Constitutive secretion of serum albumin requires reversible protein tyrosine phosphorylation events in trans-Golgi
Constitutive secretion of serum albumin requires reversible protein tyrosine phosphorylation events in trans-Golgi
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DOI：
10.1152/ajpcell.00019.2005
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发表时间：
2005-09-01
影响因子：
5.5
通讯作者：
Thomas, GMH
中科院分区：
文献类型：
--
作者：
Webb, RJ;Judah, JD;Thomas, GMH
大鼠肝细胞的血清白蛋白分泌通过组成性途径进行。尽管对蛋白质酪氨酸磷酸化在调节分泌中的作用了解很多，但对其在组成性过程中的功能却一无所知。在这里，我们表明，白蛋白分泌抑制酪氨酸激酶抑制剂染料木素，但相对不敏感的亚型选择性抑制剂或治疗。酪氨酸磷酸酶抑制剂过钒酸盐和双过氧（1，10-菲咯啉）-氧钒酸盐也以生理学上相同的方式阻断分泌。激酶或磷酸酶的抑制导致白蛋白在反式高尔基体和质膜之间积累，而直接前体前白蛋白在近端隔室中积累。反式高尔基体标记TGN 38在抑制酪氨酸磷酸酶作用的条件下迅速分散，而顺式高尔基体标记GM 130的分布对染料木素或过钒酸盐不敏感。通过使用特异性反应生物素化探针，我们检测到蛋白酪氨酸磷酸酶在高度纯化的大鼠肝高尔基体膜。这些膜还含有内源性酪氨酸激酶及其底物，表明可逆酪氨酸磷酸化的酶和底物是该运输室的正常膜驻留组分。在肌动蛋白丝和微管的扰动的情况下，我们得出结论，可逆的蛋白质酪氨酸磷酸化的trans-Golgi网络是必不可少的白蛋白分泌，并提出白蛋白的组成性分泌实际上是一个受调节的过程。
Serum albumin secretion from rat hepatocytes proceeds via the constitutive pathway. Although much is known about the role of protein tyrosine phosphorylation in regulated secretion, nothing is known about its function in the constitutive process. Here we show that albumin secretion is inhibited by the tyrosine kinase inhibitor genistein but relatively insensitive to subtype-selective inhibitors or treatments. Secretion is also blocked in a physiologically identical manner by the tyrosine phosphatase inhibitors pervanadate and bisperoxo(1,10-phenanthroline)-oxovanadate. Inhibition of either the kinase(s) or phosphatase(s) leads to the accumulation of albumin between the trans-Golgi and the plasma membrane, whereas the immediate precursor proalbumin builds up in a proximal compartment. The trans-Golgi marker TGN38 is rapidly dispersed under conditions that inhibit tyrosine phosphatase action, whereas the distribution of the cis-Golgi marker GM130 is insensitive to genistein or pervanadate. By using a specifically reactive biotinylation probe, we detected protein tyrosine phosphatases in highly purified rat liver Golgi membranes. These membranes also contain both endogenous tyrosine kinases and their substrates, indicating that enzymes and substrates for reversible tyrosine phosphorylation are normal membrane-resident components of this trafficking compartment. In the absence of perturbation of actin filaments and microtubules, we conclude that reversible protein tyrosine phosphorylation in the trans-Golgi network is essential for albumin secretion and propose that the constitutive secretion of albumin is in fact a regulated process.