Syntaxin-6 SNARE involvement in secretory and endocytic pathways of cultured pancreatic β-cells
Syntaxin-6 SNARE involvement in secretory and endocytic pathways of cultured pancreatic β-cells
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DOI：
10.1091/mbc.e03-08-0554
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发表时间：
2004-04-01
影响因子：
3.3
通讯作者：
Arvan, P
中科院分区：
文献类型：
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作者：
Kuliawat, R;Kalinina, E;Arvan, P
在胰腺β细胞中，Synaxin 6(Syn6)可溶性N-乙基马来酰亚胺敏感因子附着蛋白受体分布于跨高尔基网络(TGN)(外溢到未成熟的分泌颗粒)和内小体中。在分泌颗粒的生物发生中可能需要Syn6，但Syn6在活的调节分泌细胞中的作用尚不清楚。我们已经在INS-1β细胞系中建立了一个蜕皮激素诱导的基因表达系统，并发现诱导表达一种无膜锚的胞质Syn6(称为Syn6t)，但不是全长Syn6，导致这些细胞中内体递送到溶酶体和TGN的显著缺陷。该缺陷发生在转铁蛋白循环所涉及的内体支点的下游，以及甘露糖6-磷酸受体稳态分布的上游。相比之下，刺激能力的获得和β颗粒的最终大小都不受影响。显性干扰Syn6的生物合成效应似乎仅限于减缓对胰岛素的颗粒内加工(在2小时内达到正常水平)和对新合成的溶酶体原酶的分选造成轻微干扰。我们得出结论，Syn6t突变体的表达减缓了内体成熟的限速步骤，但仅对调节的和结构性的分泌途径以及溶酶体酶的TGN分选提供了轻微的和潜在的间接干扰。
In pancreatic beta-cells, the syntaxin 6 (Syn6) soluble N-ethylmaleimide-sensitive factor attachment protein receptor is distributed in the trans-Golgi network (TGN) (with spillover into immature secretory granules) and endosomes. A possible Syn6 requirement has been suggested in secretory granule biogenesis, but the role of Syn6 in live regulated secretory cells remains unexplored. We have created an ecdysone-inducible gene expression system in the INS-1 beta-cell line and find that induced expression of a membrane-anchorless, cytosolic Syn6 (called Syn6t), but not full-length Syn6, causes a prominent defect in endosomal delivery to lysosomes, and the TGN, in these cells. The defect occurs downstream of the endosomal branchpoint involved in transferrin recycling, and upstream of the steady-state distribution of mannose 6-phosphate receptors. By contrast, neither acquisition of stimulus competence nor the ultimate size of beta-granules is affected. Biosynthetic effects of dominant-interfering Syn6 seem limited to slowed intragranular processing to insulin (achieving normal levels within 2 h) and minor perturbation of sorting of newly synthesized lysosomal proenzymes. We conclude that expression of the Syn6t mutant slows a rate-limiting step in endosomal maturation but provides only modest and potentially indirect interference with regulated and constitutive secretory pathways, and in TGN sorting of lysosomal enzymes.