title: Serotonin modulates insect hemocyte phagocytosis via two different serotonin receptors.
abstract: Serotonin (5-HT) modulates both neural and immune responses in vertebrates, but its role in insect immunity remains uncertain. We report that hemocytes in the caterpillar, Pieris rapae are able to synthesize 5-HT following activation by lipopolysaccharide. The inhibition of a serotonin-generating enzyme with either pharmacological blockade or RNAi knock-down impaired hemocyte phagocytosis. Biochemical and functional experiments showed that naive hemocytes primarily express 5-HT1B and 5-HT2B receptors. The blockade of 5-HT1B significantly reduced phagocytic ability; however, the blockade of 5-HT2B increased hemocyte phagocytosis. The 5-HT1B-null Drosophila melanogaster mutants showed higher mortality than controls when infected with bacteria, due to their decreased phagocytotic ability. Flies expressing 5-HT1B or 5-HT2B RNAi in hemocytes also showed similar sensitivity to infection. Combined, these data demonstrate that 5-HT mediates hemocyte phagocytosis through 5-HT1B and 5-HT2B receptors and serotonergic signaling performs critical modulatory functions in immune systems of animals separated by 500 million years of evolution.
authors.affiliation: State Key Laboratory of Rice Biology, Institute of Insect Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Yi-Xiang
authors.initials: YX
authors.lastname: Qi
authors.affiliation: State Key Laboratory of Rice Biology, Institute of Insect Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Rice Biology, Institute of Insect Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Meng-Qi
authors.initials: MQ
authors.lastname: Li
authors.affiliation: State Key Laboratory of Rice Biology, Institute of Insect Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Ya-Su
authors.initials: YS
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Rice Biology, Institute of Insect Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Ren-Ying
authors.initials: RY
authors.lastname: Xia
authors.affiliation: State Key Laboratory of Rice Biology, Institute of Insect Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Gong-Yin
authors.initials: GY
authors.lastname: Ye
mesh_terms: D000818:Animals; D002080:Butterflies; D004331:Drosophila melanogaster; D006434:Hemocytes / Q000187:drug effects* / Q000502:physiology*; D010587:Phagocytosis / Q000187:drug effects*; D011985:Receptors, Serotonin / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism*
chemical_list: D011985:Receptors, Serotonin; D012701:Serotonin
keywords: D. melanogaster; bacteria infection; hemocyte; immunology; infectious disease; innate immunity; microbiology; phagocytosis; serotonin receptor