Simon Sedej (Author), Maša Skelin (Author), Oliver Schlüter (Author), Marjan Rupnik (Author)

Abstract

Rab3a is a small GTPase of the Rab3 subfamily that acts during late stages of Ca2+-regulated exocytosis. Previous functional analysis in pituitary melanotrophs described Rab3a as a positive regulator of Ca2+-dependent exocytosis. However, the precise role of the Rab3a isoform on the kinetics and intracellular [Ca2+] sensitivity of regulated exocytosis, which may affect the availability of two major peptide hormones, -melanocyte stimulating hormone (-MSH) and -endorphin in plasma, remain elusive. We employed Rab3a knock-out mice (Rab3a KO) to explore the secretory phenotype in melanotrophs from fresh pituitary tissue slices. High resolution capacitance measurements showed that Rab3a KO melanotrophs possessed impaired Ca2+-triggered secretory activity as compared to wild-type cells. The hampered secretion was associated with the absence of cAMP-guanine exchange factor II/ Epac2-dependent secretory component. This component has been attributed to high Ca2+-sensitive release-ready vesicles as determined by slow photo-release of caged Ca2+. Radioimmunoassay revealed that -MSH, but not -endorphin, was elevated in the plasma of Rab3a KO mice, indicating increased constitutive exocytosis of -MSH. Increased constitutive secretion of -MSH from incubated tissue slices was associated with reduced -MSH cellular content in Rab3a-deficient pituitary cells. Viral re-expression of the Rab3a protein in vitro rescued the secretory phenotype of melanotrophs from Rab3a KO mice. In conclusion, we suggest that Rab3a deficiency promotes constitutive secretion and underlies selective impairment of Ca2+-dependent release of -MSH.

Keywords

melanotrophs;exocytosis;

Data

Language: English
Year of publishing:
Typology: 1.01 - Original Scientific Article
Organization: UM MF - Faculty of Medicine
UDC: 612
COBISS: 512349240 Link will open in a new window
ISSN: 1932-6203
Views: 939
Downloads: 364
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Other data

Secondary language: Slovenian
Secondary keywords: melanotrofi;eksocitoza;
URN: URN:SI:UM:
Type (COBISS): Scientific work
Pages: str. 1-12
Volume: ǂVol. ǂ8
Issue: ǂiss. ǂ10
Chronology: 2013
DOI: 10.1371/journal.pone.0078883
ID: 10843444