Procollagen secretion meets the minimum requirements for the rate-controlling step in the ascorbate induction of procollagen synthesis.
Procollagen secretion meets the minimum requirements for the rate-controlling step in the ascorbate induction of procollagen synthesis.
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DOI：
10.1016/s0021-9258(18)89470-4
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发表时间：
1985-03
期刊：
影响因子：
--
通讯作者：
R. I. Schwarz
中科院分区：
文献类型：
--
作者：
R. I. Schwarz
先前的研究表明，在原代禽类肌腱细胞中添加抗坏血酸可导致前胶原翻译增加约6倍，在4小时后首次观察到，并在48小时后达到最大水平。同样，在添加抗坏血酸后，前胶原mRNA从12小时开始增加约6倍，并在72小时达到最大水平。前胶原分泌的速率常数现在也被证明与抗坏血酸发生6倍的变化。这导致细胞内原胶原的半衰期从120分钟下降到20分钟。与前胶原通路的其他步骤形成鲜明对比的是，分泌速率常数的变化在不到30分钟的时间内发生得非常快。此外，加入抗坏血酸后，体内80%以上的前胶原蛋白可以快速分泌。由于这种变化是由脯氨酸残基羟基化的增加引起的，而且羟基化反应已经局限于内质网，因此这一证据有力地支持了分泌途径中缓慢的一步是运输出内质网的模型。[3H]脯氨酸标记细胞的电镜放射自显像进一步支持了这一观点，其中细胞内标记的前胶原池高度定位于内质网。
Ascorbate addition to primary avian tendon cells has been shown previously to cause a approximately 6-fold increase in procollagen translation that is first observable after 4 h and reaches a maximum level after 48 h. Similarly, procollagen mRNA has been shown to increase after ascorbate addition by approximately 6-fold starting at 12 h and reaching a maximum level by 72 h. The rate constant for procollagen secretion is now shown to also react to ascorbate by a 6-fold change. This results in a drop in the half-life of procollagen within the cell from 120 to 20 min. In sharp contrast to the other steps in the procollagen pathway, the change in the secretion rate constant is extremely fast occurring in less than 30 min. Moreover, after ascorbate addition, greater than 80% of the internal procollagen can be secreted at the fast rate. Since this change results from an increase in hydroxylation of proline residues and since the hydroxylation reaction has been localized to the endoplasmic reticulum, this evidence strongly supports the model that the slow step in the secretion pathway is transport out of the endoplasmic reticulum. Further support for this comes from electron microscope autoradiography of [3H]proline-labeled cells where the labeled procollagen pool within the cells was highly localized to the endoplasmic reticulum.