Universität zu Köln

Fritsch, Melanie (2020). Caspase-8 is the molecular switch for apoptosis, necroptosis and pyroptosis. PhD thesis, Universität zu Köln.

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Abstract

The regulation of cell death is a critical step in embryonic development, tissue homeostasis and in the defence against invading pathogens. Caspase-8 (Casp8) represents the key initiator caspase inducing extrinsic apoptosis. Casp8 also inhibits necroptosis and thereby safeguard embryonic development. Here we show that Casp8 enzymatic activity is required for the inhibition of pyroptosis. In order to elucidate the specific role of Casp8 enzymatic activity we established a mouse line harbouring a point mutation in the substrate binding pocket of Casp8 (mutation of catalytic cysteine 362 to serine) which results in the lack of enzymatic activity of Casp8C362S. Expression of catalytically inactive Casp8C362S resulted in embryonic lethality at E10.5 due to cardiovascular defects similar to Casp8-/- mice. Inhibition of necroptosis via additional deletion of MLKL rescued the cardiovascular phenotype but unexpectedly caused perinatal lethality of Casp8C362S/C362S mice, indicating that loss of Casp8 enzymatic activity compromises perinatal development by additional, necroptosis-independent functions. Specific loss of Casp8 catalytic activity in intestinal epithelial cells (IECs) drives intestinal inflammation similar to Casp8IEC-KO. MLKL deficiency exacerbated the ileitis and caused prematured lethality of Casp8C362S/IEC-/Mlkl-/- mice due to induction of pyroptotic cell death associated with ASC speck formation, Casp1 activation and the maturation of pro-IL-1β. Our cell culture analyses showed that catalytically inactive Casp8 co-localises with ASC, induces ASC nucleation and Casp1 activation. Accordingly, deletion of either ASC or Casp1 prevented intestinal inflammation and premature death of Casp8C362S/C362S/Mlkl-/- mice. These results reveal a yet unknown and unexpected role for Casp8 enzymatic activity and scaffold function involving the inflammasome and pyroptosis under circumstances where apoptosis and necroptosis are blocked.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Fritsch, Melanie UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-302446
Date:	2020
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Medicine > Medizinische Mikrobiologie, Immunologie und Hygiene > Institut für Medizinische Mikrobiologie, Immunologie und Hygiene
Subjects:	Life sciences
Uncontrolled Keywords:	Keywords Language Crispr/Cas9 English Cell death English Genetics English
Date of oral exam:	14 February 2020
Referee:	Name Academic Title Kashkar, Hamid Prof. Dr. Hofmann, Kay Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/30244