PT  - JOURNAL ARTICLE
AU  - Renata Zuber
AU  - Michaela Norum
AU  - Yiwen Wang
AU  - Kathrin Oehl
AU  - Davide Accardi
AU  - Slawomir Bartozsewski
AU  - Nicole Gehring
AU  - Jürgen Berger
AU  - Matthias Flötenmeyer
AU  - Bernard Moussian
TI  - The ABC transporter Snu drives formation of the lipid-based inward and outward barrier in the skin of <em>Drosophila</em>
AID  - 10.1101/169466
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 169466
4099  - http://biorxiv.org/content/early/2017/07/27/169466.short
4100  - http://biorxiv.org/content/early/2017/07/27/169466.full
AB  - Lipids in extracellular matrices (ECM) contribute to barrier function and stability of epithelial tissues such as the pulmonary alveoli and the skin. In insects, skin waterproofness depends on the outermost layer of the extracellular cuticle termed envelope that contains cuticulin, an unidentified water-repellent complex molecule composed of proteins, lipids and catecholamines. Based on live-imaging analyses of fruit fly larvae, we find that initially envelope units are assembled within vesicles harbouring the ABC transporter Snu and the extracellular protein Snsl. In a second step, the content of these vesicles is distributed to cuticular lipid-transporting nanotubes named pore canals and to the cuticle surface in dependence of Snu function. Consistently, the surface of snu and snsl mutant larvae is depleted from lipids and cuticulin. By consequence, these animals suffer uncontrolled water loss and penetration of xenobiotics. Our data allude to a two-step model of envelope i.e. barrier formation. The proposed mechanism in principle parallels the events occurring during differentiation of the lipid-based ECM by keratinocytes in the vertebrate skin suggesting establishment of analogous mechanisms of skin barrier formation in vertebrates and invertebrates.