SNX32在细胞囊泡运输中的功能研究

精确的蛋白分选与转运对于维持细胞稳态至关重要。Sorting Nexin (SNX)家族是参与调控蛋白分选和囊泡运输的一类重要蛋白分子。我们通过对此亚家族的SNX32功能的初步研究发现，其主要定位于早期内吞体上，此外，SNX32与SNX6，VPS35以及CIMPR有较强的共定位。在HeLa中通过siRNA双敲除SNX32和其他SNX-BAR蛋白造成CIMPR在反式高尔基网络(TGN)上的分布减少。同时，我们发现SNX32和其他SNX-BAR蛋白存在相互作用，SNX32的缺失减少了SNX1和SNX6的早期内吞体定位并且使其蛋白水平下降，而SNX1和SNX6缺失后，SNX32却依然分布在蛋白分选的管囊状结构上。基于前期结果，我们提出假说，SNX32定位在早期内吞体膜上，招募和/或稳定SNX1-SNX6，组装SNX-BAR复合体及参与蛋白分选，调控了CIMPR从早期内吞体到高尔基体的运输。

Protein sorting and transport are essential for maintaining cell homeostasis. Disregulation of the intracellular sorting pathways leads to a range of diseases, including neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease, as well as various cardiovascular diseases. The Sorting Nexin (SNX) family is an important class of protein molecules involved in protein sorting and vesicle trafficking. We found that SNX32, a member of the SNX-BAR subfamily, is mainly localized to the early endosome, suggesting that it may be involved in endosomal protein sorting and trafficking. In addition, immunofluorescence co-staining with various organellar markers showed that SNX32 co-localizes with SNX6, VPS35 and CIMPR. Knock down of SNX32 in HeLa cells by siRNA reduced the distribution of CIMPR on the trans-Golgi network (TGN), revealing that it was involved in vesicular transport of CIMPR from early endosome to TGN. Meanwhile, we found that SNX32 interacts with other SNX-BAR proteins. Depletion of SNX32 reduces the association of SNX1 and SNX6 with early endosome and their protein levels. Intriguingly, in SNX1- or SNX6-depleted cells, SNX32 is still distributed on tubulovesicular sorting structures. Based on the above results, we hypothesize that SNX32 associates with early endosomes and plays a key role in SNX-BAR complex-mediated protein sorting and vesicular transport of CIMPR from early endosome to TGN by recruiting SNX6 and/or stabilizing the SNX1-SNX6 complex with the early endosome.