Center for Molecular Medicine Cologne

Hamid Kashkar - B 04

Role of caspase-8 in B cell development and lymphomagenesis

Introduction

Casp8 is involved in pathogenesis of different human diseases including lymphatic disorders and recent research efforts have successfully evaluated its therapeutic potential (Emricasan in phase II-III clinical trials).

By using novel transgenic mice mimicking the therapeutic inhibition of Casp8 enzymatic activity this project will provide substantial knowledge about the role of Casp8 in lymphocyte homeostasis and its therapeutic potential in B cell lymphoma.

Extrinsic apoptosis is a central regulatory mechanism of the B cell compartment and its dysfunction causes B cell diseases such as autoimmunity and lymphoma. Caspase-8 (Casp8) is the initiator caspase of the extrinsic apoptotic pathway and was initially described to induce this non-lytic programmed cell death (apoptosis). Casp8 was further characterized as the key inhibitor of necroptosis (lytic regulated cell death) and was shown to be indispensible for embryonic development.

Recently, we discovered an additional function of Casp8 demonstrating that enzymatic inactive Casp8 acts as a scaffold and induces pyroptosis (lytic inflammatory regulated cell death) and inflammation. Our studies explored Casp8 as a central molecular switch controlling apoptosis, necroptosis and pyroptosis. Based on this striking observation, we aim to investigate the role of Casp8 scaffold function versus its enzymatic activity in B cell homeostasis.

Our Aims

  1. B cell-specific roles of Casp8. Here we will specifically delete Casp8 or express inactive Casp8C362S specifically in B cells and will study B cell development in mouse.
  2. Role of Casp8 in pathogenesis of chronic lymphocytic leukemia (CLL). Here we will use CLL mouse model and delete Casp8 or express inactive Casp8C362S specifically in B cells and will study CLL development/progression in mice.

Previous Work

In order to investigate the physiologic role of Casp8 enzymatic activity we recently generated a knock-in mouse line (using CRISPR/Cas9 gene-editing) expressing enzymatically inactive Casp8C362S Fritsch et al., Nature 2019). Similar to Casp8-/-, lack of Casp8 enzymatic activity caused lethality in Casp8C362S/C362S embryos.

Our data revealed that the inhibition of necroptosis by MLKL deletion (Mlkl-/-) rescued the embryonic development in Casp8-/- mice but unexpectedly failed to prevent embryonic lethality of Casp8C362S/C362S mice, indicating that the expression of enzymatically inactive Casp8C362S causes necroptosis-independent death during embryonic development. Further extensive analysis using tissue-specific expression of Casp8C362S discovered a novel function for Casp8 demonstrating that enzymatically inactive Casp8C362S acts as a scaffold and induces pyroptosis.

We could show that Casp8C362S induces the nucleation of the inflammasome adaptor ASC, promotes the activation of the inflammatory caspase-1 (Casp1) and results in pyroptosis as well as secretion of inflammatory cytokines IL-1β and IL-18. Accordingly, only the combined deletion of MLKL together with ASC (Casp8C362S/C362S/Mlkl-/-/Asc-/-) or Casp1 (Casp8C362S/C362S/Mlkl-/-/Casp1-/-) rescued embryonic lethality of Casp8C362S/C362S mice.

Our studies explored a novel role of Casp8 in cellular death and inflammatory cascades and represent Casp8 as a central molecular switch controlling apoptosis, necroptosis and pyroptosis (Fritsch et al., Nature 2019).

Project Related publications

  1. Pallasch CP, Schulz A, Kutsch N, Schwamb J, Hagist S, Kashkar H, Ultsch A, Wickenhauser C, Hallek M, Wendtner CM. Overexpression of TOSO in CLL is triggered by B-Cell receptor signaling and associated with progressive disease. Blood 2008, 112:4213-9
  2. Frenzel LP, Patz m, Pallasch CP, Brinker R, Claasen J, Schulz A, Hallek M, Kashkar H*, and Wendtner CM*. Novel X-linked inhibitor of apoptosis inhibiting compound as sensitizer for TRAIL-mediated apoptosis in chronic lymphocytic leukaemia with poor prognosis. Br J Haematol. 2011, 152(2):191-200. *equal contribution
  3. Huelsemann MF, Patz M, Beckmann L, Brinkmann K, Otto T, Fandrey J, Becker HJ, Theurich S, von Bergwelt-Baildon M, Pallasch CP, Zahedi RP, Kashkar H, Reinhardt HC, Hallek M, Wendtner CM, Frenzel LP. Hypoxia-induced p38 MAPK activation reduces Mcl-1 expression and facilitates sensitivity towards BH3 mimetics in chronic lymphocytic leukemia. Leukemia 2015, 29:981-4
  4. Knittel G*, Liedgens P*, Korovkina D*, Seeger JM*, Al-Baldawi Y, Al-Maarri M, Fritz C, Vlantis K, Bezhanova S, Scheel AH, Wolz OO, Reimann M, Möller P, López C, Schlesner M, Lohneis P, Weber AN, Trümper L, Consortium IM, Staudt LM, Ortmann M, Pasparakis M, Siebert R, Schmitt CA, Klatt AR, Wunderlich FT, Schäfer SC, Persigehl T, Montesinos-Rongen M, Odenthal M, Büttner R, Frenzel LP§Kashkar H§, Reinhardt HC§. (2016) B cell-specific conditional expression of Myd88p.L252P leads to the development of diffuse large B cell lymphoma in mice. Blood 2016, 127(22):2732-41. * and§ equal contribution
  5. Chauhan D*, Bartok E*, Gaidt MM, Bock FJ, Herrmann J, Seeger JM, Broz P, Beckmann R, Kashkar H, Tait SWG, Müller R, Hornung V. BAX/BAK induced apoptosis results in caspase-8 dependent IL-1b maturation in primary macrophages Cell Rep. 2018, 25(9):2354-2368
  6. Fritsch M, Günther SD, Schwarzer R, Albert MC, Schorn F, Werthenbach JP, Schiffmann LM, Stair N, Stocks H, Seeger JM, Lamkanfi M, Krönke M, Pasparakis M, Kashkar H. Caspase-8 is the molecular switch for apoptosis, necroptosis and pyroptosis. Nature 575:683-687
Prof. Dr. Hamid Kashkar CMMC Cologne
Prof. Dr. Hamid Kashkar

Inst. for Med. Microbiology, Immunology and Hygiene (IMMIH) - / RG location - CECAD Building

Principal Investigator - B 04

+49 221 478 84091

+49 221 478 32002

Inst. for Med. Microbiology, Immunology and Hygiene (IMMIH) - / RG location - CECAD Building

Goldenfelsstraße 19-21

50935 Cologne

http://immih.uk-koeln.de/forschung/ag-kashkar

CMMC Profile Page

Curriculum Vitae (CV)

Publications on PubMed

Publications - Hamid Kashkar

Link to PubMed

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