To understand the mechanism of action of novel drugs targeting nitric oxide sensitive guanylyl cyclase and the physiological regulation and pharmacogenetic variation of the signal transduction pathway. Techniques range from work with purified protein to visualization in living human cells.
Nitric oxide has long been considered exclusively as a toxic air pollutant. It is now known that this gas is produced by body cells. The gaseous signaling molecule is involved in diverse functions such as cell communication in the brain, regulation of blood pressure and penile erection. The most important receptor of nitric oxide is an enzyme that produces the signaling molecule cyclic GMP. We and others have identified and localized the respective genes and have characterized the resulting enzyme isoforms.
Using a novel approach based on fluorescence resonance energy transfer from endogenous tryptophanes to the fluorescent substrate analogue MANT-GTP, we could show what conformational changes occur in the enzyme as a consequence of nitric oxide binding. In collaboration with groups in London, La Jolla and Bayer in Wuppertal, we could identify a genetic variation in susceptibility to hypoxia-induced pulmonary hypertension in high-altitude residents due to a point mutation in the enzyme. This supported guanylate cyclase as a pharmacological target for reducing pulmonary artery pressure. The recent approval of the drug riociguat to treat pulmonary hypertension has confirmed this idea. Although our data indicate a highly allosteric mechanism of action of riociguat the exact binding site is still unknown.
In contrast to nitric oxide releasing drugs further development of the allosteric modulator riociguat and the heme displacing drug cinaciguat could lead to the development of isoform specific drugs. Specific subtypes associate with specific targeting proteins within cells or are expressed in an organ specific manner. One major idea behind our research is to exploit this diversity in nitric oxide receptors for the development of novel specific drugs for single receptor subtypes with novel fields of application and a favorable side effect profile.
We have recently discovered localization of one receptor subtype to cell cell contacts and believe that drugs acting more specifically on this subtype are particularly promising.
In addition to our interest in the gasotransmitter, nitric oxide, we have also done some work on the related gasous messenger molecule carbon monoxide. This poisonous gas is produced in human cells in low concentrations during heme degradation by the enzyme heme oxygenase (HO). Two enzyme isoforms exist: inducible HO-1 and constitutive HO-2. We could show that these enzyme isoforms differ in their subcellular trafficking during hypoxia and may influence resistance to anti-leukemic drugs.
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.https://authors.elsevier.com/a/1aWX92cNmgNvTY
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