Characterization of serotonin receptors Aj5-HTR2 and Aj5-HTR7 reveals potential roles in circadian regulation of Apostichopus japonicus

  • Gen Comp Endocrinol. 2026 Mar:379:114913. doi: 10.1016/j.ygcen.2026.114913.
Yibo Wang  1 ,  Yuting Liu  1 ,  Zhiqing Ye  1 ,  Lifei Ge  1 ,  Guanyu Han  1 ,  Jingjing Jiang  1 ,  Yuqian Chen  1 ,  Jixiu Wang  1 ,  Jieyang Weng  1 ,  Jingwen Yang  2 ,  Tianming Wang  3
Affiliations
  • 1. National Engineering Laboratory of Marine Germplasm Resources Exploration and Utilization, Marine Science and Technology College, Zhejiang Ocean University, Zhoushan, Zhejiang 316022, People's Republic of China.
  • 2. National Engineering Laboratory of Marine Germplasm Resources Exploration and Utilization, Marine Science and Technology College, Zhejiang Ocean University, Zhoushan, Zhejiang 316022, People's Republic of China. Electronic address: [email protected].
  • 3. National Engineering Laboratory of Marine Germplasm Resources Exploration and Utilization, Marine Science and Technology College, Zhejiang Ocean University, Zhoushan, Zhejiang 316022, People's Republic of China. Electronic address: [email protected].
PMID: 41819218 DOI: 10.1016/j.ygcen.2026.114913
Abstract

Serotonin (5-hydroxytryptamine, 5-HT) is an evolutionarily conserved neurotransmitter that mediates neuroendocrine signaling through 5-hydroxytryptamine receptors (5-HTRs). In this study, two 5-HT Receptor subtypes, Aj5-HTR2 and Aj5-HTR7, were cloned and functionally characterized from the sea cucumber Apostichopus japonicus. Functional assays demonstrated that both receptors are signaling-competent molecules, exhibiting rapid receptor internalization upon 5-HT stimulation, along with dose-dependent increases in intracellular CA2+ or cyclic adenosine monophosphate (cAMP) levels and ERK1/2 phosphorylation. Quantitative Real-Time PCR showed that Aj5-HTR2 was highly expressed in the nerve ring and tentacles, whereas Aj5-HTR7 was highly expressed in the Polian vesicle and muscle. Moreover, both receptors exhibited distinct day-night expression rhythms, suggesting subtype-specific involvement in circadian neuroendocrine regulation. In summary, this work expands the repertoire of 5-HTRs in sea cucumbers and provides new insights into their potential roles in circadian neuroendocrine regulation.

Keywords
Apostichopus japonicus; Circadian rhythm; G protein-coupled receptor; Neuroendocrine regulation; Serotonin receptor.
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