美国范德比尔特大学Ian G. Macara团队发现，高尔基体的尺寸过滤器调节顶膜蛋白的分选。2024年9月5日，《自然—细胞生物学》杂志在线发表了这一最新研究成果。

研究人员使用了合成生物学的方法来调查高尔基体的尺寸屏障是否会阻碍具有较大细胞质尾部的蛋白质的顶端分选。研究人员将Crb3、Ace2和Muc1作为代表性上皮蛋白，这些蛋白质具有较短的细胞质尾部。通过加入链霉亲和素结合肽，这些蛋白质可以在内质网中被捕获，直到加入生物素，这会触发同步释放到高尔基体，并随后转运到顶端皮质。引人注目的是，增加其细胞质区域的大小会导致部分错误定位到基底外侧皮质，并显著延迟高尔基体离开。

此外，“大”Crb3的N-糖基化被延迟，而“小”Crb3则分布在空间上不同的高尔基体区域。在生物学上，Crb3通过其细胞质尾部与Pals1蛋白形成复合体，这也可能延迟离开，但尽管在内质网和高尔基体处关联，Pals1在Crb3离开之前就解离了。值得注意的是，不可解离的突变体Pals1阻碍了Crb3的退出。研究人员得出意外的结论：高尔基体的尺寸过滤器促进了具有小细胞质区域的蛋白质的顶端分选，而Pals1的及时释放对于正常的Crb3分选至关重要。

研究人员表示，尽管经过数十年的研究，仍然对上皮膜蛋白的顶端分选理解不完全。人们注意到，顶端细胞质区域比基底外侧蛋白的细胞质区域小，但这种差异的原因尚不清楚。

附：英文原文

Title: A size filter at the Golgi regulates apical membrane protein sorting

Author: de Caestecker, Christian, Macara, Ian G.

Issue&Volume: 2024-09-05

Abstract: Despite decades of research, apical sorting of epithelial membrane proteins remains incompletely understood. We noted that apical cytoplasmic domains are smaller than those of basolateral proteins; however, the reason for this discrepancy is unknown. Here we used a synthetic biology approach to investigate whether a size barrier at the Golgi apparatus might hinder apical sorting of proteins with large cytoplasmic tails. We focused on Crb3, Ace2 and Muc1 as representative apical proteins with short cytoplasmic tails. By incorporating a streptavidin-binding peptide, these proteins can be trapped in the endoplasmic reticulum until addition of biotin, which triggers synchronous release to the Golgi and subsequent transport to the apical cortex. Strikingly, increasing the size of their cytoplasmic domains caused partial mislocalization to the basolateral cortex and significantly delayed Golgi departure. Moreover, N-glycosylation of ‘large’ Crb3 was delayed, and ‘small’ Crb3 segregated into spatially distinct Golgi regions. Biologically, Crb3 forms a complex through its cytoplasmic tail with the Pals1 protein, which could also delay departure, but although associated at the endoplasmic reticulum and Golgi, Pals1 disassociated before Crb3 departure. Notably, a non-dissociable mutant Pals1 hampered the exit of Crb3. We conclude that, unexpectedly, a size filter at the Golgi facilitates apical sorting of proteins with small cytoplasmic domains and that timely release of Pals1, to reduce cytoplasmic domain size, is essential for normal Crb3 sorting.

DOI: 10.1038/s41556-024-01500-0

Source: https://www.nature.com/articles/s41556-024-01500-0