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Putative regulatory mechanism of prothoracicotropic hormone (PTTH) secretion in the American cockroach, Periplaneta americana as inferred from co-localization of Rab8, PTTH, and protein kinase C in neurosecretory cells


Small GTPases of the Rab family act as essential regulators of vesicle transport pathways, including the exocytosis of neurohormones. These processes are not well-understood in insects. To address the physiological function of Rab proteins and their phosphorylation in insect neurosecretion, Rab8-like, prothoracicotropic hormone (PTTH)-like, and protein kinase C (PKC)-like immunohistochemical reactivities (-ir) were investigated in the brain of the American cockroach, Periplaneta americana. All the antibodies tested reacted with neurons in the pars intercerebralis, corpora cardiaca, and nervi corporis allati I. Double-labeling experiments demonstrated that all PTTH-ir were colocalized with Rab8-ir and PKC-ir in the pars intercerebralis, although exclusive reactivity was present to antisera against Rab8 or PKC. These findings support the notion that Rab8-like antigen is phosphorylated by PKC, and that this phosphorylation is involved in the axonal transport and secretion of PTTH in this species.

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We thank Dr. I. Sauman for providing the anti-PTTH antibody. We also thank Dr. M. Takagi who helped us with the production of the anti-Rab8 antibody.

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Correspondence to Makio Takeda.

Additional information

This work was supported by a Grant-in-Aid for Scientific Research (B) 1838043, (C) 20580053, and Global Center of Education and Research Program (19GCOE01) from the Japan Society for the Promotion of Science.

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Hiragaki, S., Uno, T. & Takeda, M. Putative regulatory mechanism of prothoracicotropic hormone (PTTH) secretion in the American cockroach, Periplaneta americana as inferred from co-localization of Rab8, PTTH, and protein kinase C in neurosecretory cells. Cell Tissue Res 335, 607–615 (2009).

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  • Rab protein
  • Neurosecretion
  • Protein kinase C
  • Prothoracicotropic hormone
  • Periplaneta americana (Insecta)