ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2019) 63 GP244 | DOI: 10.1530/endoabs.63.GP244

Tomosyn negatively regulates arginine vasopressin secretion in embryonic stem cell-derived neurons

Yoshihisa Sugimura1, Seiji Takeuchi2, Takashi Watanabe3, Atsushi Kiyota4, Haruki Fujisawa1, Yusuke Seino1 & Atsushi Suzuki1

1Department of Endocrinology and Metabolism, Fujita Health University, Toyoake, Japan; 2Sakai Naika Medical Clinic, Handa, Japan; 3The University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, USA; 4Japanese Red Cross Nagoya Daiichi Hospital, Nagoya, Japan.

Arginine vasopressin (AVP) is secreted via exocytosis; however, the precise molecular mechanism underlying the exocytosis of AVP is unknown. To better understand the mechanisms of AVP secretion, here we study to identify proteins that bind with a 25 kDa synaptosomal-associated protein (SNAP25), a protein that plays a crucial role in exocytosis, in the posterior pituitary. Embryonic stem (ES) cell-derived AVP neurons were established to investigate the functions of the identified proteins. Using glutathione S-transferase (GST)-pulldown assays and proteomic analyses, we identified tomosyn as a SNAP25-binding protein in the posterior pituitary. Coimmunoprecipitation assays indicated that tomosyn formed N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes with SNAP25 and syntaxin1. Immunohistochemistry showed that tomosyn localized to the posterior pituitary. Mouse ES cells self-differentiated into AVP neurons (mES-AVP) that expressed tomosyn and two transmembrane SNARE proteins, including SNAP25 and syntaxin1. KCl increased AVP secretion in mES-AVP, and overexpression of tomosyn reduced KCl-stimulated AVP secretion. Downregulation of tomosyn with siRNA increased KCl-stimulated AVP secretion. In addition, pituitary adenylate cyclase-activating polypeptide (PACAP) increased the PKA-catalysed phosphorylation of tomosyn and thus increased AVP secretion. These results suggest that tomosyn negatively regulates AVP secretion and that phosphorylation of tomosyn by PKA is involved in tomosyn-regulated AVP secretion in mES-AVP.An important next step would be to screen for gene mutations in tomosyn in patients with idiopathic CDI. We anticipate our methods of mES-AVP culturing to provide a more sophisticated in vitro model of secretion of AVP, including application to studies of CDI-specific human samples and induced pluripotent stem cells.

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