Localization of the small monomeric GTPases Rab3D and Rab3A in the AtT- 20 rat pituitary cell line

Submitted: 29 December 2009
Accepted: 29 December 2009
Published: 30 December 2009
Abstract Views: 561
PDF: 1085
Publisher's note
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

Authors

We investigated the cellular localization of the small GTPases Rab3D and Rab3A in AtT-20 cells treated with the drug Brefeldin A. Brefeldin A induces the redistribution of the Golgi complex into the endoplasmic reticulum and tubulation of endosomes. However, in Brefeldin A-treated wild-type AtT-20 cells, both Rab3D and Rab3A retained their distribution, indicating that they belong to a nonendosomal, post-Golgi compartment. Immunoelectron microscopy experiments indicated that both Rab3D and Rab3A localized to the ACTH-containing, large dense core granules. In contrast, in cell clones overexpressing a mutated form of Rab3D (Rab3D N135I), Rab3A did not localize to the dense core granules. Moreover, since our previous results showed that overexpression of Rab3D N135I severely impaired regulated ACTH secretion in AtT- 20 cells, we sought to determine whether the impairment could depend on a redistribution of two key components of the regulated exocytosis machinery, synaptotagmin and SNAP-25. As far as synaptotagmin was concerned, in cell clones overexpressing Rab3D N135I, the protein did not localize close to the plasma membrane, in agreement with the previously reported defective docking of dense core granules to the plasma membrane. Immunofluorescence experiments showed that SNAP-25 did not change its localization in these cell clones. All in all, our findings strengthen the notion that both Rab3D and Rab3A are associated with the dense core granule compartment of AtT-20 cells, and that the impairment in the ACTH secretion caused by overexpression of a mutated Rab3D form is likely to be due to a lacking of granule docking to the plasma membrane, possibly because Rab3A fails to associate with the granules.

Dimensions

Altmetric

PlumX Metrics

Downloads

Download data is not yet available.

Citations

How to Cite

Tabellini, G., Baldini, G., Baldini, G., Bortul, R., Bareggi, R., Narducci, P., & Martelli, A. (2009). Localization of the small monomeric GTPases Rab3D and Rab3A in the AtT- 20 rat pituitary cell line. European Journal of Histochemistry, 45(4), 347–56. https://doi.org/10.4081/1643