Vesicles trafficking including secretory vesicles and autophagy have an essential role of numerous biological functions such as cell growth, cellular communication, cell metabolism, and intracellular homeostasis. The E3 ubiquitin ligase membrane-associated ring-CH-type finger 2 (MARCH2) is well known to regulate the vesicular trafficking of its substrates such as DLG1, beta2-adrenergic receptors, Cystic fibrosis transmembrane conductance regulator (CFTR), and Dishevelled. However, its role of secretory pathway between endoplasmic reticulum (ER) and Golgi compartments have not been reported yet. Here I examined novel substrate of MARCH2 using proximity-dependent biotinylation assay and identified the ER-Golgi intermediate compartment protein 3 (ERGIC3).
MARCH2 degrades ERGIC3 by ubiquitination, proteasome, and lysosome dependent manner. I further found that α1-antitrypsin and haptoglobin interact with ERGIC3 and that ERGIC3 regulates their secretion. Furthermore, MARCH2-mediated ERGIC3 ubiquitination is the key role in trafficking of ERGIC3-binding secretory proteins. These results reveal that ERGIC3 is a novel cargo receptor for secretion of α1-antitrypsin and haptoglobin and its ubiquitination by MARCH2 is a crucial role in the early secretory pathway of α1-antitrypsin and haptoglobin.
Lysosome-dependent degradation such as autophagy and endocytosis is crucial role for recycling cellular components to maintain intracellular homeostasis. Recently, Study on regulation of lysosomal function is important to develop clinical drug for cancer, crohn’s, and neurodegenerative diseases. In this study, I also found that JS-K as a Nitric oxide-releasing prodrug affected to autophagy process through the lysosomal dysfunction. JS-K impaired degradation of autophagosome and endocytosis-mediated degradation of epidermal growth factor receptors (EGFR). JS-K increased reactive oxygen species (ROS) stress by glutathione (GSH) depletion and releasing NO. In addition, JS-K promoted lysosomal membrane permeabilization by GSH depletion-mediated ROS stress. Surprisingly, blocking the fusion of autophagosome-lysosome fusion prevented JS-K-mediated LMP. These my findings suggest that depletion of GSH-mediated LMP possibly can be useful to develop the therapeutic target for anti-cancer drug and autophagosome-lysosome fusion is essential for LDCD caused by LMP.