Collins M K, Rozengurt E
J Cell Physiol. 1984 Feb;118(2):133-42. doi: 10.1002/jcp.1041180205.
Prolonged treatment of Swiss 3T3 cells with phorbol 12,13 dibutyrate (PDB) rendered the cells refractory to subsequent mitogenic stimulation by both PDB and vasopressin. In contrast, the cells retained full responsiveness to a wide variety of other mitogens. An early response to vasopressin and phorbol esters, inhibition of (125I)-labeled epidermal growth factor [(125I)-EGF] binding, was also substantially decreased in PDB pretreated cells. The cross desensitization was not produced by vasopressin; this ligand induced homologous but not heterologous desensitization. Exposure of Swiss 3T3 cells to PDB caused a down regulation of (3H)-PDB receptors but did not reduce the binding of vasopressin to refractory cells. The time-course (t1/2 = 7 h) and dependence on PDB concentration (half maximal at 20 nM) for this phorbol ester receptor loss paralleled the induction of the mitogenic desensitizations to both PDB and vasopressin. However, the time-course of recovery revealed an important dissociation between receptor presence and mitogenic response. When Swiss 3T3 cultures, which had been pretreated with PDB, were washed to remove this ligand and incubated in its absence for 24 h, both (3H)-PDB receptors and PDB or vasopressin inhibition of (125I)-EGF binding were almost completely restored to control levels. However the homologous and heterologous mitogenic desensitizations showed a very different reversal time. After a 24-h recovery period PDB-treated refractory cells were still unable to synthesize DNA in response to PDB or vasopressin. The mitogenic desensitizations were however completely reversible; after a 48-h incubation in the absence of PDB the cells responded fully to the mitogenic actions of PDB or vasopressin. This finding suggests that a further postreceptor step was also desensitized by prolonged PDB treatment. The presence of a low level of cycloheximide during the PDB pretreatment blocked induction of this postreceptor refractoriness. We propose that this refractory postreceptor step selectively blocks both PDB and vasopressin stimulation of DNA synthesis and may represent the point at which the mitogenic pathways of phorbol esters and vasopressin converge.
用佛波醇12,13 - 二丁酸酯（PDB）对瑞士3T3细胞进行长时间处理，会使细胞对随后PDB和血管加压素的促有丝分裂刺激产生抗性。相比之下，这些细胞对多种其他促有丝分裂原仍保持完全反应性。血管加压素和佛波醇酯的早期反应，即对（125I）标记的表皮生长因子[（125I）- EGF]结合的抑制，在PDB预处理的细胞中也显著降低。交叉脱敏不是由血管加压素引起的；这种配体诱导同源脱敏而非异源脱敏。将瑞士3T3细胞暴露于PDB会导致（3H）- PDB受体下调，但不会降低血管加压素与抗性细胞的结合。这种佛波醇酯受体丧失的时间进程（t1/2 = 7小时）以及对PDB浓度的依赖性（在20 nM时达到半数最大效应）与对PDB和血管加压素的促有丝分裂脱敏诱导平行。然而，恢复的时间进程显示受体存在与促有丝分裂反应之间存在重要的分离。当用PDB预处理的瑞士3T3培养物被洗涤以去除这种配体并在无配体的情况下孵育24小时时，（3H）- PDB受体以及PDB或血管加压素对（125I）- EGF结合的抑制几乎完全恢复到对照水平。然而，同源和异源促有丝分裂脱敏显示出非常不同的逆转时间。在24小时的恢复期后，PDB处理的抗性细胞仍然无法响应PDB或血管加压素合成DNA。然而，促有丝分裂脱敏是完全可逆的；在无PDB的情况下孵育48小时后，细胞对PDB或血管加压素的促有丝分裂作用完全反应。这一发现表明，长时间的PDB处理也使受体后进一步的步骤脱敏。在PDB预处理期间存在低水平的环己酰亚胺会阻止这种受体后抗性的诱导。我们提出，这种抗性的受体后步骤选择性地阻断PDB和血管加压素对DNA合成的刺激，并且可能代表佛波醇酯和血管加压素的促有丝分裂途径汇聚的点。
