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The involvement of RACK1 in the release of mast cell mediators.

Grant number: 17/14645-4
Support type:Regular Research Grants
Duration: September 01, 2017 - November 30, 2019
Field of knowledge:Biological Sciences - Morphology - Cytology and Cell Biology
Principal researcher:Maria Célia Jamur
Grantee:Maria Célia Jamur
Home Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
Assoc. researchers:Constance Oliver

Abstract

Mast cells are immunoregulatory cells that are implicated in innate and adaptive immunity. Mast cells participate in different biological events such as host protection, angiogenesis, inflammatory and allergic reactions. The action of mast cells is related directly to their activation and subsequent mediator release. The best characterized mast cell activation pathway is that via the high-affinity receptor for immunoglobulin E (FcµRI). Binding of a multivalent antigen to immunoglobulin E (IgE) that is already bound to FcµRI results in the crosslinking of FcµRI and the initiation of intracellular signaling events. Although there have been many previous studies related to the molecular mechanisms of mast cell activation, the function of some regulatory proteins involved in mast cell signal transduction remain unknown. RACK1 (Receptor for Activated C Kinase 1) is a highly conserved intracellular adaptor protein that interacts with signaling proteins (kinases and phosphatases), transcriptional factors and the cytoplasmic domains of transmembrane proteins. As a scaffold protein, RACK1 integrates inputs from distinct signaling pathways and actively participates in signal transduction. Earlier studies have shown that RACK1 participates in the activation of immune cells and regulates the inflammatory response. Protein-protein interaction networks associated with asthma identified the gene GNB2L1, which encodes RACK1 protein, as a target gene related to cellular signaling in asthma. Acute asthma involves atopic and anaphylactic reactions triggered by mast cells. RACK1 is required as a scaffold protein for several signaling proteins that are engaged during mast cell activation. Recent data obtained in our laboratory identified, for the first time, the presence of RACK1 in RBL-2H3 mast cells. RACK1 is located in lipid rafts and is up regulated when GD1b-derived gangliosides are removed from these microdomains. Our preliminare results show that f RACK1 is present in mast cells in mouse lung, mouse bone marrow-derived mast cells (BMMCs) and the in rat mast cell line RBL-2H. RACK1 was localized in a punctate manner throughout the cytoplasm and also found in the nuclei. Furthermore, after activation via FcµRI for short time periods, RACK1 increased in regions adjacent to the plasma membrane but is reduced in the nuclei. These findings suggest that RACK1 may be involved in the organization and function of signaling complexes in lipid rafts, as well as, in signal transduction pathways that regulates the release of inflammatory mediators in mast cells. The present study aims to characterize the functional role of RACK1 in mast cell activation and migration, which is required during allergy and inflammation. The role of RACK1 in mast cells will be investigated using interference RNAs in RBL-2H3 mast cells. An understanding of the role of RACK1 in mast cell activation may lead to new therapeutic targets for allergic and inflammatory process. (AU)

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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)
FREITAS FILHO, EDISMAURO G.; DA SILVA, ELAINE Z. M.; ONG, HWEI LING; SWAIM, WILLIAM D.; AMBUDKAR, INDU S.; OLIVER, CONSTANCE; JAMUR, MARIA CELIA. RACK1 plays a critical role in mast cell secretion and Ca2+ mobilization by modulating F-actin dynamics. Journal of Cell Science, v. 134, n. 9 MAY 2021. Web of Science Citations: 1.
FREITAS FILHO, EDISMAURO GARCIA; MARIN JACA, LUIZ AUGUSTO; BAEZA, LILIAN CRISTIANE; DE ALMEIDA SOARES, CELIA MARIA; BORGES, CLAYTON LUIZ; OLIVER, CONSTANCE; JAMUR, MARIA CELIA. Proteomic Analysis of Lipid Rafts from RBL-2H3 Mast Cells. INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, v. 20, n. 16 AUG 2 2019. Web of Science Citations: 0.

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