Abstract
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.
Highlights
The septate junctions (SJ) are the cell adhesion structures accounting for the maintenance of selective paracellular barriers in invertebrate tissues [1]
To its vertebrate homologues, this claudin is endocytosed at the SJ level in epidermal cells, suggesting that these adhesion structures include dynamically regulated components that could contribute to junctional plasticity during epithelial morphogenesis
Bou activity is necessary for the formation of septa, as it has been previously reported in many mutants exhibiting defects in SJ organisation and paracellular barrier integrity [6,10,24]
Summary
The septate junctions (SJ) are the cell adhesion structures accounting for the maintenance of selective paracellular barriers in invertebrate tissues [1] They play an analogous role to that of vertebrate tight junctions, as both prevent the unrestricted diffusion of macromolecules, ions and solutes through epithelial layers and are essential for the physiological compartmentalisation of internal organs [2]. Despite their different structural organisations, these two types of occluding junctions display significant parallelisms at the molecular level, as they are known to include different homologous components [3]. These include different membrane proteins, like the claudins Megatrachea (Mega), Kune-kune (Kune) and Sinuous (Sinu) [6,7,8], the adhesion
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