The Xenopus Oocyte as an Expression System for Functional Analyses of Fish Aquaporins.

Aquaporins are membrane proteins present in all organisms that selectively transport water and small, uncharged solutes across biological membranes along an osmotic gradient. Recent gene editing technologies in zebrafish (Danio rerio) have started to uncover the physiological functions of the aquaporins in teleosts, but these approaches require methods to establish the effects of specific mutations on channel function. The oocytes of the South African frog Xenopus laevis are widely used for the expression of bacterial, plant, and animal aquaporins, and this heterologous system has contributed to numerous discoveries in aquaporin biology. This chapter focuses on techniques used for oocyte preparation and aquaporin expression and gives an overview of specific methods to determine water and solute permeability of the channels and their intracellular trafficking in oocytes.

Blockade of IGF/IGF-1R signaling axis with soluble IGF-1R mutants suppresses the cell proliferation and tumor growth of human osteosarcoma.

Primary bone tumor, also known as osteosarcoma (OS), is the most common primary malignancy of bone in children and young adults. Current treatment protocols yield a 5-year survival rate of near 70% although approximately 80% of patients have metastatic disease at the time of diagnosis. However, long-term survival rates have remained virtually unchanged for nearly four decades, largely due to our limited understanding of the disease process. One major signaling pathway that has been implicated in human OS tumorigenesis is the insulin-like growth factor (IGF)/insulin-like growth factor-1 receptor (IGF1R) signaling axis. IGF1R is a heterotetrameric α2ß2 receptor, in which the α subunits comprise the ligand binding site, whereas the ß subunits are transmembrane proteins containing intracellular tyrosine kinase domains. Although numerous strategies have been devised to target IGF/IGF1R axis, most of them have failed in clinical trials due to the lack of specificity and/or limited efficacy. Here, we investigated whether a more effective and specific blockade of IGF1R activity in human OS cells can be accomplished by employing dominant-negative IGF1R (dnIGF1R) mutants. We engineered the recombinant adenoviruses expressing two IGF1R mutants derived from the α (aa 1-524) and ß (aa 741-936) subunits, and found that either dnIGF1Rα and/or dnIGF1Rß effectively inhibited cell migration, colony formation, and cell cycle progression of human OS cells, which could be reversed by exogenous IGF1. Furthermore, dnIGF1Rα and/or dnIGF1Rß inhibited OS xenograft tumor growth in vivo, with the greatest inhibition of tumor growth shown by dnIGF1Rα. Mechanistically, the dnIGF1R mutants down-regulated the expression of PI3K/AKT and RAS/RAF/MAPK, BCL2, Cyclin D1 and most EMT regulators, while up-regulating pro-apoptotic genes in human OS cells. Collectively, these findings strongly suggest that the dnIGF1R mutants, especially dnIGF1Rα, may be further developed as novel anticancer agents that target IGF signaling axis with high specificity and efficacy.

Valosin-containing protein VCP/p97 is essential for the intracellular development of Leishmania and its survival under heat stress.

Valosin-containing protein (VCP)/p97/Cdc48 is one of the best-characterised type II cytosolic AAA+ ATPases most known for their role in ubiquitin-dependent protein quality control. Here, we provide functional insights into the role of the Leishmania VCP/p97 homologue (LiVCP) in the parasite intracellular development. We demonstrate that although LiVCP is an essential gene, Leishmania infantum promastigotes can grow with less VCP. In contrast, growth of axenic and intracellular amastigotes is dramatically affected upon decreased LiVCP levels in heterozygous and temperature sensitive (ts) LiVCP mutants or the expression of dominant negative mutants known to specifically target the second conserved VCP ATPase domain, a major contributor of the VCP overall ATPase activity. Interestingly, these VCP mutants are also unable to survive heat stress, and a ts VCP mutant is defective in amastigote growth. Consistent with LiVCP's essential function in amastigotes, LiVCP messenger ribonucleic acid undergoes 3'Untranslated Region (UTR)-mediated developmental regulation, resulting in higher VCP expression in amastigotes. Furthermore, we show that parasite mutant lines expressing lower VCP levels or dominant negative VCP forms exhibit high accumulation of polyubiquitinated proteins and increased sensitivity to proteotoxic stress, supporting the ubiquitin-selective chaperone function of LiVCP. Together, these results emphasise the crucial role LiVCP plays under heat stress and during the parasite intracellular development.

The inhibitory effects on hepatitis B virus gene expression in stable expression of DN mutants of hepatitis B virus X gene / 中华传染病杂志

Objective The newly developing gene therapy method and dominant negative mutants were bein g used as new promising HBV therapy method, and a dominant negative mutant of HB V X g ene we have reported in our previous report has some effects both on HBV replica tion and expression in transient expression, but the effects were interfered by persistent secretion of HBV in HepG 2 2.2.15 cell line in the experiment. To mak e sure the effects of dominant negative mutant of HBx gene, we established a HBx DN stably expressing cell clone, and evaluated the effects of HBx dominant negat ive mutant on HBV gene expression. Methods The prev HBx-GFP dominant mutant and the plasmids pRev Xwt, pRev GFP which contain the wild type X gene or GFP gene then transfected into HepG 2 2.2.15 cells by liposome. The HBsAg, HBeAg by in media were as sayed by RIA and HBV-related RNA were assayed by Northern blot. Results The pRev HBx-GFP, GFP and wild type X constructs can be effectively expressed in HepG 2 2.2.15 cells. The stable expressed HBx -GFP can significantly reduce HBeAg, HBeAg in media and the HBV-related RNA in HepG 2 2.2.15 cells, but not for pRev Xwt and pRev GFP. Conclusions The dominant negative mutant pRev HBx-GFP can significantly inhibit the HBV gen e expression. It also suggested that X gene may be one promising target for HBV gene therapy.