Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, 35043 Marburg, Germany.
J Cell Sci. 2011 Oct 1;124(Pt 19):3266-78. doi: 10.1242/jcs.083907. Epub 2011 Sep 6.
In the Drosophila embryo, transient cell adhesion during myoblast fusion is known to lead to the formation of fusion-restricted myogenic-adhesive structures (FuRMASs). Here, we report that within these FuRMASs, a Drosophila homologue of human and mouse swiprosins (EF-hand-domain-containing proteins) is expressed, which we named Drosophila Swiprosin-1 (Drosophila Swip-1). Drosophila Swip-1 is highly conserved and is closely related to the calcium-binding proteins swiprosin-1 and swiprosin-2 that have a role in the immune system in humans and mice. Our study shows that Drosophila Swip-1 is also expressed in corresponding cells of the Drosophila immune system. During myoblast fusion, Drosophila Swip-1 accumulates transiently in the foci of fusion-competent myoblasts (FCMs). Both the EF-hand and the coiled-coil domain of Drosophila Swip-1 are required to localise the protein to these foci. The formation of Drosophila Swip-1 foci requires successful cell adhesion between FCMs and founder cells (FCs) or growing myotubes. Moreover, Drosophila Swip-1 foci were found to increase in number in sing(22) mutants, which arrest myoblast fusion after prefusion complex formation. By contrast, Drosophila Swip-1 foci are not significantly enriched in blow(2) and kette(J4-48) mutants, which stop myogenesis beyond the prefusion complex stage but before plasma membrane merging. Therefore, we hypothesise that Drosophila Swip-1 participates in the breakdown of the prefusion complex during the progression of myoblast fusion.
在果蝇胚胎中，已知短暂的细胞黏附在成肌细胞融合期间会导致融合受限的肌源性黏附结构（FuRMASs）的形成。在这里，我们报告在这些 FuRMASs 中，果蝇与人和鼠的 swiprosin 同源物（含 EF 手结构域的蛋白质）表达，我们将其命名为果蝇 Swiprosin-1（Drosophila Swip-1）。果蝇 Swip-1 高度保守，与钙结合蛋白 swiprosin-1 和 swiprosin-2 密切相关，后者在人类和鼠的免疫系统中发挥作用。我们的研究表明，果蝇 Swip-1 也在果蝇免疫系统的相应细胞中表达。在成肌细胞融合期间，果蝇 Swip-1 短暂地在融合能力成肌细胞（FCMs）的焦点中积累。果蝇 Swip-1 的 EF 手和卷曲螺旋结构域都需要将该蛋白定位到这些焦点。果蝇 Swip-1 焦点的形成需要 FCMs 和创始细胞（FCs）或生长的肌管之间成功的细胞黏附。此外，在 sing(22) 突变体中发现果蝇 Swip-1 焦点的数量增加，sing(22) 突变体在融合前复合物形成后阻止成肌细胞融合。相比之下，果蝇 Swip-1 焦点在 blow(2) 和 kette(J4-48) 突变体中没有显著富集，blow(2) 和 kette(J4-48) 突变体在融合前复合物阶段之后但在质膜融合之前停止肌发生。因此，我们假设果蝇 Swip-1 参与成肌细胞融合过程中融合前复合物的解体。
