Internalization and nuclear translocation of IFN-gamma and IFN-gammaR: an ultrastructural approach

IFN-gamma signalling involves the Jak-STAT pathway. However, several hypothesis have been proposed where the receptor and its ligand itself took an active role within the cell. Using a quantitative immunogold approach, we found that both IFN-gamma and its receptor are rapidly internalized and translocated in the nucleus. We found that cell surface heparan sulfate, which binds IFN-gamma, delayed the nuclear accumulation of IFN-gamma suggesting that these molecules serve as storage depot around the cell for local delivery of the cytokine.