Graham P L, Johnson J J, Wang S, Sibley M H, Gupta M C, Kramer J M
Northwestern University Medical School, Department of Cell and Molecular Biology, Chicago, Illinois 60611, USA.
J Cell Biol. 1997 Jun 2;137(5):1171-83. doi: 10.1083/jcb.137.5.1171.
Type IV collagen in Caenorhabditis elegans is produced by two essential genes, emb-9 and let-2, which encode alpha1- and alpha2-like chains, respectively. The distribution of EMB-9 and LET-2 chains has been characterized using chain-specific antisera. The chains colocalize, suggesting that they may function in a single heterotrimeric collagen molecule. Type IV collagen is detected in all basement membranes except those on the pseudocoelomic face of body wall muscle and on the regions of the hypodermis between body wall muscle quadrants, indicating that there are major structural differences between some basement membranes in C. elegans. Using lacZ/green fluorescent protein (GFP) reporter constructs, both type IV collagen genes were shown to be expressed in the same cells, primarily body wall muscles, and some somatic cells of the gonad. Although the pharynx and intestine are covered with basement membranes that contain type IV collagen, these tissues do not express either type IV collagen gene. Using an epitope-tagged emb-9 construct, we show that type IV collagen made in body wall muscle cells can assemble into the pharyngeal, intestinal, and gonadal basement membranes. Additionally, we show that expression of functional type IV collagen only in body wall muscle cells is sufficient for C. elegans to complete development and be partially fertile. Since type IV collagen secreted from muscle cells only assembles into some of the basement membranes that it has access to, there must be a mechanism regulating its assembly. We propose that interaction with a cell surface-associated molecule(s) is required to facilitate type IV collagen assembly.
秀丽隐杆线虫中的IV型胶原蛋白由两个必需基因emb-9和let-2产生，这两个基因分别编码α1样链和α2样链。使用链特异性抗血清对EMB-9和LET-2链的分布进行了表征。这些链共定位，表明它们可能在单个异源三聚体胶原蛋白分子中发挥作用。在除体壁肌肉假体腔面和体壁肌肉象限之间的皮下区域之外的所有基底膜中都检测到了IV型胶原蛋白，这表明秀丽隐杆线虫的一些基底膜之间存在主要的结构差异。使用lacZ/绿色荧光蛋白（GFP）报告构建体，发现两个IV型胶原蛋白基因都在相同的细胞中表达，主要是体壁肌肉和性腺的一些体细胞。尽管咽部和肠道覆盖着含有IV型胶原蛋白的基底膜，但这些组织不表达任何一个IV型胶原蛋白基因。使用一个带有表位标签的emb-9构建体，我们表明体壁肌肉细胞中产生的IV型胶原蛋白可以组装到咽部、肠道和性腺的基底膜中。此外，我们表明仅在体壁肌肉细胞中表达功能性IV型胶原蛋白就足以使秀丽隐杆线虫完成发育并部分生育。由于从肌肉细胞分泌的IV型胶原蛋白仅组装到它能够接触到的一些基底膜中，所以必定存在一种调节其组装的机制。我们提出需要与细胞表面相关分子相互作用以促进IV型胶原蛋白的组装。
