Hoya Marta, Yanguas Francisco, Moro Sandra, Prescianotto-Baschong Cristina, Doncel Cristina, de León Nagore, Curto M-Ángeles, Spang Anne, Valdivieso M-Henar
Department of Microbiology and Genetics, Institute of Functional Biology and Genomics (IBFG), University of Salamanca, Consejo Superior de Investigaciones Científicas (CSIC), 37007, Spain.
Biozentrum, University of Basel, CH-4056, Switzerland.
Genetics. 2017 Feb;205(2):673-690. doi: 10.1534/genetics.116.193458. Epub 2016 Dec 14.
Despite its biological and medical relevance, traffic from the Golgi to the plasma membrane (PM) is one of the least understood steps of secretion. Exomer is a protein complex that mediates the trafficking of certain cargoes from the trans-Golgi network/early endosomes to the PM in budding yeast. Here, we show that in Schizosaccharomyces pombe the Cfr1 and Bch1 proteins constitute the simplest form of an exomer. Cfr1 co-immunoprecipitates with Assembly Polypeptide adaptor 1 (AP-1), AP-2, and Golgi-localized, gamma-adaptin ear domain homology, ARF-binding (GGA) subunits, and cfr1 interacts genetically with AP-1 and GGA genes. Exomer-defective cells exhibit multiple mild defects, including alterations in the morphology of Golgi stacks and the distribution of the synaptobrevin-like Syb1 protein, carboxypeptidase missorting, and stress sensitivity. S. pombe apm1Δ cells exhibit a defect in trafficking through the early endosomes that is severely aggravated in the absence of exomer. apm1Δ cfr1Δ cells exhibit a dramatic disorganization of intracellular compartments, including massive accumulation of electron-dense tubulovesicular structures. While the trans-Golgi network/early endosomes are severely disorganized in the apm1Δ cfr1Δ strain, gga21Δ gga22Δ cfr1Δ cells exhibit a significant disturbance of the prevacuolar/vacuolar compartments. Our findings show that exomer collaborates with clathrin adaptors in trafficking through diverse cellular compartments, and that this collaboration is important to maintain their integrity. These results indicate that the effect of eliminating exomer is more pervasive than that described to date, and suggest that exomer complexes might participate in diverse steps of vesicle transport in other organisms.
尽管其在生物学和医学方面具有相关性，但从高尔基体到质膜（PM）的转运是分泌过程中最不为人所理解的步骤之一。外排体是一种蛋白质复合物，它介导某些货物从反式高尔基体网络/早期内体向出芽酵母中的质膜转运。在这里，我们表明在粟酒裂殖酵母中，Cfr1和Bch1蛋白构成了外排体的最简单形式。Cfr1与装配多肽衔接蛋白1（AP-1）、AP-2以及高尔基体定位的γ衔接蛋白耳结构域同源物、ARF结合（GGA）亚基共免疫沉淀，并且cfr1与AP-1和GGA基因发生遗传相互作用。外排体缺陷细胞表现出多种轻微缺陷，包括高尔基体堆叠形态的改变、突触融合蛋白样Syb1蛋白的分布变化、羧肽酶分选错误以及应激敏感性。粟酒裂殖酵母apm1Δ细胞在通过早期内体的转运中存在缺陷，在没有外排体的情况下这种缺陷会严重加剧。apm1Δ cfr1Δ细胞表现出细胞内区室的剧烈紊乱，包括电子致密的管状小泡结构的大量积累。虽然反式高尔基体网络/早期内体在apm1Δ cfr1Δ菌株中严重紊乱，但gga21Δ gga22Δ cfr1Δ细胞表现出前液泡/液泡区室的显著紊乱。我们的研究结果表明，外排体在通过不同细胞区室的转运中与网格蛋白衔接蛋白协作，并且这种协作对于维持它们的完整性很重要。这些结果表明，消除外排体的影响比迄今为止所描述的更为普遍，并表明外排体复合物可能参与其他生物体中囊泡运输的不同步骤。
