Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC - CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina.
Serviço de Microscopia Eletrônica, Centro de Pesquisas Gonçalo Moniz, Fiocruz-Ba, Brazil.
Traffic. 2017 Sep;18(9):604-621. doi: 10.1111/tra.12501.
Our understanding of protein and lipid trafficking in eukaryotic cells has been challenged by the finding of different forms of compartmentalization and cargo processing in protozoan parasites. Here, we show that, in the absence of a Golgi compartment in Giardia, proteins destined for secretion are directly sorted and packaged at specialized ER regions enriched in COPII coatomer complexes and ceramide. We also demonstrated that ER-resident proteins are retained at the ER by the action of a KDEL receptor, which, in contrast to other eukaryotic KDEL receptors, showed no interorganellar dynamic but instead acts specifically at the limit of the ER membrane. Our study suggests that the ER-exit sites and the perinuclear ER-membranes are capable of performing protein-sorting functions. In our view, the description presented here suggests that Giardia adaptation represents an extreme example of reductive evolution without loss of function.
我们对真核细胞中蛋白质和脂类运输的理解受到了挑战，因为在原生动物寄生虫中发现了不同形式的区室化和货物处理。在这里，我们表明，在贾第虫中没有高尔基体区室的情况下，用于分泌的蛋白质在富含 COPII 衣被复合物和神经酰胺的特殊 ER 区域被直接分拣和包装。我们还证明，内质网驻留蛋白通过 KDEL 受体被保留在内质网中，与其他真核 KDEL 受体不同，该受体没有细胞器间的动态，但相反专门作用于内质网膜的边界。我们的研究表明，内质网出口部位和核周内质网膜能够执行蛋白质分拣功能。在我们看来，这里提出的描述表明，贾第虫的适应代表了一种没有功能丧失的极端简化进化的例子。
