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The role of adaptor protein complex 3 (AP-3) in regulated secretion in mast cells

Grant number: 14/11396-5
Support type:Regular Research Grants
Duration: August 01, 2014 - October 31, 2016
Field of knowledge:Biological Sciences - Morphology - Cytology and Cell Biology
Principal Investigator:Constance Oliver
Grantee:Constance Oliver
Home Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
Assoc. researchers:Maria Célia Jamur

Abstract

Mast cells (MCs) are multifunctional immune cells implicated in inflammation, allergy, tissue repair and angiogenesis. MCs, along with neurons, melanocytes, endocrine and exocrine cells as well as other immune cells, are specialized secretory cells which present regulated secretion. The regulated secretory pathway requires the sorting of proteins to a specific route destined to secretory granules, which are secreted upon adequate physiological stimulation. MC involvement in various physiological and pathological processes occurs through the regulated secretion of its biological mediators, in particular, the preformed mediators stored in their secretory granules which are considered Lysosome-Related Organelles (LROs) due to several characteristics they share with lysosomes. The biogenesis of LROs is strictly related to the endolisossomal system. In this system the sorting of proteins destined to organelles, relies on signals that direct their incorporation in transport vesicles. The AP protein complex adaptors are responsible for connecting coats to the donor membrane, selecting cargo, and recruiting accessory proteins that regulate vesicle budding and trafficking. The AP-3 complex adaptor is a stable heterotetramer formed by 4 different subunits (delta, beta3, mu3 e sigma3) and is recognized for its role in the biogenesis of LROs, including melanosomes and platelet dense granules. It's believed that AP-3 acts on the traffic between the biosynthetic and endocytic pathways to late endosomes, lysosomes, and LROs. Genetic defects in the Beta3A subunit of AP-3 cause type II Hermansky-Pudlak syndrome in humans which is characterized by oculocutaneous albinism, prolonged bleeding and innate immune deficiency. These symptoms are associated with anomalies in secretory granule biogenesis and release in specialized cells including melanocytes, platelets, and cytotoxic T lymphocytes. MCs perform a great part of their functions through the regulated secretion of mediators stored in their secretory granules. Hence, the aim of this project is to investigate the direct and indirect involvement of AP-3 in the biogenesis of mast cell secretory granules, more specifically in the sorting of proteins to these organelles. The influence of AP-3 in the fusion of the granule with the plasma membrane be also investigated. This process is thought to be dependent on the correct sorting of proteins important for exocytosis in MCs. The involvement of AP-3 in MC regulated secretion will be studied through RNAi in RBL-2H3 cells. The effects of the absence of AP-3 on the traffic and secretion of granule proteins in MCs will be evaluated. Our findings will contribute to the elucidation of the role of AP-3 in MC regulated secretion. The results may also help to shed light on the contribution of MCs to the symptoms observed in HPS2. The knowledge of the molecular mechanisms involved in the biogenesis and exocytosis of MC granules are of utmost importance because the mediators contained in these granules are involved in the inflammatory and pathological processes caused or exacerbated by these cells. The understanding of theses mechanisms can lead to therapeutic targets to aid in the control of allergy and inflamation. (AU)

Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
MARCELINO DA SILVA, ELAINE ZAYAS; FREITAS-FILHO, EDISMAURO GARCIA; DE SOUZA-JUNIOR, DEVANDIR ANTONIO; PINTO DASILVA, LUIS LAMBERTI; JAMUR, MARIA CELIA; OLIVER, CONSTANCE. Adaptor protein-3: A key player in RBL-2H3 mast cell mediator release. PLoS One, v. 12, n. 3 MAR 8 2017. Web of Science Citations: 2.

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