Fig. 6: Proposed mechanism and function of MCEGs.
From: Mast cell extracellular granules are bioactive condensates assembled by heparin and polyamine
MCEGs are assembled through electrostatic interactions between heparin and spermine. The storage of proteases and cytokines within MCEGs relies on heparin–spermine condensation. Reconstituted granules comprising heparin and spermine can efficiently capture mediators such as CPA3 and TNF, enhancing their respective enzymatic and bioactive potency. The enhanced functionality stems from the distinct electrochemical microenvironment formed within the heparin–spermine condensate, marked by elevated pH and enriched metal ions. Collectively, MCEGs represent functionally active condensates that serve as storage depots while facilitating biochemical reactions and mediating immune responses. Schematic created in BioRender; Xiong, Y. https://biorender.com/qxa3cnh (2025).
