The characterization of a concentration-sensitive α-adrenergic-like octopamine receptor found on insect immune cells and its possible role in mediating stress hormone effects on immune function
Abstract
Octopamine (OA), the insect equivalent of norepinephrine, links the nervous system and immune system in insects. This study examines the underlying molecular mechanisms (i.e. second messenger systems) mediating OA effects on insect immune cells. At low concentrations (<1μM), OA stimulatedhemocyte spreading and phagocytosis in the larval Lepidopteran (caterpillar) Chilo suppressalis, whereas at high concentrations (>10 μM), OA inhibited hemocyte spreading and phagocytosis. Similarly, OA concentration had differential effects on two intracellular signaling pathways, Ca(2+) and cAMP. Low concentrations of OA increased intracellular Ca(2+), but only high concentrations of OA (>1 μM) led to an increase in both Ca(2+) and cAMP. We identified an α-adrenergic-like octopamine receptor in this species (CsOA1) and confirmed that it is expressed in hemocytes. After heterologous expression in HEK-293 cells, the CsOA1 receptor produced the same OA concentration-dependent responses on intracellular Ca(2+) and cAMP as had been observed in hemocytes. These findings support earlier work showing that OA has both stimulatory and suppressive effects on immune responses, depending on the OA concentration. Our evidence suggests that these biphasic ef...Continue Reading
References
Distribution and second messenger coupling of four somatostatin receptor subtypes expressed in brain
Citations
Characterization of a tyramine receptor type 2 from hemocytes of rice stem borer, Chilo suppressalis
Predator-induced stress responses in insects: A review spanning from endocrine to cellular responses
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