Proteomic and functional analysis identifies galectin-1 as a novel regulatory component of the cytotoxic granule machinery

Secretory granules released by cytotoxic T lymphocytes (CTLs) are powerful weapons against intracellular microbes and tumor cells. Despite significant progress, there is still limited information on the molecular mechanisms implicated in target-driven degranulation, effector cell survival and composition and structure of the lytic granules. Here, using a proteomic approach we identified a panel of putative cytotoxic granule proteins, including some already known granule constituents and novel proteins that contribute to regulate the CTL lytic machinery. Particularly, we identified galectin-1 (Gal1), an endogenous immune regulatory lectin, as an integral component of the secretory granule machinery and unveil the unexpected function of this lectin in regulating CTL killing activity. Mechanistic studies revealed the ability of Gal1 to control the non-secretory lytic pathway by influencing Fas–Fas ligand interactions. This study offers new insights on the composition of the cytotoxic granule machinery, highlighting the dynamic cross talk between secretory and non-secretory pathways in controlling CTL lytic function

Galectin-1 Induces Reversible Phosphatidylserine Exposure at the Plasma Membrane

Cells normally undergo physiological turnover through the induction of apoptosis and phagocytic removal, partly through exposure of cell surface phosphatidylserine (PS). In contrast, neutrophils appear to possess apoptosis-independent mechanisms of removal. Here we show that Galectin-1 (Gal-1) induces PS exposure independent of alterations in mitochondrial potential, caspase activation, or cell death. Furthermore, Gal-1–induced PS exposure reverts after Gal-1 removal without altering cell viability. Gal-1–induced PS exposure is uniquely microdomain restricted, yet cells exposing PS do not display evident alterations in membrane morphology nor do they exhibit bleb formation, typically seen in apoptotic cells. Long-term exposure to Gal-1 prolongs PS exposure with no alteration in cell cycle progression or cell growth. These results demonstrate that Gal-1–induced PS exposure and subsequent phagocytic removal of living cells represents a new paradigm in cellular turnover

Proteomic and functional analysis identifies galectin-1 as a novel regulatory component of the cytotoxic granule machinery

Secretory granules released by cytotoxic T lymphocytes (CTLs) are powerful weapons against intracellular microbes and tumor cells. Despite significant progress, there is still limited information on the molecular mechanisms implicated in target-driven degranulation, effector cell survival and composition and structure of the lytic granules. Here, using a proteomic approach we identified a panel of putative cytotoxic granule proteins, including some already known granule constituents and novel proteins that contribute to regulate the CTL lytic machinery. Particularly, we identified galectin-1 (Gal1), an endogenous immune regulatory lectin, as an integral component of the secretory granule machinery and unveil the unexpected function of this lectin in regulating CTL killing activity. Mechanistic studies revealed the ability of Gal1 to control the non-secretory lytic pathway by influencing Fas?Fas ligand interactions. This study offers new insights on the composition of the cytotoxic granule machinery, highlighting the dynamic cross talk between secretory and non-secretory pathways in controlling CTL lytic function.Fil: Clemente, Tiago. Universidade de Sao Paulo; Brasil. Instituto Nacional de Ciência e Tecnologia ; BrasilFil: Vieira, Narcisio J.. Universidade de Sao Paulo; Brasil. Instituto Nacional de Ciência e Tecnologia ; BrasilFil: Cerliani, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Adrain, Colin. Instituto Gulbenkian de Ciência; PortugalFil: Luthi, Alexander. Trinity College; IrlandaFil: Dominguez, Mariana. Universidade de Sao Paulo; BrasilFil: Yon, Monica. Universidade de Sao Paulo; BrasilFil: Barrence, Fernanda C.. Universidade de Sao Paulo; BrasilFil: Riul, Thalita B.. Universidade de Sao Paulo; BrasilFil: Cummings, Richard D.. Harvard Medical School; Estados UnidosFil: Zorn, Thelma. Universidade de Sao Paulo; BrasilFil: Amigorena, Sebastian. Inserm; FranciaFil: Dias Baruffi, Marcelo. Universidade de Sao Paulo; BrasilFil: Rodriguez, Mauricio M.. Universidade de Sao Paulo; BrasilFil: Seamus, J. Martin. Trinity College; IrlandaFil: Rabinovich, Gabriel Adrián. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Amarante Mendez, Gustavo P.. Trinity College; Irlanda. Universidade de Sao Paulo; Brasil. Instituto Nacional de Ciência e Tecnologia ; Brasi