Extracellular vesicles (EVs) play a key role in intercellular communication by transferring bioactive molecules from donor to recipient cells. This study explores the impact of EV fusion on cellular responses to inflammatory signaling. The findings reveal that fusion renders non-responsive cells susceptible to inflammatory signaling, as evidenced by increased NF-κB activation and the release of inflammatory mediators. Syntaxin-binding protein 1 is essential for the merge and activation of intracellular signaling. Subsequent analysis shows that EVs transfer their functionally active receptors to target cells, making them prone to an otherwise unresponsive state. EVs in complex with their agonist require no further stimulation of the target cells to trigger mobilization of NF-κB. While receptor antagonists were unable to inhibit NF-κB activation, blocking of the fusion between EVs and their target cells with heparin mitigated inflammation in mice challenged with EVs. EVs are released in patients with inflammatory complications such as poly-trauma and sepsis, and can contribute to life-threatening conditions. In vitro studies show that EVs are secreted via an exocytotic budding process in which phosphatidylserine translocates from the inner to the outer leaflet of the cell membrane. EVs have a diameter ranging from 0.1 to 2 μm and retain the same cell-surface protein pattern as found on the cells of origin. The cytosolic components of EVs contain proteins, lipids, nucleic acids (including DNA, mRNA, and non-coding RNA), and small metabolites. Because of the wide range of bioactive proteins, adhesion molecules, and membrane-anchored receptors, EVs are primed for customized crosstalk with their environment. By fusing with target cells, EVs can transfer their parent cytosolic content and are able to translocate cell membrane attached- and spanning-proteins. The fusion process requires the formation of a SNARE-complex and can be blocked by heparin. SNARE-mediated intracellular fusion involves apart from the SNARE-complex also the Syntaxin binding protein 1 (STXBP1), which is a member of the Sec1/Munc18 family. Although the exact molecular mechanism for fusion is still not completely understood, several studies have suggested that STXBP1 initially binds to SNARE subunit syntaxin-1, to form a heterodimer on the target membrane. Once the secretory vesicle or microparticle comes into close apposition with the target membrane, STXBP1 that is bound to the syntaxin-1 can assemble with VAMP2/synaptobrevin on the membrane of the EV. This pins the two membranes together and exerts the force required for a fusion-pore to open between the two membranes. With this mechanism, EVs can trigger an activation of their target cells, cause phenotypic modifications, and reExtracellular vesicles (EVs) play a key role in intercellular communication by transferring bioactive molecules from donor to recipient cells. This study explores the impact of EV fusion on cellular responses to inflammatory signaling. The findings reveal that fusion renders non-responsive cells susceptible to inflammatory signaling, as evidenced by increased NF-κB activation and the release of inflammatory mediators. Syntaxin-binding protein 1 is essential for the merge and activation of intracellular signaling. Subsequent analysis shows that EVs transfer their functionally active receptors to target cells, making them prone to an otherwise unresponsive state. EVs in complex with their agonist require no further stimulation of the target cells to trigger mobilization of NF-κB. While receptor antagonists were unable to inhibit NF-κB activation, blocking of the fusion between EVs and their target cells with heparin mitigated inflammation in mice challenged with EVs. EVs are released in patients with inflammatory complications such as poly-trauma and sepsis, and can contribute to life-threatening conditions. In vitro studies show that EVs are secreted via an exocytotic budding process in which phosphatidylserine translocates from the inner to the outer leaflet of the cell membrane. EVs have a diameter ranging from 0.1 to 2 μm and retain the same cell-surface protein pattern as found on the cells of origin. The cytosolic components of EVs contain proteins, lipids, nucleic acids (including DNA, mRNA, and non-coding RNA), and small metabolites. Because of the wide range of bioactive proteins, adhesion molecules, and membrane-anchored receptors, EVs are primed for customized crosstalk with their environment. By fusing with target cells, EVs can transfer their parent cytosolic content and are able to translocate cell membrane attached- and spanning-proteins. The fusion process requires the formation of a SNARE-complex and can be blocked by heparin. SNARE-mediated intracellular fusion involves apart from the SNARE-complex also the Syntaxin binding protein 1 (STXBP1), which is a member of the Sec1/Munc18 family. Although the exact molecular mechanism for fusion is still not completely understood, several studies have suggested that STXBP1 initially binds to SNARE subunit syntaxin-1, to form a heterodimer on the target membrane. Once the secretory vesicle or microparticle comes into close apposition with the target membrane, STXBP1 that is bound to the syntaxin-1 can assemble with VAMP2/synaptobrevin on the membrane of the EV. This pins the two membranes together and exerts the force required for a fusion-pore to open between the two membranes. With this mechanism, EVs can trigger an activation of their target cells, cause phenotypic modifications, and re