Roles of RabGEF1/Rabex-5 domains in regulating Fc epsilon RI surface expression and Fc epsilon RI-dependent responses in mast cells. 2007

Janet Kalesnikoff, and Eon J Rios, and Ching-Cheng Chen, and M Alejandro Barbieri, and Mindy Tsai, and See-Ying Tam, and Stephen J Galli
Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5324, USA.

RabGEF1/Rabex-5, a guanine nucleotide exchange factor (GEF) for the endocytic pathway regulator, Rab5, contains a Vps9 domain, an A20-like zinc finger (ZnF) domain, and a coiled coil domain. To investigate the importance of these domains in regulating receptor internalization and cell activation, we lentivirally delivered RabGEF1 mutants into RabGEF1-deficient (-/-) mast cells and examined Fc epsilon RI-dependent responses. Wild-type RabGEF1 expression corrected phenotypic abnormalities in -/- mast cells, including decreased basal Fc epsilon RI expression, slowed Fc epsilon RI internalization, elevated IgE + Ag-induced degranulation and IL-6 production, and the decreased ability of -/- cytosol to support endosome fusion. We showed that RabGEF1's ZnF domain has ubiquitin ligase activity. Moreover, the coiled coil domain of RabGEF1 is required for Rabaptin-5 binding and for maintaining basal levels of Rabaptin-5 and surface Fc epsilon RI. However, mutants lacking either of these domains normalized phenotypic abnormalities in IgE + antigen-activated -/- mast cells. By contrast, correction of these -/- phenotypes required a functional Vps9 domain. Thus, Fc epsilon RI-mediated mast cell functional activation is dependent on RabGEF1's GEF activity.

UI MeSH Term Description Entries
D008407 Mast Cells Granulated cells that are found in almost all tissues, most abundantly in the skin and the gastrointestinal tract. Like the BASOPHILS, mast cells contain large amounts of HISTAMINE and HEPARIN. Unlike basophils, mast cells normally remain in the tissues and do not circulate in the blood. Mast cells, derived from the bone marrow stem cells, are regulated by the STEM CELL FACTOR. Basophils, Tissue,Basophil, Tissue,Cell, Mast,Cells, Mast,Mast Cell,Tissue Basophil,Tissue Basophils
D001854 Bone Marrow Cells Cells contained in the bone marrow including fat cells (see ADIPOCYTES); STROMAL CELLS; MEGAKARYOCYTES; and the immediate precursors of most blood cells. Bone Marrow Cell,Cell, Bone Marrow,Cells, Bone Marrow,Marrow Cell, Bone,Marrow Cells, Bone
D002478 Cells, Cultured Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others. Cultured Cells,Cell, Cultured,Cultured Cell
D004705 Endocytosis Cellular uptake of extracellular materials within membrane-limited vacuoles or microvesicles. ENDOSOMES play a central role in endocytosis. Endocytoses
D005786 Gene Expression Regulation Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation. Gene Action Regulation,Regulation of Gene Expression,Expression Regulation, Gene,Regulation, Gene Action,Regulation, Gene Expression
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D015550 Cell Degranulation The process of losing secretory granules (SECRETORY VESICLES). This occurs, for example, in mast cells, basophils, neutrophils, eosinophils, and platelets when secretory products are released from the granules by EXOCYTOSIS. Degranulation, Cell
D015850 Interleukin-6 A cytokine that stimulates the growth and differentiation of B-LYMPHOCYTES and is also a growth factor for HYBRIDOMAS and plasmacytomas. It is produced by many different cells including T-LYMPHOCYTES; MONOCYTES; and FIBROBLASTS. Hepatocyte-Stimulating Factor,Hybridoma Growth Factor,IL-6,MGI-2,Myeloid Differentiation-Inducing Protein,Plasmacytoma Growth Factor,B Cell Stimulatory Factor-2,B-Cell Differentiation Factor,B-Cell Differentiation Factor-2,B-Cell Stimulatory Factor 2,B-Cell Stimulatory Factor-2,BSF-2,Differentiation Factor, B-Cell,Differentiation Factor-2, B-Cell,IFN-beta 2,IL6,Interferon beta-2,B Cell Differentiation Factor,B Cell Differentiation Factor 2,B Cell Stimulatory Factor 2,Differentiation Factor 2, B Cell,Differentiation Factor, B Cell,Differentiation-Inducing Protein, Myeloid,Growth Factor, Hybridoma,Growth Factor, Plasmacytoma,Hepatocyte Stimulating Factor,Interferon beta 2,Interleukin 6,Myeloid Differentiation Inducing Protein,beta-2, Interferon
D017455 Receptors, IgE Specific molecular sites on the surface of B- and T-lymphocytes which combine with IgEs. Two subclasses exist: low affinity receptors (Fc epsilon RII) and high affinity receptors (Fc epsilon RI). Antigens, CD23,CD23 Antigens,Fc Receptors, epsilon,Fc epsilon Receptor,Fc epsilon Receptors,IgE Receptor,IgE Receptors,Receptors, Fc epsilon,epsilon Fc Receptor,epsilon Fc Receptors,CD 23 Antigens,CD23 Antigen,Fc epsilon RI,Fc epsilon RII,Immunoglobulin E Receptor,Antigen, CD23,Antigens, CD 23,Fc Receptor, epsilon,Receptor, Fc epsilon,Receptor, IgE,Receptor, Immunoglobulin E,Receptor, epsilon Fc,Receptors, epsilon Fc,epsilon RI, Fc,epsilon RII, Fc,epsilon Receptor, Fc,epsilon Receptors, Fc
D020662 Guanine Nucleotide Exchange Factors Protein factors that promote the exchange of GTP for GDP bound to GTP-BINDING PROTEINS. GDP Exchange Factors,GDP-GTP Reversing Factors,Guanine Nucleotide Releasing Factors,GDP Dissociation Factor,GDP Dissociation Stimulators,GDP-GTP Exchange Protein,Guanine Nucleotide Exchange Factor,Guanine-Nucleotide-Releasing Factor,Exchange Factors, GDP,Factors, GDP Exchange,Factors, GDP-GTP Reversing,GDP GTP Exchange Protein,GDP GTP Reversing Factors,Guanine Nucleotide Releasing Factor,Reversing Factors, GDP-GTP

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