CAVEOLAE AND CLATHRIN-COATED VESICLES: TWO POSSIBLE INTERNALIZATION PATHWAYS FOR IFN-GAMMA AND IFN-GAMMA RECEPTOR

Abstract

Interferon-gamma (IFN-γ) elicits a variety of activities following binding to its cell-surface-specific receptor (IFN-γR). This complex formation leads to the activation of the Jak-STAT pathway. Several hypotheses have been proposed to explain the role and location of the receptor and its ligand in the signalling pathway. In vivo as well as in vitro, the present study shows that IFN-γ and its receptor were internalized in different cellular compartments including cytoplasmic matrix, mitochondria and nucleus. In order to analyse the internalization pathway of IFN-γ and its receptor, we have study in vivo and in vitro their colocalization with clathrin and caveolin by using double immunogold-labelling experiments using electron microscopy. We demonstrate that IFN-γ and IFN-γR were colocalized in the caveolin-containing structures and the clathrin-coated pits suggesting that both internalization pathways may be used. This indicates that IFN-γ and IFN-γR were internalized by these two different pathways, suggesting two different intracellular routes probably for different target cell-compartments.