Laurien, Lucie Henriette (2021). The role of RIPK1 auto-phosphorylation at S166 in cell death and inflammatory signaling. PhD thesis, Universität zu Köln.
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- The role of RIPK1 auto-phosphorylation at S166 in cell death and inflammatory signaling. (deposited 06 May 2021 12:07) [Currently Displayed]
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Abstract
Receptor-Interacting Protein Kinase 1 (RIPK1) functions as a key player downstream of innate immune receptors such as Tumor necrosis factor receptor 1 (TNFR1) and Toll-like receptors(TLRs). In these signaling pathways, RIPK1 promotes cell survival and tissue homeostasis in a manner independent of its catalytic function, whereas its kinase activity mediates cell death. Importantly, RIPK1 kinase activity has emerged as a driver of cell death and inflammation in mouse models and has been implicated in the pathogenesis of human inflammatory and degenerative diseases. RIPK1 auto-phosphorylates at multiple sites, including Serine (S) 14/15, S161, S166 and Threonine (T)169 and to date, auto-phosphorylation is believed to be the main function of its kinase activity. Whereas auto-phosphorylation at S166 is routinely used as a biomarker for RIPK1 activation, its functional importance and physiological relevance have not been investigated. In this work, we aimed to shed light on the role of RIPK1 autophosphorylation at S166 for RIPK1-mediated signaling. To this aim, we generated mice expressing RIPK1 with non-phosphorylatable serine to alanine mutation at position 166 from the endogenous Ripk1 locus (Ripk1S166A/S166A mice). We show that RIPK1S166A mutation does not impair the kinase activity-independent function of RIPK1 to induce pro-inflammatory and pro-survival signaling downstream of TNFR1, TLR 3 and 4. On the other hand, we observed a partial protection from TNFR1-induced, RIPK1 kinase activity-dependent apoptosis and necroptosis as well as from TLR 3- and 4-induced necroptosis in Ripk1S166A/S166A cells, showing that RIPK1 auto-phosphorylation at S166 drives its catalytic activity-dependent function to induce cell death. Strikingly, RIPK1S166A mutation completely protected mice from RIPK1 kinase activity-dependent inflammatory pathologies in the colon, liver and skin and decreased lethality in a model of systemic inflammation, showing that in vivo, RIPK1 auto-phosphorylation at S166 is essential to drive cell death and inflammation. Mechanistically, RIPK1S166A mutation inhibited the formation of cell death-inducing complexes downstream of TNFR1 as well as TLR 3 and 4, demonstrating that auto-phosphorylation at S166 enables engagement of RIPK1 in cytotoxic complexes. Furthermore, our data suggest that RIPK1 autophosphorylation at S166 acts as a driver of kinase activity and facilitates auto-phosphorylation at other sites. Taken together, the data presented in this thesis show that auto-phosphorylation at S166 licenses RIPK1 kinase activity to induce downstream signaling and promote cell death. Therefore, our results warrant the use of S166 phosphorylation as a marker for RIPK1 activation, which can aid in the stratification of human patients that may benefit from treatment with RIPK1 kinase inhibitors.
Item Type: | Thesis (PhD thesis) | ||||||||||||
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URN: | urn:nbn:de:hbz:38-455820 | ||||||||||||
Date: | 12 April 2021 | ||||||||||||
Language: | English | ||||||||||||
Faculty: | Faculty of Mathematics and Natural Sciences | ||||||||||||
Divisions: | CECAD - Cluster of Excellence Cellular Stress Responses in Aging-Associated Diseases | ||||||||||||
Subjects: | Natural sciences and mathematics | ||||||||||||
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Date of oral exam: | 8 March 2021 | ||||||||||||
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Refereed: | Yes | ||||||||||||
URI: | http://kups.ub.uni-koeln.de/id/eprint/45582 |
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