STEEP1 (STING1 ER exit protein 1) is a molecular adapter protein located on the endoplasmic reticulum that functions as a critical regulator of protein trafficking and innate immune signaling. Its primary role is to stimulate membrane curvature formation and establish endoplasmic reticulum exit sites (ERES) by recruiting the PI3K complex I, thereby facilitating COPII vesicle-mediated transport 1. STEEP1 specifically promotes the ER exit of cGAMP-activated STING1 oligomers, which is the rate-limiting step in STING signaling 1. Mechanistically, STEEP1 associates with STING and stimulates phosphatidylinositol-3-phosphate (PtdIns(3)P) production to induce membrane curvature necessary for ER-to-Golgi trafficking 1. Beyond STING, STEEP1 demonstrates broader relevance as a host dependency factor for Epstein-Barr virus pathogenesis, where it supports Latent membrane protein 1 (LMP1) trafficking to intracellular signaling sites and promotes NF-κB and MAP kinase pathway activation 2. Clinically, STEEP1 mutations are associated with X-linked intellectual developmental disorder 107, though loss-of-function appears to be the proposed disease mechanism 3. STEEP1's role in supporting both viral and host immune signaling mechanisms makes it a potential therapeutic target for managing viral infections and associated malignancies.