Physical transfer of membrane and cytoplasmic components as a general mechanism of cell-cell communication.

Recent evidence from different research areas has revealed a novel mechanism of cell-cell communication by spontaneous intercellular transfer of cellular components (ICT). Here we studied this phenomenon by co-culturing different cells that contain distinct levels of proteins or markers for the plasma membrane or cytoplasm. We found that a variety of transmembrane proteins are transferable between multiple cell types. Membrane lipids also show a high efficiency of intercellular transfer. Size-dependent cytoplasmic transfer allows exchange of cytoplasmic macromolecules up to 40 kDa between somatic cells, and up to 2000 kDa between uncommitted human precursor cells and human umbilical vein endothelial cells. Protein transfer, lipid transfer and cytoplasmic component transfer can occur simultaneously and all require direct cell-cell contact. Analyses of the properties of ICT, together with a close examination of cell-cell interactions, suggest that the spontaneous ICT of different cellular components might have a common underlying process: transient local membrane fusions formed when neighboring cells undergo close cell-cell contact.