Trogocytosis - Mechanisms of Trogocytosis

Mechanisms of Trogocytosis

Trogocytosis involves the transfer of plasma membrane fragments from the presenting cell to the lymphocyte. Trogocytosis is specifically triggered by antigen receptor signalling on T and B cells, by killer inhibitory and killer activatory receptor on NK cells and by various receptors on other cells including Fc receptor and scavenger class A receptor. It is likely that trogocytosis does not involve the capture of vesicles such as exosomes secreted by antigen-presenting cells. Rather, molecules could move from antigen-presenting cells to lymphocytes conveyed by membrane nanotubes or membrane fragments could be torn by T cells due to physical forces required for immunological synapse formation and deformation. Depending on the two cell types involved in conjugates, trogocytosis can be unidirectional or bidirectional. Proteins transferred by trogocytosis are many and mostly include proteins inserted in or closely associated to the plasma membrane (proteins spanning the lipid bilayer or inserted in the extracellular or intracellular leaflets). For instance, human lymphocytes were recently shown to acquire the inner-membrane protein H-Ras, a G-protein vital for common lymphocyte functions and a prominent participant in human cancer, from the cells they scan. The transfer was cell contact-dependent and occurred in the context of cell-conjugate formation. Moreover, the acquisition of oncogenic H-RasG12V by NK- and T lymphocytes had important biological functions in the adopting lymphocytes: the transferred H-RasG12V induced ERK phosphorylation, increased interferon-γ and tumor necrosis factor-α secretion, enhanced lymphocyte proliferation, and augmented NK-mediated target cell killing.