Functions as a calcium- and diacylglycerol (DAG)-regulated nucleotide exchange factor specifically activating Ras through the exchange of bound GDP for GTP. Activates the Erk/MAP kinase cascade. Regulates T-cell/B-cell development, homeostasis and differentiation by coupling T-lymphocyte/B-lymphocyte antigen receptors to Ras. Regulates NK cell cytotoxicity and ITAM-dependent cytokine production by activation of Ras-mediated ERK and JNK pathways (By similarity). Functions in mast cell degranulation and cytokine secretion, regulating FcERI-evoked allergic responses (PubMed:17190838). May also function in differentiation of other cell types. Proto-oncogene, which promotes T-cell lymphomagenesis when its expression is deregulated (PubMed:15829980, PubMed:17210708). Autoinhibited. Activated by diacylglycerol and calcium binding, which induces a conformational change releasing the autoinhibitory state. Regulated by DGKA. Regulated by DGKZ. Regulated by PLC gamma and F-actin polymerization (By similarity). Homodimer. Forms a signaling complex with DGKZ and HRAS. Interacts with F-actin. Interacts with SKAP1 (By similarity). Found both in the cytosol and associated with membranes. Relocalization to the cell membrane upon activation is F-actin-dependent (By similarity). Translocates to the Golgi in response to phorbol ester or nerve growth factor. Localizes to somata and dendrites but not to axons of hippocampal pyramidal cells (By similarity). Detected in spleen and thymus. Expressed by mature thymocytes and to a lower extent by bone marrow-derived mast cells (at protein level). Detected in B-cells and keratinocytes (at protein level). Up-regulated at the double-negative to double-positive transition during thymocyte development. Down-regulated by 12-O-tetradecanoylphorbol-13-acetate (TPA). The phorbol-ester/DAG-type zinc finger is the principal mediator of the targeting to membranes and is required for functional activation through DAG-binding. Two EF-hand domains are present. However, only EF-hand 1 (and not EF-hand 2) binds calcium. Mice fail to mount anaphylactic allergic reactions and display chronic T-cell immunodeficiencies. Lag (lymphoproliferation-autoimmunity-glomerulonephritis) mice do not express Rasgrp1 and display a systemic lupus erythematosus-like phenotype. Belongs to the RASGRP family. Was reported that thymocytes isolated from a RasGRP1 mutant mouse strain show a defect in Ras activation following T-cell-receptor (TCR) engagement (PubMed:12932358). However, this paper has been retracted because the data in one figure was falsified by one of the authors (PubMed:22808526). The authors stand by the validity of the other figures, results and interpretation in this paper (PubMed:22808526). Furthermore, evidence supporting function is derived by similarity with the human ortholog, so may be true.