Internalization and nuclear translocation of IFN-gamma and IFN-gamma R: Anultrastructural approach

IFN-gamma signalling involves the Jak-STAT pathway. However, several hypoth esis have been proposed where the receptor and its ligand itself took an ac tive role within the cell. Using a quantitative immunogold approach, we fou nd that both IFN-gamma and its receptor are rapidly internalized and transl ocated in the nucleus. We found that cell surface heparan sulfate, which bi nds IFN-gamma, delayed the nuclear accumulation of IFN-gamma suggesting tha t these molecules serve as storage depot around the cell for local delivery of the cytokine, (C) 2000 Academic Press.