Zierler Lab

Head of lab

Prof. Dr. rer. nat. Susanna Zierler

Group Members

Dost-Doc: Dr. Katharina Jacob; PhD Student: Max Lechner (Pharmacist); MD Students: Kilian Hölting, Marco Fraticelli (FoeFoLe)

Former Group Members

PhD Students: Wiebke Nadolni, Sarah Hampe, Elisabeth Arlt, Valentina Vettore; MS Students: Stephanie Hunger, B.Sc., Maximiliane Kronberger, B.Sc., Wiebke Nadolni, M.Sc., Jan Weber, M.Sc.; MD Students: Dorothea Lewitz (FoeFoLe), Petro Bannout Interns: Laura Fraticelli, Marco Fraticelli, Peter Stahl, Annika Schneider, B.Sc., Wiebke Nadolni, B.Sc., Jan Weber, B.Sc.; Fionán Ó Dúill, B.Sc., Tobias Klötzer, B.Sc.; Christina Moser, B.Sc., Maximiliane Kronberger, B.Sc., Moritz Pendzialek, B.Sc., Ulrike Künzel, B.Sc.; Visiting Scientist: Lynda Addington B.Sc., Dr. Eva M. Grössinger

Ion Channels in Immunity

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Our research focuses on the importance of ion channels and the regulation of nutrients such as calcium (Ca2+) and magnesium (Mg2+) in immune cells. Herein we investigate the transport of ions across cell membranes and between organelles. The aim of our research is to gain a better understanding of the importance and regulation of cation channels at the cellular level and in the context of in vivo immune reactions. This should lead to the identification of novel pharmacological targets against pro-inflammatory diseases, allergic reactions, and leukemia [1].

Fig. 1. Schematic representation of selected ion channels and transporters acting on innate and adaptive immune cells. Their contribution to healthy and dysfunctional immunity, their molecular regulators, and their expression patterns in immune cell subsets is part of our ongoing research. CFTR—cystic fibrosis transmembrane conductance regulator, CRAC—calcium release-activated channel, cyt—cytosol, DC—dendritic cell, endo—endosome, ER—endoplasmic reticulum, GABA—gamma-amino butyric acid, IP3R—inositol-3-phosphate receptor calcium channel, lum—lumen, lyso—lysosome, PM—plasma membrane, P2X—purinergic receptor, SOCE—store operated calcium entry, STIM—stromal interaction molecule, TPC— two-pore channel, TRPM—melastatin-like transient receptor potential family, V—voltage-gated, and ZIP—Zrt/lrt-like protein. Modified from [1].

Since, disruption of these pathways can result in immunodeficiencies, autoimmune diseases, allergies or cancer it is important to further understand these signaling cascades. With the acquired knowledge, we intend to uncover complex signaling pathways of immune responses and possibly find new targets for immune therapies. We will use an innovative approach combining cell- and molecular-biological, as well as electrophysiological techniques in different mouse models.

TRPM7 regulates immune homeostasis

Particularly, we are interested in the melastatin-like „transient receptor potential” (TRP) ion channel, TRPM7, and its enzymatic domain, which encodes a serine/threonine kinase. This Mg2+ and Ca2+ conducting enzyme-coupled ion channel is expressed in all eukaryotic cells and regulates fundamental cellular processes such as growth, proliferation, migration, differentiation, and survival. Knock-out of Trpm7 causes growth arrest and eventually results in cell death. Given the role of TRPM7 in cell proliferation, we were looking for pharmacological tools and experimental therapeutics for this target. Screening a marine-derived extract library, we identified and characterized a specific TRPM7 blocker, waixenicin A, isolated from a Hawaiian soft coral [2]. Chemical analogs will be tested for possible use in anti-cancer treatment.

Considering that low Mg2+ levels have been linked to memory decline, neurodegenerative diseases, decrease in muscle performance, certain cancers, and allergic reactions, it is of critical importance to further identify the mechanisms regulating the availability of this ion. Mice lacking the kinase part of this unique protein develop hypomagnesemia [3]. We demonstrated an important role of TRPM7 kinase in mast cell secretion, linking Mg2+ deficiency to allergic hypersensitivity and histamine release [4].

Our previous studies indicate a regulatory role of the TRPM7 kinase activity in the homeostasis of the immune system. Kinase-deficient mice display altered cytokine expression as well as missing intraepithelial lymphocytes (IELs) in the gut. Thus, these mice are protected from the development of an acute Graft-versus-Host Disease (GVHD) in a respective mouse model. Moreover, we demonstrated that the differentiation of pro-inflammatory Th17 cells was strongly reduced, while regulatory T cells (Tregs) developed normally in kinase-deficient animals. In vitro we could decipher the molecular mechanism behind this phenotype and identified SMAD2 as first novel native TRPM7 kinase substrate [5].

First translational results indicate that TRPM7 is also relevant for the differentiation of human T cells, as well as for the proliferation of chronic leukemia cells. TRPM7 channel and kinase, both, represent valuable potential targets for the treatment of pro-inflammatory diseases such as Multiple Sclerosis (MS) und arthritis as well as chronic leukemia. We intend to reinstate the homeostasis of the immune system using pharmacologic modulation of TRPM7. Therefore, we need to identify novel modulators for TRPM7 channel and kinase.

