Neue Therapieoption für akute hepatische Porphyrien

Was ist neu? Therapie mit Givosiran Givosiran ist ein kleines synthetisches doppelsträngiges siRNA-Fragment mit 20 Basenpaaren Länge. Eine prospektive, randomisierte multizentrische Studie (Envision) zeigte erstmalig die klinische Wirksamkeit von monatlich subkutan applizierten synthetischen RNA-Molekülen („small interfering“ RNA, siRNA) zur Prävention von Attacken bei akuten hepatischen Porphyrien (AHP) 2. Die Koppelung von siRNA-Molekülen an N-Acetyl-Galaktosamin (GalNAc) und die hierdurch leberspezifische Aufnahme durch den Asialoglykoprotein-Rezeptor auf Hepatozyten sind ein Meilenstein in der Hepatologie. Dies führt zu einer hochselektiven Inhibition der Translation der bei AHP überexprimierten hepatischen Aminolävulinsäure-Synthase (ALAS1). Givosiran wurde in den USA und in Europa zur Behandlung akuter hepatischer Porphyrien zugelassen. Fazit Der Erfolg dieser innovativen Therapie eröffnet die Möglichkeit, prinzipiell jeden Prozess auf der Ebene der hepatozytären mRNA-Translation zu hemmen. Der therapeutische Effekt der stabilisierten siRNA hält über Wochen an. Die Behandlung mit Givosiran ist aktuell jedoch sehr kostenintensiv. Aufgrund von bislang unverstandenen Veränderungen der Nierenfunktion und Aminotransferasen ist im ersten halben Jahr zudem eine monatliche Überwachung nötig.

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Apoptosis and Autophagy Induction in Mammalian Cells by Small Interfering RNA Knockdown of mRNA Capping Enzymes

Molecular and Cellular Biology ◽

10.1128/mcb.00021-08 ◽

2008 ◽

Vol 28 (19) ◽

pp. 5829-5836 ◽

Cited By ~ 22

Author(s):

Chun Chu ◽

Aaron J. Shatkin

Keyword(s):

Rna Polymerase ◽

Rna Polymerase Ii ◽

Mammalian Cells ◽

Small Interfering Rna ◽

Fluorescent Protein ◽

Mrna Translation ◽

Proteolytic Processing ◽

Tunel Staining ◽

Interfering Rna ◽

Capping Enzymes

ABSTRACT Addition of a 5′ cap to RNA polymerase II transcripts, the first step of pre-mRNA processing in eukaryotes from yeasts to mammals, is catalyzed by the sequential action of RNA triphosphatase, guanylyltransferase, and (guanine-N-7)methyltransferase. The effects of knockdown of these capping enzymes in mammalian cells were investigated using T7 RNA polymerase-synthesized small interfering RNA and also a lentivirus-based inducible, short hairpin RNA system. Decreasing either guanylyltransferase or methyltransferase resulted in caspase-3 activation and elevated terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) staining characteristic of apoptosis. Induction of apoptosis was independent of p53 tumor suppressor but dependent on BAK or BAX. In addition, levels of the BH3 family member Bim increased, while Mcl-1 and Bik levels remained unchanged during apoptosis. In contrast to capping enzyme knockdown, apoptosis induced by cycloheximide inhibition of protein synthesis required BAK but not BAX. Both Bim and Mcl-1 levels decreased in cycloheximide-induced apoptosis while Bik levels were unchanged, suggesting that apoptosis in siRNA-treated cells is not a direct consequence of loss of mRNA translation. siRNA-treated BAK−/− BAX−/− double-knockout mouse embryonic fibroblasts failed to activate capase-3 or increase TUNEL staining but instead exhibited autophagy, as demonstrated by proteolytic processing of microtubule-associated protein 1 light chain 3 (LC3) and translocation of transfected green fluorescent protein-LC3 from the nucleus to punctate cytoplasmic structures.

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Localization of Double-stranded Small Interfering RNA to Cytoplasmic Processing Bodies Is Ago2 Dependent and Results in Up-Regulation of GW182 and Argonaute-2

Molecular Biology of the Cell ◽

10.1091/mbc.e08-08-0796 ◽

2009 ◽

Vol 20 (1) ◽

pp. 521-529 ◽

Cited By ~ 48

Author(s):

Aarti Jagannath ◽

Matthew J.A. Wood

Keyword(s):

Small Interfering Rna ◽

Protein Complexes ◽

Resonance Energy Transfer ◽

Resonance Energy ◽

Mrna Translation ◽

Processing Bodies ◽

P Bodies ◽

Argonaute 2 ◽

Body Component ◽

Interfering Rna

Processing bodies (P-bodies) are cytoplasmic foci implicated in the regulation of mRNA translation, storage, and degradation. Key effectors of microRNA (miRNA)-mediated RNA interference (RNAi), such as Argonaute-2 (Ago2), miRNAs, and their cognate mRNAs, are localized to these structures; however, the precise role that P-bodies and their component proteins play in small interfering RNA (siRNA)-mediated RNAi remains unclear. Here, we investigate the relationship between siRNA-mediated RNAi, RNAi machinery proteins, and P-bodies. We show that upon transfection into cells, siRNAs rapidly localize to P-bodies in their native double-stranded conformation, as indicated by fluorescence resonance energy transfer imaging and that Ago2 is at least in part responsible for this siRNA localization pattern, indicating RISC involvement. Furthermore, siRNA transfection induces up-regulated expression of both GW182, a key P-body component, and Ago2, indicating that P-body localization and interaction with GW182 and Ago2 are important in siRNA-mediated RNAi. By virtue of being centers where these proteins and siRNAs aggregate, we propose that the P-body microenvironment, whether as microscopically visible foci or submicroscopic protein complexes, facilitates siRNA processing and siRNA-mediated silencing through the action of its component proteins.

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