctions have a stereotyped architecture resulting from the association in the lateral membrane of a large number of components. However, little is known about the dynamic organisation adopted by these multi-protein complexes in living tissues. We have used live imaging techniques to show that the Ly6 protein Boudin is a component of these adhesion junctions and can diffuse systemically to associate with the SJ of distant cells. We also observe that this protein and the claudin Kune-kune are endocytosed in epidermal cells during embryogenesis. Our data reveal that the SJ contain a set of components exhibiting a high membrane turnover, a feature that could contribute in a tissue-specific manner to the morphogenetic plasticity of these adhesion structures.