May play a role in early endosome fusion upstream of RAB5, hence regulating receptor trafficking and fluid-phase transport. Enhances cellular sensitivity to TNF-induced apoptosis (PubMed:18288467). May interact with EEA1. Colocalizes with EEA1 and RAB5 at endosomal membrane fusion hot spots (PubMed:19995552). May translocate to the endoplasmic reticulum in the early phase of apoptosis (PubMed:18288467). Expressed in placenta, ovary and small intestine, as well as in heart and pancreas. Also expressed in peripheral blood mononuclear cells and dendritic cells. Up-regulated by TNF, bacterial lipopolysaccharides (LPS) and phorbol myristate acetate (PMA) (at protein level). The PH and FYVE domains may be important for TNF-induced localization to the endoplasmic reticulum and for enhanced cellular sensitivity to TNF-induced apoptosis (PubMed:18288467). The FYVE domain is important for binding to the endosomal membrane.