title: Regulation of Neuronal Oxygen Responses in C. elegans Is Mediated through Interactions between Globin 5 and the H-NOX Domains of Soluble Guanylate Cyclases.
abstract: Soluble guanylate cyclases (sGCs) are gas-binding proteins that control diverse physiological processes such as vasodilation, platelet aggregation, and synaptic plasticity. In the nematode Caenorhabditis elegans, a complex of sGCs, GCY-35 and GCY-36, functions in oxygen (O2) sensing. Previous studies suggested that the neuroglobin GLB-5 genetically interacts with GCY-35, and that the inhibitory effect of GLB-5 on GCY-35 function is necessary for fast recovery from prolonged hypoxia. In this study, we identified mutations in gcy-35 and gcy-36 that impact fast recovery and other phenotypes associated with GLB-5, without undermining sGC activity. These mutations, heb1 and heb3, change conserved amino acid residues in the regulatory H-NOX domains of GCY-35 and GCY-36, respectively, and appear to suppress GLB-5 activity by different mechanisms. Moreover, we observed that short exposure to 35% O2 desensitized the neurons responsible for ambient O2 sensing and that this phenomenon does not occur in heb1 animals. These observations may implicate sGCs in neuronal desensitization mechanisms far beyond the specific case of O2 sensing in nematodes. The conservation of functionally important regions of sGCs is supported by examining site-directed mutants of GCY-35, which suggested that similar regions in the H-NOX domains of O2 and NO-sensing sGCs are important for heme/gas interactions. Overall, our studies provide novel insights into sGC activity and regulation, and implicate similar structural determinants in the control of both O2 and NO sensors. Significance statement: Soluble guanylate cyclases (sGCs) control essential and diverse physiological processes, including memory processing. We used Caenorhabditis elegans to explore how a neuroglobin inhibits a complex of oxygen-sensing sGCs, identifying sGC mutants that resist inhibition. Resistance appears to arise by two different mechanisms: increased basal sGC activity or disruption of an interaction with neuroglobin. Our findings demonstrate that the inhibition of sGCs by neuroglobin is essential for rapid adaptation to either low or high oxygen levels, and that similar structural regions are key for regulating both oxygen and nitric oxide sensors. Based on our structural and functional analyses, we present the hypothesis that neuroglobin-sGC interactions may be generally important for adaptation processes, including those in organisms with more complex neurological functions.
authors.affiliation: Hebrew University of Jerusalem, Faculty of Medicine, Institute for Medical Research Israel-Canada, Jerusalem, Israel.
authors.forename: Zohar
authors.identifier: http://orcid.org/0000-0003-3115-5913
authors.initials: Z
authors.lastname: Abergel
authors.affiliation: Hebrew University of Jerusalem, Faculty of Medicine, Institute for Medical Research Israel-Canada, Jerusalem, Israel.
authors.forename: Arijit Kumar
authors.identifier: http://orcid.org/0000-0002-4687-9925
authors.initials: AK
authors.lastname: Chatterjee
authors.affiliation: Hebrew University of Jerusalem, Faculty of Medicine, Institute for Medical Research Israel-Canada, Jerusalem, Israel.
authors.forename: Binyamin
authors.initials: B
authors.lastname: Zuckerman
authors.affiliation: Hebrew University of Jerusalem, Faculty of Medicine, Institute for Medical Research Israel-Canada, Jerusalem, Israel einavg@ekmd.huji.ac.il.
authors.forename: Einav
authors.identifier: http://orcid.org/0000-0003-4050-8784
authors.initials: E
authors.lastname: Gross
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005914:Globins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006162:Guanylate Cyclase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000078787:Neuroglobin; D009474:Neurons / Q000378:metabolism*; D009569:Nitric Oxide / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D017433:Protein Structure, Secondary; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000071756:Soluble Guanylyl Cyclase
chemical_list: D029742:Caenorhabditis elegans Proteins; D009419:Nerve Tissue Proteins; D000078787:Neuroglobin; D018160:Receptors, Cytoplasmic and Nuclear; D009569:Nitric Oxide; D005914:Globins; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D010100:Oxygen
keywords: Caenorhabditis elegans; H-NOX; globin; hypoxia; oxygen-sensing; soluble guanylate cyclase