title: Characterization of tyramine β-hydroxylase, an enzyme upregulated by stress in Periplaneta americana.
abstract: Octopamine (OA) is an important neuroactive substance that modulates several physiological functions and behaviors of various invertebrate species. This biogenic monoamine, structurally related to noradrenaline, acts as a neurotransmitter, a neuromodulator, or a neurohormone in insects. The tyramine β-hydroxylase (TBH) catalyzes the last step in OA biosynthesis and thus plays a key role in the regulation of synthesis and secretion of OA in neurons. The aim of this study was to characterize TBH in the cockroach Periplaneta americana and to get a better understanding of its regulation under stress conditions in this insect. First of all, five full-length cDNAs encoding TBH isoforms were cloned from the nerve cord of the physiological model P. americana. PaTBH transcripts were found mainly expressed in nervous tissues and in octopaminergic dorsal unpaired median neurons. In addition, a new ELISA assay was developed so as to allow determination of both OA level and TBH activity in stressed cockroaches. Mechanical stressful stimulation led to a significant increase in TBH activity after 1 and 24  h, with a higher induction after 1  h than after 24  h. Thus, TBH could be considered as a promising biomarker of stress in insects rather than OA.
authors.affiliation: Laboratoire Récepteurs et Canaux Ioniques Membranaires UPRES EA 2647/USC INRA 1330, SFR QUASAV, Université d'Angers, 2 boulevard Lavoisier, F-49045 Angers Cedex, France. amelie.chatel@uco.fr
authors.forename: Amélie
authors.initials: A
authors.lastname: Châtel
authors.forename: Laurence
authors.initials: L
authors.lastname: Murillo
authors.forename: Céline Michelle
authors.initials: CM
authors.lastname: Bourdin
authors.forename: Sophie
authors.initials: S
authors.lastname: Quinchard
authors.forename: Damien
authors.initials: D
authors.lastname: Picard
authors.forename: Christian
authors.initials: C
authors.lastname: Legros
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D055162:Biocatalysis; D003001:Cloning, Molecular; D003058:Cockroaches / Q000502:physiology*; D017931:DNA Primers; D018076:DNA, Complementary; D004797:Enzyme-Linked Immunosorbent Assay; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D013312:Stress, Physiological; D015854:Up-Regulation
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D006899:Mixed Function Oxygenases; C023205:tyramine beta-hydroxylase