Intraorganellar Channels regulate Immune Cell Activity

Another arm of our research deals with so called ‘Two-Pore Channels (TPCs)’, which are intracellular cation channels. These Na+ and Ca2+ permeable ion channels play an important role in numerous (patho-)physiological and immunological processes. They are present in the bio-membrane of acidic organelles such as endosomes and lysosomes in various eukaryotic organisms. Our current research focuses on the investigation of the function of these TPCs in mast cells and basophil granulocytes. Both cell types play an important role in anaphylaxis and have a regulatory function by releasing inflammatory mediators such as histamine.

Signaling in mast cells is mainly controlled via the release of Ca2+ from the endoplasmic reticulum (ER) as well as from acidic compartments, such as endolysosomes. For the crosstalk of these organelles TPCs seem essential. We recently demonstrated an important function of the endolysosomal two-pore channel, TPC1, in regulating allergic reactions and anaphylaxis. Genetic deletion of Tpc1 resulted in accelerated anaphylaxis in vivo. The release of histamine, controlled by intracellular Ca2+ signals, was increased upon genetic or pharmacologic TPC1 inhibition. Conversely, stimulation of TPC channel activity by its endogenous ligands, nicotinic adenine dinucleotide phosphate (NAADP) or phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2), assumingly triggers the release of Ca2+ from the endolysosomes, thus improving the ER-endolysosome interactions and Ca2+ homeostasis. Consequently, TPC1 activity is a supervisory signal for mast cell exocytosis [6]. The molecular interaction between these organelles is now part of our investigations.

Literature

[1] Hoeger B & Zierler S; Ion channels and transporters in immunity - Where do we stand? Function (2023) doi: 10.1093/function/zqac070.

[2] Zierler S, Yao G, Zhang Z, Kuo C, Pörzgen P, Penner R, Horgan D, Fleig A; JBC, 286 (2011) doi: 10.1074/jbc.M111.264341.

[3] Ryazanova L V, Rondon L J, Zierler S, Hu Z, Galli J, Yamaguchi T P, Mazur A, Fleig A, Ryazanov A G; Nature Communications (2010). doi: 10.1038/ncomms1108.

[4] Zierler S, Sumoza-Toledo A, Suzuki S, Duill FO, Ryazanova LV, Penner R, Ryazanov AG, Fleig A TRPM7 kinase activity regulates murine mast cell degranulation; The Journal of Physiology (2016) doi: 10.1113/JP271564.

[5] Romagnani A, Vettore V, Rezzonico-Jost T, Hampe S, Rottoli E, Nadolni W, Perotti M, Meier MA, Hermanns C, Geiger S, Wennemuth G, Recordati C, Matsushita M, Muehlich S, Proietti M, Chubanov V, Gudermann T, Grassi F, Zierler S; TRPM7 kinase activity is essential for T cell colonization and alloreactivity in the gut. Nature Communications (2017) doi: 10.1038/s41467-017-01960-z.

[6] Arlt E, Fraticelli M, Tsvilovskyy V, Nadolni W, Breit A, O’Neill TJ, Resenberger S, Wennemuth G, Wahl-Schott C, Biel M, Grimm C, Freichel M, Gudermann T, Klugbauer N, Boekhoff I, Zierler S TPC1 deficiency or blockade augments systemic anaphylaxis and mast cell activity. Proc Natl Acad Sci U S A. (2020) doi: 10.1073/pnas.1920122117.

Funding:

Current Projects

2022 – 2026 DFG CRC/TRR-152 (3) P14; TR(I)Ps to Homeostasis; The kinase-coupled TRPM7-channel as regulator of immune system homeostasis

2022 – 2024 FöFoLe, LMU (Marco Fraticelli), Pharmakologische Modulation des TRPM7 Kanals mit Hilfe eines Naturstoffes

Finished Projects

2018 – 2022 DFG CRC/TRR-152 (2) P14; TR(I)Ps to Homeostasis; The kinase-coupled TRPM7-channel as regulator of immune system homeostasis

2018 – 2020 FöFoLe, LMU (Kilian Hölting), TRPM7-Kanal und -Kinase vermittelte Signalkaskaden - von der Membran zum Kern

2014 – 2018 DFG CRC/TRR-152 (1) P14; TR(I)Ps to Homeostasis; The kinase-coupled TRPM7-channel as regulator of immune system homeostasis

2012 – 2016 Marie Curie Stiftung, FP7-PEOPLE-20112-CIG no. 322 185, REA, Brüssel, Role of enzyme-coupled TRP channels in immune cells

2012 – 2014 ERA.Net RUS, FPY ERA, FP7, STProjets-184, BMBF, Bonn, TRPM7 in regulation of T cell subsets and purinergic signaling

03/2012 FöFoLe, LMU (Dorothea Lewitz), Rolle von enzymgekoppelten Ionenkanälen bei der Aktivierung und Differenzierun