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1. Receptor interacting protein kinase 3 (RIP3) regulates iPSCs generation through modulating cell cycle progression genes

Author

Ahmad Al-Moujahed, Bo Tian, Nikolaos E. Efstathiou, Eleni K. Konstantinou, Mien Hoang, Haijiang Lin, Joan W. Miller, and Demetrios G. Vavvas

Subjects
Biology (General), QH301-705.5
Abstract

The molecular mechanisms involved in induced pluripotent stem cells (iPSCs) generation are poorly understood. The cell death machinery of apoptosis-inducing caspases have been shown to facilitate the process of iPSCs reprogramming. However, the effect of other cell death processes, such as programmed necrosis (necroptosis), on iPSCs induction has not been studied. In this study, we investigated the role of receptor-interacting protein kinase 3 (RIP3), an essential regulator of necroptosis, in reprogramming mouse embryonic fibroblast cells (MEFs) into iPSCs. RIP3 was found to be upregulated in iPSCs compared to MEFs. Deletion of RIP3 dramatically suppressed the reprogramming of iPSCs (~82%). RNA-seq analysis and qRT-PCR showed that RIP3 KO MEFs expressed lower levels of genes that control cell cycle progression and cell division and higher levels of extracellular matrix-regulating genes. The growth rate of RIP3 KO MEFs was significantly slower than WT MEFs. These findings can partially explain the inhibitory effects of RIP3 deletion on iPSCs generation and show for the first time that the necroptosis kinase RIP3 plays an important role in iPSC reprogramming. In contrast to RIP3, the kinase and scaffolding functions of RIPK1 appeared to have distinct effects on reprogramming. Keywords: Reprogramming, Programmed necrosis, Necroptosis, Cell death, RIPK3, RIPK, RIP

Published
2019
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2. Mutagenesis of Glu403 to Cys in rabbit neutral endopeptidase-24.11 (neprilysin) creates a disulphide-linked homodimer: analogy with endothelin-converting enzyme

Author

V. Mien Hoang, E. Clare Sansom, and J. Anthony Turner

Subjects
Thiorphan, Protein Conformation, Protein subunit, Immunoblotting, Molecular Sequence Data, Mutant, Glutamic Acid, Endothelin-Converting Enzymes, Biochemistry, chemistry.chemical_compound, Animals, Aspartic Acid Endopeptidases, Humans, Protease Inhibitors, Amino Acid Sequence, Disulfides, Molecular Biology, Neprilysin, fungi, Phosphoramidon, Mutagenesis, Glycopeptides, Wild type, Metalloendopeptidases, Cell Biology, Enkephalin, Leucine-2-Alanine, Molecular biology, Rats, Kinetics, Directed mutagenesis, Amino Acid Substitution, chemistry, COS Cells, Mutagenesis, Site-Directed, Cystine, Rabbits, Dimerization, Oligopeptides, Research Article, Cysteine
Abstract

Neutral endopeptidase-24.11 (NEP; neprilysin; EC 3.4.24.11) and endothelin-converting enzyme (ECE) are related zinc metallopeptidases involved in the processing of biologically active peptides. Only ECE, however, exists as a disulphide-linked homodimer. The covalent linkage in rat ECE is between Cys412 in each subunit, which is equivalent to Glu403 in rabbit NEP. Here we report that directed mutagenesis of Glu403 to cysteine in rabbit NEP creates a disulphide-linked homodimer, as revealed by transient transfection in COS-1 cells and SDS/PAGE of a membrane fraction. Under reducing conditions, both the mutant (E403C) and the wild-type NEP migrate as a polypeptide of 92 kDa. However, under non-reducing conditions, the Mr of the wild type remains unchanged, whereas that of the mutant is doubled. Co-transfection of wild-type ECE and E403C NEP cDNA did not result in the production of a NEP-ECE heterodimer. Comparison of the kinetic constants for wild-type and E403C mutant NEP with either [D-Ala2,Leu5]enkephalin or 3-carboxypropanoyl-alanyl-alanyl-leucine-4-nitroanilide (Suc-Ala-Ala-Leu-NH-Np) as substrate show a decrease of approx. 50% in Vmax/Km for the mutant form. The IC50 value for inhibition of the mutant by phosphoramidon or thiorphan is increased 3-fold and 5-fold respectively. Although NEP and ECE exhibit only about 40% identity and differ substantially in substrate specificity and some other characteristics, these data indicate that they have considerable similarity in three-dimensional structure, allowing dimer formation in the mutant NEP with the disulphide link probably occurring in a hydrophilic surface loop.

Published
1997
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