Schubert D, LaCorbiere M
J Cell Biol. 1982 Jul;94(1):108-114. doi: 10.1083/jcb.94.1.108.
Both the skeletal muscle myoblast cell line L6 and an adhesion-deficient variant of L6 released glycoprotein complexes, termed adherons, into their culture medium. The adherons from the variant, M3A, differed from those of L6 in a number of properties. M3A adherons were much less effective in promoting the cell-substratum and cell-cell adhesion of myoblasts than L6 particles. The adherons from the two cell lines also differed in their relative sedimentation velocities in sucrose gradients and had different chemical compositions. The M3A particle lacked chondroitin and contained relatively less collagen and fibronectin than the L6 adheron. Both L6 and M3A particles adhered to plastic surfaces and cells equally well in the absence of calcium ions. Neither cell-cell adhesion nor particle aggregation occurred in calcium-free medium. However, in the presence of calcium, the L6 adherons aggregated completely and M3A particles aggregated poorly. These data suggest that at least two sets of interactions are required for adheron-mediated adhesion: a calcium-independent binding of the adheron to the cell, and a calcium-dependent interaction between particles that is directly responsible for adhesion. The M3A variant is blocked at the calcium-dependent step, resulting in an adhesion deficiency.
骨骼肌成肌细胞系L6及其黏附缺陷型变体L6均会向其培养基中释放一种称为黏附素的糖蛋白复合物。变体M3A的黏附素在许多特性上与L6的不同。M3A黏附素在促进成肌细胞与底物及细胞间黏附方面比L6颗粒的效果要差得多。这两种细胞系的黏附素在蔗糖梯度中的相对沉降速度也不同，且化学组成也不一样。M3A颗粒缺乏软骨素，与L6黏附素相比，其胶原蛋白和纤连蛋白含量相对较少。在没有钙离子的情况下，L6和M3A颗粒对塑料表面和细胞的黏附效果相同。在无钙培养基中，细胞间黏附及颗粒聚集均未发生。然而，在有钙离子存在的情况下，L6黏附素完全聚集，而M3A颗粒聚集较差。这些数据表明，黏附素介导的黏附至少需要两组相互作用：黏附素与细胞的钙非依赖性结合，以及颗粒之间直接负责黏附的钙依赖性相互作用。M3A变体在钙依赖性步骤受阻，导致黏附缺陷。
