Regulation of Autophagy and Apoptosis in B lymphocytes

• Applicant: Professor Dr. Björn Stork
• Subject Area: Immunology
• Term: from 2013 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 234605336

• Final Report Year: 2017

Final Report Abstract

Lymphocytes form the basis for adaptive immune responses. Adaptive or acquired immune responses are essential for the specific recognition of pathogens and provide protective immunity against reinfections. The central objective of this proposal was the in-depth analysis of autophagic and apoptotic pathways in B lymphocytes. Both autophagy and apoptosis are central cellular stress responses and accordingly critically influence the B cell compartment. Furthermore, we aimed at investigating the cross-talk between these two cellular stress responses in B lymphocytes and at optimizing therapies targeting B cell-specific malignancies. With regard to autophagy, we observed significant alterations of B cell antigen receptor (BCR)-induced signaling in cells deficient for Beclin 1. Beclin 1 is a component of the autophagy-inducing class III PtdIns3K complex. We initially tried to identify novel Beclin 1-interacting proteins. Among these, we found nuclear receptor binding factor 2 (NRBF2). We observed that NRBF2 positively regulates starvation-induced autophagy and that NRBF2 is a substrate of the autophagy-activating protein kinase ULK1. Since NRBF2 was originally identified as interaction partner of nuclear receptors of the peroxisome proliferator-activated receptor (PPAR) family, we speculate that NRBF2 regulates autophagy not only at the short-term level by regulating class III PtdIns3K complex activity, but potentially also at the long-term level by regulating the transcriptional control of autophagy. One central aim of this proposal was to investigate the cellular effects of monoclonal anti-CD20 antibodies. At present, several B cell associated pathologies are treated with monoclonal anti-CD20 antibodies. Different modes of action have been suggested for these antibodies, such as antibodydependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), or direct induction of apoptosis. According to our data, direct induction of cell death is not a major mode of action of anti- CD20 antibodies. Furthermore, we did not observe significant induction of autophagy upon anti-CD20 treatment. Finally, we have identified several mutations in the ULK1 gene of patients suffering from a relapse of acute lymphoblastic leukemia (ALL). The finding that these mutations were detected only at relapse suggests that autophagy in general or ULK1 in particular are relevant at this stage for drug resistance and survival of ALL cells. Currently, we are investigating the functional relevance of these ULK1 mutations with regard to the responsiveness of ALL cells to chemotherapeutics. Collectively, in this project we were able to identify an additional component of the autophagy-inducing class III PtdIns3K complex and mutations in the ULK1 gene occurring during the relapse of ALL. Future studies will have to reveal whether these findings can be exploited for the therapy of B cell malignancies.

Publications

• (2018) Systematic analysis of ATG13 domain requirements for autophagy induction. Autophagy 14 (5) 743–763
  Wallot-Hieke, Nora; Verma, Neha; Schlütermann, David; Berleth, Niklas; Deitersen, Jana; Böhler, Philip; Stuhldreier, Fabian; Wu, Wenxian; Seggewiß, Sabine; Peter, Christoph; Gohlke, Holger; Mizushima, Noboru; Stork, Björn
  
• (2018) Targeting urothelial carcinoma cells by combining cisplatin with a specific inhibitor of the autophagy-inducing class III PtdIns3K complex. Urologic oncology 36 (4) 160.e1–160.e13
  Schlütermann, David; Skowron, Margaretha A.; Berleth, Niklas; Böhler, Philip; Deitersen, Jana; Stuhldreier, Fabian; Wallot-Hieke, Nora; Wu, Wenxian; Peter, Christoph; Hoffmann, Michèle J.; Niegisch, Günter; Stork, Björn
  
• ATG13: Just a companion, or an executor of the autophagic program? Autophagy 2014;10:944‐956
  Alers S, Wesselborg S, Stork B
  
• Autophagy signal transduction by ATG proteins: from hierarchies to networks. Cell Mol Life Sci 2015;72:4721‐4757
  Wesselborg S, Stork B
  
• Deubiquitinase inhibition by WP1130 leads to ULK1 aggregation and blockade of autophagy. Autophagy 2015;11:1458‐1470
  Drießen S, Berleth N, Friesen O, Löffler AS, Böhler P, Hieke N, Stuhldreier F, Peter C, Schink KO, Schultz SW, Stenmark H, Holland P, Simonsen A, Wesselborg S, Stork B
  
• Expression of an ULK1/2 binding‐deficient ATG13 variant can partially restore autophagic activity in ATG13‐deficient cells. Autophagy 2015;11:1471‐1483
  Hieke N, Löffler AS, Kaizuka T, Berleth N, Böhler P, Drießen S, Stuhldreier F, Friesen O, Assani K, Schmitz K, Peter C, Diedrich B, Dengjel J, Holland P, Simonsen A, Wesselborg S, Mizushima N, Stork B
  
• A systems study reveals concurrent activation of AMPK and mTOR by amino acids. Nat Commun 2016;7:13254
  Dalle Pezze P, Ruf S, Sonntag AG, Langelaar‐Makkinje M, Hall P, Heberle AM, Razquin Navas P, van Eunen K, Tölle RC, Schwarz JJ, Wiese H, Warscheid B, Deitersen J, Stork B, Fäßler E, Schäuble S, Hahn U, Horvatovich P, Shanley DP, Thedieck K
  
• Study of ULK1 Catalytic Activity and Its Regulation. Methods Enzymol 2017;587:391‐404
  Stork B, Dengjel J