Tracking exocytosis of a GPI-anchored protein in Aspergillus nidulans.,Traffic

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Tracking exocytosis of a GPI-anchored protein in Aspergillus nidulans.
Traffic ( IF 3.6 ) Pub Date : 2020-09-09 , DOI: 10.1111/tra.12761
Miguel A Peñalva ₁ , Esteban Moscoso-Romero _{1,

2} , Miguel Hernández-González _{1,

3}

Affiliation

Secretion of the glycosylphosphatidylinositol‐anchored protein (GPI‐AP) EglC was investigated in the filamentous fungus Aspergillus nidulans, exploiting a sucrose‐inducible promoter to conditionally express the protein in cells blocked at different steps of exocytosis. EglC is delivered to the cell surface in a polarized fashion, but appears to redistribute rapidly toward apico‐distal regions. Inactivation of SarA^Sar1 mediating COPII vesicle biogenesis resulted in the accumulation of EglC in the endoplasmic reticulum (ER) but, rather than concentrating in ER‐exit‐sites, the reporter labeled the ER uniformly. Abnormal posttranslational modifications of EglC were detected in sarAts and sed5ts mutants, suggesting that blocking COPII biogenesis or traffic in the ER/Golgi interface might affect GPI remodeling. EglC delivery to the plasma membrane requires, besides Golgi function, the TRAPPII complex mediating the biogenesis of RAB11 secretory vesicles at the TGN, but is unaffected by the absence of RAB5, the key regulator of early endosome biogenesis/maturation. Thus, unlike the soluble extracellular enzyme inulinase, EglC is directly delivered from the TGN to the plasma membrane without involvement of endosomes. We conclude that in A. nidulans, GPI‐APs follow a direct secretory pathway from the ER to the plasma membrane.

中文翻译：

追踪构巢曲霉中GPI锚定蛋白的胞吐作用。

在丝状真菌构巢曲霉中研究了糖基磷脂酰肌醇锚定蛋白（GPI-AP）EglC的分泌，利用蔗糖诱导型启动子在胞吐不同步骤受阻的细胞中有条件表达该蛋白。EglC以极化的方式传递到细胞表面，但似乎会迅速向蜂巢远端区域重新分布。SarA ^Sar1的失活介导了COPII囊泡的生物发生，导致EglC在内质网（ER）中积累，但不是集中在ER出口位点，而是统一标记ER。在sarAts和sed5ts中检测到EglC的翻译后修饰异常突变体，表明在ER /高尔基体中阻断COPII的生物发生或运输可能会影响GPI重塑。EglC传递到质膜，除了高尔基体功能外，还需要TRAPPII复合物在TGN处介导RAB11分泌囊泡的生物发生，但不受RAB5缺乏的影响，RAB5是早期内体生物发生/成熟的关键调节剂。因此，与可溶性细胞外酶菊粉酶不同，EglC直接从TGN传递到质膜，而没有内体参与。我们得出结论，在构巢曲霉中，GPI-APs从ER到质膜遵循直接的分泌途径。

更新日期：2020-11-09

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