Cao Shu-Ya,Liu Yi-Shi,Gao Xiao-Dong,Kinoshita Taroh,Fujita Morihisa
Protein modification by glycosylphosphatidylinositol (GPI) takes place in the endoplasmic reticulum (ER). GPI-anchored proteins (GPI-APs) formed in the ER are transported to the cell surface through the Golgi apparatus. During transport, the GPI-anchor structure is processed. In most cells, an acyl chain modified to the inositol of GPI is removed by a GPI-inositol deacylase, PGAP1, in the ER. Inositol-deacylated GPI-APs become sensitive to bacterial phosphatidylinositol-specific phospholipase C (PI-PLC). We previously reported that GPI-APs are partially resistant to PI-PLC when PGAP1 activity is weakened by the deletion of selenoprotein T (SELT) or cleft lip and palate transmembrane protein 1 (CLPTM1). In this study, we found that the loss of TMEM41B, an ER-localized lipid scramblase, restored PI-PLC sensitivity of GPI-APs in SELT-knockout (KO) and CLPTM1-KO cells. In TMEM41B-KO cells, the transport of GPI-APs as well as transmembrane proteins from the ER to the Golgi was delayed. Furthermore, the turnover of PGAP1, which is mediated by ER-associated degradation, was slowed in TMEM41B-KO cells. Taken together, these findings indicate that inhibition of TMEM41B-dependent lipid scrambling promotes GPI-AP processing in the ER through PGAP1 stabilization and slowed protein trafficking.
Huan Li,Jie Yang,Jingfeng Li,Zhenxing Gao,Jiang Xu,Chaoyang Li
Summary Defects of glycosylphosphatidylinositol (GPI)-anchor synthesis lead to the production of pro-proteins with altered functions. However, pro-protein-specific antibodies for functional analysis are lacking. Here, we present a protocol to differentiate GPI-anchored prion protein (PrP) from pro-PrP in cancer cells using a complementary approach applicable to other GPI-anchored proteins. We first describe steps for phosphatidylinositol-specific phospholipase C treatment and flow-cytometry-based detection. We then detail the carboxypeptidase Y (CPDY) assay including antibody immobilization, affinity purification, CPDY treatment, and western-blot-based detection. For complete details on the use and execution of this protocol, please refer to Li et al. (2022). 1
Min Li,Zhenfang Shang,Yonglan Ma,Huijun Zhao,Zhijing Ni,Zhaojun Wei,Xiu Zhang
This study investigates the growth tolerance mechanisms ofChlorella pyrenoidosato 3-fluorophenol and its removal efficiency by algal cells. Our results indicate thatC. pyrenoidosacan tolerate up to 100 mg/L of 3-fluorophenol, exhibiting a significant hormesis effect characterized by initial inhibition followed by promotion of growth. InC. pyrenoidosacells, the activities of superoxide dismutase (SOD) and catalase (CAT), as well as the levels of malondialdehyde (MDA) and reactive oxygen species (ROS), were higher than or comparable to the control group. Metabolic analysis revealed that the 3-fluorophenol treatment activated pathways, such as glycerol phospholipid metabolism, autophagy, glycosylphosphatidylinositol (GPI)-anchored protein biosynthesis, and phenylpropanoid biosynthesis, contributed to the stabilization of cell membrane structures and enhanced cell repair capacity. After 240 h of treatment, over 50% of 3-fluorophenol was removed by algal cells, primarily through adsorption. Thus,C. pyrenoidosashows potential as an effective biosorbent for the bioremediation of 3-fluorophenol.
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