Our group focuses on unraveling how novel drugs interact with nitric oxide‐sensitive guanylyl cyclase and on characterizing the physiological regulation and pharmacogenetic variations of this signal transduction pathway. Our research employs a wide array of techniques—from studying purified proteins in vitro to visualizing their behavior in living human cells—to gain comprehensive insights into these processes. We are collaborating closely with Peter Sandner (Bayer, Wuppertal) and Alban Ziegler (Toulouse).
Drug research and development programmes targeting soluble guanylyl cyclase (sGC) have been highly successful, leading to the launch of the sGC stimulators riociguat for pulmonary hypertension (2014) and vericiguat for chronic heart failure (2021). As the main receptor for nitric oxide, sGC plays a vital role in various physiological processes. It consists of an alpha and a beta subunit, with two distinct isoforms identified in humans: GC-1 (α1/β1) and GC-2 (α2/β1). Growing evidence indicates that these isoforms engage in different downstream signalling pathways, indicating that isoform-specific approaches could lead to novel therapeutic opportunities and reduce potential side effects.
Histidine 105 in the heme binding pocket of the β1 subunit of sGC is a crucial residue for heme binding and natural enzyme activation by nitric oxide. We have recently shown that the second generation sGC activators runcaciguat activates heme-free sGC only when the β1 Histidine 105 residue is present. In this respect, runcaciguat is similar to the natural ligand nitric oxide. In contrast, the first generation sGC activator cinaciguat activates sGC independent of β1 Histidine 105 .
Very recently, we have discovered runcaciguat as the first isoform specific sGC activator. This selective targeting could explain the favourable clinical effect of runcaciguat in chronic kidney disease.
Alban Ziegler identified a de novo heterozygous variant c.1458G>T p.(E486D) in the gene encoding the sGC α2 subunit. We evaluated the effect of the corresponding enzyme variant α2E486D/β1 using concentration-response measurements in cytosolic fractions of HEK293 cells, UV-vis absorbance spectra of the corresponding purified enzymes, and examination of overexpressed fluorescent protein-tagged constructs by confocal laser scanning microscopy.
The patient presented with precocious peripheral puberty that mirrors the autonomous ovarian puberty observed in McCune-Albright syndrome, along with severe intellectual disability. In vitro assays revealed that the mutant GC-2 enzyme exhibits increased affinity for nitric oxide. This suggests that chronic hyperactivation of GC-2 can have detrimental effects, highlighting the benefits of runcaciguat's selective activation of GC-1.
Stomberg, S., Rühle, A., Wittrien, T., Sandner, P., Behrends, S. (2025) Discovery of the first isoform-specific sGC activator: selective activation of GC-1 by runcaciguat. Eur J Pharmacol Mar 25:177557.
https://doi.org/10.1016/j.ejphar.2025.177557
Wittrien, T., Rühle, A., Elgert, C., Mathar, I., Sandner, P., Behrends, S. (2025) Runcaciguat activates soluble guanylyl cyclase via the histidine essential for heme binding and nitric oxide activation. Biochem Pharmacol. 232:116739.
https://doi.org/10.1016/j.bcp.2025.116739
Wittrien, T., Ziegler, A., Rühle, A., Stomberg, S., Meyer, R., Bonneau, D., Rodien, P., Prunier-Mirebeau, D., Coutant, R., Behrends, S. (2024) Heterozygous gain of function variant in GUCY1A2 may cause autonomous ovarian hyperfunction. Eur J Endocrinol. 190(4):266-274
Kintos, D.P., Salagiannis, K., Vazoura, V., Wittrien, T., Papakyriakou, A., Nikolaropoulos, S.S., Behrends, S., Topouzis, S., Fousteris, M.A. (2022) Design, synthesis and biological evaluation of new 3,4-dihydroquinoxalin-2(1 H)-one derivatives as soluble guanylyl cyclase (sGC) activators. Heliyon 8(11):e11438.
https://doi.org/10.1016/j.heliyon.2022.e11438
Elgert, C., Rühle, A., Sandner, P., Behrends, S. (2020) Thermal shift assay: Strengths and weaknesses of the method to investigate the ligand-induced thermostabilization of soluble guanylyl cyclase. J Pharm Biomed Anal. 181:113065.
