Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff, CF24 4LU, UK.
Structure. 2010 Feb 10;18(2):239-45. doi: 10.1016/j.str.2009.11.013.
Interactions between collagens and proteoglycans help define the structure and function of extracellular matrices. The cornea, which contains proteoglycans with keratan sulphate or chondroitin/dermatan sulphate glycosaminoglycan chains, is an excellent model system in which to study collagen-proteoglycan structures and interactions. Here, we present the first three-dimensional electron microscopic reconstructions of the cornea, and these include corneas from which glycosaminoglycans have been selectively removed by enzymatic digestion. Our reconstructions show that narrow collagen fibrils associate with sulphated proteoglycans that appear as extended, variable-length linear structures. The proteoglycan network appears to tether two or more collagen fibrils, and thus organize the matrix with enough spatial specificity to fulfill the requirements for corneal transparency. Based on the data, we propose that the characteristic pseudohexagonal fibril arrangement in cornea is controlled by the balance of a repulsive force arising from osmotic pressure and an attractive force due to the thermal motion of the proteoglycans.
胶原和蛋白聚糖之间的相互作用有助于确定细胞外基质的结构和功能。角膜富含带有硫酸角质素或硫酸软骨素/硫酸皮肤素糖胺聚糖链的蛋白聚糖，是研究胶原-蛋白聚糖结构和相互作用的极佳模型系统。在这里，我们首次呈现了角膜的三维电子显微镜重建图，其中包括通过酶消化选择性去除糖胺聚糖的角膜。我们的重建图表明，狭窄的胶原原纤维与看起来呈伸展的、长度可变的线性结构的硫酸化蛋白聚糖结合。蛋白聚糖网络似乎固定了两个或更多的胶原原纤维，从而以足够的空间特异性组织基质，以满足角膜透明度的要求。基于这些数据，我们提出角膜中特征性的伪六边形纤维排列是由渗透压产生的排斥力和蛋白聚糖热运动产生的吸引力之间的平衡控制的。
