Dokument: NRBF2, a novel component of the class III PtdIns3K complex, regulates starvation-induced autophagy and nuclear receptor-mediated gene expression

Titel:	NRBF2, a novel component of the class III PtdIns3K complex, regulates starvation-induced autophagy and nuclear receptor-mediated gene expression
URL für Lesezeichen:	https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=47976
URN (NBN):	urn:nbn:de:hbz:061-20181205-115214-6
Kollektion:	Dissertationen
Sprache:	Englisch
Dokumententyp:	Wissenschaftliche Abschlussarbeiten » Dissertation
Medientyp:	Text
Autor:	Berleth, Niklas [Autor]
Dateien:	[Dateien anzeigen] Adobe PDF [Details] 11,95 MB in einer Datei [ZIP-Datei erzeugen] Dateien vom 05.12.2018 / geändert 05.12.2018
Beitragende:	PD Dr. rer. nat. Stork, Björn [Betreuer/Doktorvater] Prof. Dr. Klein, Thomas [Gutachter]
Stichwörter:	Autophagy, NRBF2, Phosphorylation, Nuclear Receptors
Dewey Dezimal-Klassifikation:	500 Naturwissenschaften und Mathematik » 570 Biowissenschaften; Biologie
Beschreibung:	Autophagy is a lysosomal degradation pathway that maintains cellular homeostasis by removal of protein aggregates or damaged organelles. The dysregulation or selective forms of autophagy have been linked to several human maladies, encouraging research to focus on a detailed elucidation of the underlying autophagy signaling pathways. This work contributes to a better understanding of the role of the class III PtdIns3K complex during autophagy induction and its crosstalk to the other autophagy-initiating ULK1 complex. Here, nuclear receptor-binding factor 2 (NRBF2) could be identified as a novel PtdIns3K complex protein interacting with Beclin 1 (BECN1). Cellular knockout experiments using the DT40 system characterized NRBF2 as a positive regulator of the autophagic flux. The extensive crosstalk between the ULK1 complex and the PtdIns3K complex is well documented. Here, NRBF2 was identified as further target of ULK1, harboring multiple ULK1-specific phospho-acceptor sites. Identification of corresponding amino acids was achieved by mass spectrometry and was validated in intact cells. Further experiments using phospho-mimicking mutations revealed an interference of phosphorylated NRBF2 with PtdIns3K complex I assembly, which excludes ATG14 from the PtdIns3K core complex. The general autophagic capacity is not affected, whereas the specific phosphatidylinositol 3-kinase catalytic subunit type 3 (PIK3C3) activity is positively regulated by phosphorylated NRBF2 following starvation conditions. This assigns a role to NRBF2 in fine-tuning the PIK3C3 activity, possibly by priming the PtdIns3K complex I for activation upon starvation. Apart from its regulatory function during autophagy, NRBF2 comprises autophagy independent functions and is involved in the regulation of peroxisome proliferatoractivated receptor (PPAR)-dependent gene expression. NRBF2 interacts with PPAR alpha and displays a weak constitutive nuclear localization. Pharmacological activation of the PPAR isoforms alpha, beta/delta or gamma induced NRBF2-dependent upregulation of cellular ULK1 and LC3-II protein levels. Microarray experiments revealed the general involvement of NRBF2 in gene expression under growth and starvation conditions. Several transcription factors and genes related to immunological processes were identified to be regulated by NRBF2-deficiency. NRBF2-dependent gene expression following PPAR stimulation displayed only weak effects, nevertheless revealing a contrary and NRBF2-dependent regulation of Ppara itself and of its heteromeric interaction partner Rxra. Additionally, opposed effects were observed for activation of PPAR alpha and the two other PPAR family members beta/delta and gamma. In summary, NRBF2 represents a central regulator of both autophagy and PPAR-dependent gene expression.
Lizenz:	Urheberrechtsschutz
Fachbereich / Einrichtung:	Mathematisch- Naturwissenschaftliche Fakultät
Dokument erstellt am:	05.12.2018
Dateien geändert am:	05.12.2018
Promotionsantrag am:	28.08.2018
Datum der Promotion:	03.12.2018