Elgert, C., Rühle, A, Sandner, P., Behrends, S. (2019) A novel soluble guanylyl cyclase activator, BR 11257, acts as a non-stabilising partial agonist of sGC. Biochem Pharmacol. 163:142-153.
Sömmer, A., Behrends, S. (2018) Methods to investigate structure and activation dynamics of GC-1/GC-2. Nitric Oxide 78:127-139
Sömmer, A., Behrends, S. (2018) Synergistic stabilisation of NOsGC by cinaciguat and non-hydrolysable nucleotides: Evidence for sGC activator-induced communication between the heme-binding and catalytic domains. Biochim Biophys Acta 1866:702-711.
Sömmer, A., Sandner, P., Behrends, S. (2018) BAY 60-2770 activates two isoforms of nitric oxide sensitive guanylyl cyclase: Evidence for stable insertion of activator drugs. Biochem Pharmacol. 147:10-20.
Schäfer, B., Moriishi, K. ,Behrends, S.(2017) Insights into the mechanism of isoenzyme-specific signal peptide peptidase-mediated translocation of heme oxygenase. PlosOne 12: e0188344, 1-20.
Schäfer, B., Behrends, S. (2017) Translocation of heme oxygenase-1 contributes to imatinib resistance in chronic myelogenous leukemia. Oncotarget 8:67406-67421.
Hochheiser, J., Haase, T., Busker, M., Sömmer, A., Kreienkamp, HJ., Behrends, S. (2016) Heterodimerization with the β1 subunit directs the α2 subunit of nitric oxide-sensitive guanylyl cyclase to calcium-insensitive cell-cell contacts in HEK293 cells: Interaction with Lin7a. Biochem Pharmacol. 122: 23-32.
Busker, M., Neidhardt, I., Behrends, S. (2014). Nitric oxide activation of guanylate cyclase pushes the α1 signaling helix and the β1 heme-binding domain closer to the substrate-binding site. J Biol Chem. 289:476-484.
Wilkins, M.R., Aldashev, A.A., Wharton, J., Rhodes, C.J.; Vandrovcova, J., Kasperaviciute, D., Bhosle, S.G., Mueller, M., Geschka, S., Rison, S., Kojonazarov, B., Morrell, N.W., Neidhardt, I., Surmeli, B, Aitman, T.J., Stasch, J.-P., Behrends, S., Marletta, M.A. (2014). The α1-A680T variant in GUCY1A3 as a candidate conferring protection from pulmonary hypertension among Kyrgyz highlanders. Circ Cardiovasc Genet 7:920-929.
Linnenbaum M, Busker M, Kraehling JR, Behrends S. (2012). Heme oxygenase isoforms differ in their subcellular trafficking during hypoxia and are differentially modulated by cytochrome P450 reductase. PlosOne 7: e35483, 1-11.
Kraehling, J.R., Busker, M., Haase, T., Haase, N., Koglin, M., Linnenbaum, M., Behrends, S. (2011). The amino-terminus of nitric oxide sensitive guanylyl cyclase α1 does not affect dimerization but influences subcellular localization. PlosOne 6:e25772, 1-11.
Haase, N., Haase, T., Seeanner, M., Behrends, S. (2010). Nitric oxide sensitive guanylyl cyclase activity decreases during cerebral postnatal development because of a reduction in heterodimerization. J Neurochem. 112:542-51.
Haase, N., Haase, T., Kraehling, J.R., Behrends, S. (2010). Direct fusion of subunits of heterodimeric nitric oxide sensitive guanylyl cyclase leads to functional enzymes with preserved biochemical properties: Evidence for isoform specific activation by ciguates. Biochem Pharmacol. 80:1676-83.
Haase, T., Haase, N., Krähling, J., Behrends, S. (2010). Fluorescent Fusion Proteins of Soluble Guanylyl Cyclase Indicate Proximity of the Heme Nitric Oxide Domain and Catalytic Domain. PlosOne 5:e11617, 1-10.
Professor of Pharmacology, Institute of Pharmacology, University of Braunschweig
Associate professor, University of Toronto
Canada Research Chair for Molecular Pharmacology
Group leader and habilitation, University clinic Hamburg Eppendorf
Postdoctoral Fellow, Institute of Pharmacology, Free University Berlin
Dr. med. at Institute of Pharmacology, University of Göttingen
Study of medicine, Universities Göttingen, Würzburg and Hannover