Bascom C C, Sharifi B G, Johnson T C
J Cell Biochem. 1987 Aug;34(4):283-91. doi: 10.1002/jcb.240340407.
The control of cell proliferation involves the complex interaction between growth factors and growth inhibitors. We have examined this interaction with the mitogen epidermal growth factor (EGF) and a recently purified 18 kD, pI 3, sialoglycopeptide that reversibly inhibits cellular metabolism of a variety of cells. The sialoglycopeptide was a very potent inhibitor of EGF action; 0.22 nM of the inhibitor completely blocked the mitogenic effect of 1.60 nM of EGF. The sialoglycopeptide, however, did not affect the binding of EGF to 3T3 cells. Neither the mixed affinities (0.11-1.9 nM) of binding nor the total number of receptors (50,000 receptors/cell) for EGF were altered by the addition of the sialoglycopeptide. In addition, competitive binding experiments demonstrated the specificity of inhibitor binding to 3T3 cells and also showed that EGF and the sialoglycopeptide did not share the same receptor, suggesting that the inhibitor blocked EGF action at a postreceptor, intracellular event in the signal cascade. We further demonstrated that the sialoglycopeptide had to be added within 2.5 hr after EGF to block effectively the stimulation of DNA synthesis by the growth factor, suggesting that the inhibitor blocked EGF stimulation at a relatively early step in the signal transduction mechanism.
细胞增殖的控制涉及生长因子与生长抑制剂之间复杂的相互作用。我们已使用促分裂原表皮生长因子（EGF）以及最近纯化的一种18 kD、pI 3的唾液酸糖肽来研究这种相互作用，该唾液酸糖肽可可逆地抑制多种细胞的细胞代谢。这种唾液酸糖肽是EGF作用的一种非常有效的抑制剂；0.22 nM的抑制剂可完全阻断1.60 nM EGF的促有丝分裂作用。然而，该唾液酸糖肽并不影响EGF与3T3细胞的结合。添加唾液酸糖肽既不改变结合的混合亲和力（0.11 - 1.9 nM），也不改变EGF受体的总数（50,000个受体/细胞）。此外，竞争性结合实验证明了抑制剂与3T3细胞结合的特异性，还表明EGF和唾液酸糖肽不共享相同的受体，这表明该抑制剂在信号级联反应的受体后、细胞内事件中阻断了EGF的作用。我们进一步证明，唾液酸糖肽必须在EGF加入后的2.5小时内添加，才能有效阻断生长因子对DNA合成的刺激，这表明该抑制剂在信号转导机制的相对早期步骤阻断了EGF的刺激。
