The function of RASGRP4 (RAS guanyl releasing protein 4, Ensembl gene identifier ENSG00000171777) is as follows. Functions as a cation- and diacylglycerol (DAG)-regulated nucleotide exchange factor activating Ras through the exchange of bound GDP for GTP (PubMed:11880369, PubMed:11956218, PubMed:12493770, PubMed:18024961). In neutrophils, participates in a phospholipase C- activating N-formyl peptide-activated GPCR (G protein-coupled receptor) signaling pathway by promoting Ras-mediated activation of PIK3CG/PI3Kgamma to promote neutrophil functional responses (By similarity). In CD117(+) dendritic cells and mast cells, participates in an lipopolysaccharide (LPS)-activated signaling pathway that stimulates the production of interferon-gamma and other pro- inflammatory cytokines by natural killer (NK) cells (By similarity). May function in mast cell differentiation (PubMed:11880369, PubMed:11956218, PubMed:12493770, PubMed:18024961). Does not appear to be required for the development of B-cells, DC-cells, T-cells, or NK- cells (By similarity). {ECO:0000250|UniProtKB:Q8BTM9, ECO:0000269|PubMed:11880369, ECO:0000269|PubMed:11956218, ECO:0000269|PubMed:12493770, ECO:0000269|PubMed:18024961}.