Institute of Zoology, Developmental Biology Unit, University of Cologne, Cologne, Germany.
Center for Biochemistry, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany; Department of Pediatrics and Adolescent Medicine, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany.
Matrix Biol. 2022 Sep;112:132-154. doi: 10.1016/j.matbio.2022.08.009. Epub 2022 Aug 22.
Hemicentins are large proteins of the extracellular matrix that belong to the fibulin family and play pivotal roles during development and homeostasis of a variety of invertebrate and vertebrate tissues. However, bona fide interaction partners of hemicentins have not been described as yet. Here, applying surface plasmon resonance spectroscopy and co-immunoprecipitation, we identify the basement membrane protein nidogen-2 (NID2) as a binding partner of mouse and zebrafish hemicentin-1 (HMCN1), in line with the formerly described essential role of mouse HMCN1 in basement membrane integrity. We show that HMCN1 binds to the same protein domain of NID2 (G2) as formerly shown for laminins, but with an approximately 3.5-fold lower affinity and in a competitive manner. Furthermore, immunofluorescence and immunogold labeling revealed that HMCN1/Hmcn1 is localized close to basement membranes and in partial overlap with NID2/Nid2a in different tissues of mouse and zebrafish. Genetic knockout and antisense-mediated knockdown studies in zebrafish further show that loss of Nid2a leads to similar defects in fin fold morphogenesis as the loss of Laminin-α5 (Lama5) or Hmcn1. Finally, combined partial loss-of-function studies indicated that nid2a genetically interacts with both hmcn1 and lama5. Together, these findings suggest that despite their mutually exclusive physical binding, hemicentins, nidogens, and laminins tightly cooperate and support each other during formation, maintenance, and function of basement membranes to confer tissue linkage.
半钙黏蛋白是细胞外基质中的大型蛋白,属于纤连蛋白家族,在多种无脊椎动物和脊椎动物组织的发育和稳态中发挥关键作用。然而,目前尚未描述半钙黏蛋白的真正相互作用伙伴。在这里,我们应用表面等离子体共振光谱和共免疫沉淀技术,确定了基底膜蛋白巢蛋白-2(NID2)是小鼠和斑马鱼半钙黏蛋白-1(HMCN1)的结合伴侣,这与先前描述的小鼠 HMCN1 在基底膜完整性中的重要作用一致。我们表明,HMCN1 与 NID2(G2)的相同蛋白结构域结合,正如以前在层粘连蛋白中所显示的那样,但亲和力约低 3.5 倍,且呈竞争性。此外,免疫荧光和免疫金标记显示,HMCN1/Hmcn1 在不同组织中靠近基底膜定位,并与 NID2/Nid2a 部分重叠。在斑马鱼中的基因敲除和反义介导的敲低研究进一步表明,Nid2a 的缺失导致鳍褶形态发生的类似缺陷,就像层粘连蛋白-α5(Lama5)或 Hmcn1 的缺失一样。最后,联合部分功能丧失研究表明,nid2a 在遗传上与 hmcn1 和 lama5 相互作用。总之,这些发现表明,尽管它们具有相互排斥的物理结合,但半钙黏蛋白、巢蛋白和层粘连蛋白在基底膜的形成、维持和功能过程中紧密合作并相互支持,以赋予组织连接。
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