Department of Cell & Developmental Biology, University of Pennsylvania School of Medicine, 421 Curie Boulevard, 1214 BRB II/III, Philadelphia, Pennsylvania 19104, USA.
Nat Cell Biol. 2012 Mar 11;14(4):386-93. doi: 10.1038/ncb2454.
Seamless tubes form intracellularly without cell-cell or autocellular junctions. Such tubes have been described across phyla, but remain mysterious despite their simple architecture. In Drosophila, seamless tubes are found within tracheal terminal cells, which have dozens of branched protrusions extending hundreds of micrometres. We find that mutations in multiple components of the dynein motor complex block seamless tube growth, raising the possibility that the lumenal membrane forms through minus-end-directed transport of apical membrane components along microtubules. Growth of seamless tubes is polarized along the proximodistal axis by Rab35 and its apical membrane-localized GAP, Whacked. Strikingly, loss of whacked (or constitutive activation of Rab35) leads to tube overgrowth at terminal cell branch tips, whereas overexpression of Whacked (or dominant-negative Rab35) causes formation of ectopic tubes surrounding the terminal cell nucleus. Thus, vesicle trafficking has key roles in making and shaping seamless tubes.
细胞内形成无细胞-细胞或自体细胞连接的无缝管。这种管已经在各个门中被描述过，但尽管它们的结构简单，仍然很神秘。在果蝇中，无缝管存在于气管末端细胞中，这些细胞有数十个分支突起延伸数百微米。我们发现动力蛋白复合物的多个成分的突变阻止了无缝管的生长，这增加了这样一种可能性，即通过沿着微管向微管负端运输顶端膜成分形成腔膜。无缝管的生长沿着近端-远端轴由 Rab35 和其顶端膜定位的 GAP Whacked 极化。引人注目的是，缺失 whacked（或 Rab35 的组成型激活）导致末端细胞分支尖端的管过度生长，而 Whacked 的过表达（或显性负性 Rab35）导致围绕末端细胞核形成异位管。因此，囊泡运输在形成和塑造无缝管方面起着关键作用。
