Bernfield M, Sanderson R D
Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115.
Philos Trans R Soc Lond B Biol Sci. 1990 Mar 12;327(1239):171-86. doi: 10.1098/rstb.1990.0052.
Cellular behaviour during development is dictated, in part, by the insoluble extracellular matrix and the soluble growth factor peptides, the major molecules responsible for integrating cells into morphologically and functionally defined groups. These extracellular molecules influence cellular behaviour by binding at the cell surface to specific receptors that transduce intracellular signals in various ways not yet fully clear. Syndecan, a cell surface proteoglycan found predominantly on epithelia in mature tissues binds both extracellular matrix components (fibronectin, collagens I, III, V, and thrombospondin) and basic fibroblast growth factor (bFGF). Syndecan consists of chondroitin sulfate and heparan sulphate chains linked to a 31 kilodalton (kDa) integral membrane protein. Syndecan represents a family of integral membrane proteoglycans that differ in extracellular domains, but share cytoplasmic domains. Syndecan behaves as a matrix receptor: it binds selectively to components of the extracellular matrix, associates intracellularly with the actin cytoskeleton when cross-linked at the cell surface, its extracellular domain is shed upon cell rounding and it localizes solely to basolateral surfaces of simple epithelia. Mammary epithelial cells made syndecan-deficient become fibroblastic in morphology and cell behaviour, showing that syndecan maintains epithelial cell morphology. Syndecan changes in quantity, location and structure during development: it appears initially on four-cell embryos (prior to its known matrix ligands), becomes restricted in the pre-implementation embryo to the cells that will form the embryo proper, changes its expression due to epithelial-mesenchymal interactions (for example, induced in kidney mesenchyme by the ureteric bud), and with association of cells with extracellular matrix (for example, during B-cell differentiation), and ultimately, in mature tissues becomes restricted to epithelial tissues. The number and size of its glycosaminoglycan chains vary with changes in cell shape and organization yielding tissue type-specific polymorphic forms of syndecan. Its interactions with the major extracellular effector molecules that influence cell behaviour, its role in maintaining cell shape and its spatial and temporal changes in expression during development indicate that syndecan is involved in morphogenesis.
发育过程中的细胞行为部分由不溶性细胞外基质和可溶性生长因子肽决定，这些是负责将细胞整合为形态和功能明确的群体的主要分子。这些细胞外分子通过在细胞表面与特定受体结合来影响细胞行为，这些受体以各种尚未完全清楚的方式转导细胞内信号。Syndecan是一种主要存在于成熟组织上皮细胞表面的蛋白聚糖，它既能结合细胞外基质成分（纤连蛋白、I型、III型、V型胶原蛋白和血小板反应蛋白），也能结合碱性成纤维细胞生长因子（bFGF）。Syndecan由硫酸软骨素和硫酸乙酰肝素链连接到一个31千道尔顿（kDa）的整合膜蛋白组成。Syndecan代表了一类整合膜蛋白聚糖家族，它们在细胞外结构域不同，但共享细胞质结构域。Syndecan作为一种基质受体发挥作用：它选择性地结合细胞外基质成分，当在细胞表面交联时在细胞内与肌动蛋白细胞骨架结合，其细胞外结构域在细胞变圆时脱落，并且仅定位于单层上皮的基底外侧表面。缺乏Syndecan的乳腺上皮细胞在形态和细胞行为上会变成成纤维细胞样，这表明Syndecan维持上皮细胞形态。Syndecan在发育过程中在数量、位置和结构上会发生变化：它最初出现在四细胞胚胎上（在其已知的基质配体之前），在着床前胚胎中局限于将形成胚胎本身的细胞，由于上皮 - 间充质相互作用（例如，输尿管芽在肾间充质中诱导）而改变其表达，以及随着细胞与细胞外基质的结合（例如，在B细胞分化期间），最终，在成熟组织中局限于上皮组织。其糖胺聚糖链的数量和大小随细胞形状和组织的变化而变化，产生组织类型特异性的Syndecan多态形式。它与影响细胞行为的主要细胞外效应分子的相互作用、其在维持细胞形状中的作用以及其在发育过程中的表达的时空变化表明Syndecan参与了形态发生。
