分泌蛋白,包括质膜蛋白质,通常已知通过内质网至高尔基体途径转运至质膜。然而,最近的研究表明,几种缺乏信号肽的质膜蛋白和胞质蛋白通过非常规蛋白分泌(UcPS)途径释放,在前往细胞表面的途中绕过高尔基.例如,已观察到跨膜蛋白,例如错误折叠的囊性纤维化跨膜传导调节因子(CFTR)蛋白和冠状病毒的Spike蛋白在细胞应激条件下通过UcPS途径到达细胞表面。然而,UcPS途径的精确机制,特别是涉及细胞溶质运动蛋白的分子机制,基本上是未知的。在这项研究中,我们确定了特定的驱动蛋白,即KIF1A和KIF5A,连同细胞质动力蛋白,作为CFTR和SARS-CoV-2Spike蛋白非常规贩运的关键参与者。基因沉默结果表明KIF1A的敲低,KIF5A,和KIF相关的衔接蛋白SKIP,FYCO1显著降低△F508-CFTR的UcPS。此外,这些运动蛋白的基因沉默阻碍了SARS-CoV-2Spike蛋白的UcPS。然而,相同的基因沉默并不影响野生型CFTR和Spike蛋白的常规Gogimediated细胞表面运输。这些发现表明,特定的运动蛋白,与参与传统贩运的人不同,与应激诱导的跨膜蛋白UcPS有关。
Secretory proteins, including plasma membrane proteins, are generally known to be transported to the plasma membrane through the endoplasmic reticulum- to-Golgi pathway. However, recent studies have revealed that several plasma membrane proteins and cytosolic proteins lacking a signal peptide are released via an unconventional protein secretion (UcPS) route, bypassing the Golgi during their journey to the cell surface. For instance, transmembrane proteins such as the misfolded cystic fibrosis transmembrane conductance regulator (
CFTR) protein and the Spike protein of coronaviruses have been observed to reach the cell surface through a UcPS pathway under cell stress conditions. Nevertheless, the precise mechanisms of the UcPS pathway, particularly the molecular machineries involving cytosolic motor proteins, remain largely unknown. In this study, we identified specific kinesins, namely KIF1A and KIF5A, along with cytoplasmic dynein, as critical players in the unconventional trafficking of
CFTR and the SARS-CoV-2 Spike protein. Gene silencing results demonstrated that knockdown of KIF1A, KIF5A, and the KIF-associated adaptor protein SKIP, FYCO1 significantly reduced the UcPS of △F508-
CFTR. Moreover, gene silencing of these motor proteins impeded the UcPS of the SARS-CoV-2 Spike protein. However, the same gene silencing did not affect the conventional Golgimediated cell surface trafficking of wild-type
CFTR and Spike protein. These findings suggest that specific motor proteins, distinct from those involved in conventional trafficking, are implicated in the stress-induced UcPS of transmembrane proteins.