Fuller C M, Bridges R J, Benos D J
Department of Physiology and Biophysics, University of Alabama at Birmingham 35294.
Am J Physiol. 1994 Mar;266(3 Pt 1):C661-8. doi: 10.1152/ajpcell.1994.266.3.C661.
Several transport proteins are known to be trafficked to the cell membrane in response to appropriate secretagogues. In several cases, the response has been shown to be dependent on the cytoskeleton. We tested the hypothesis that the forskolin- and/or ionomycin-sensitive Cl- secretory response in colonic epithelia is dependent on an intact cytoskeleton. Using 125I- efflux as an assay for Cl- transport in the colonic epithelial cell line T84, we found that preincubation of the tissue for 3 h with either of two inhibitors of microtubule polymerization, nocodazole or colchicine, disrupted the cellular tubulin architecture and also reduced the forskolin- but not the ionomycin-evoked I- efflux. In contrast, brief exposure (4 min) to nocodazole was without effect on the forskolin-sensitive efflux, suggesting that the drug is not acting to block the stimulus-response pathway. An inactive structural analogue of colchicine, beta-lumicolchicine, had no inhibitory effect on either the forskolin-sensitive efflux or on microtubular structure. In a second model of Cl- secretion, the stripped rat colon, both colchicine and nocodazole reduced the forskolin-dependent short-circuit current by an average of 30-40%, suggesting a similar mechanism for insertion of Cl- channels into the plasma membrane. These findings suggest that the Cl- secretory response is dependent on microtubules and has a physiological role in the adenosine 3',5'-cyclic monophosphate-dependent, but not the Ca(2+)-dependent, Cl- secretion in colonic epithelia.
已知几种转运蛋白会在适当的促分泌剂作用下被转运至细胞膜。在多种情况下，已证明这种反应依赖于细胞骨架。我们测试了这样一个假设：结肠上皮细胞中对福斯高林和/或离子霉素敏感的氯离子分泌反应依赖于完整的细胞骨架。使用¹²⁵I外流作为结肠上皮细胞系T84中氯离子转运的检测方法，我们发现用两种微管聚合抑制剂（诺考达唑或秋水仙碱）之一对组织进行3小时预孵育，会破坏细胞微管蛋白结构，同时也会降低福斯高林诱发的碘外流，但不会降低离子霉素诱发的碘外流。相比之下，短暂暴露（4分钟）于诺考达唑对福斯高林敏感的外流没有影响，这表明该药物并非通过阻断刺激 - 反应途径起作用。秋水仙碱的一种无活性结构类似物β - 光秋水仙碱，对福斯高林敏感的外流或微管结构均无抑制作用。在氯离子分泌的第二个模型——去黏膜大鼠结肠中，秋水仙碱和诺考达唑均使福斯高林依赖性短路电流平均降低30 - 40%，这表明氯离子通道插入质膜的机制类似。这些发现表明，氯离子分泌反应依赖于微管，并且在结肠上皮细胞中对腺苷3',5'-环磷酸依赖性而非钙离子依赖性的氯离子分泌具有生理作用。
