Sweet kiss of dying cell: sialidase activity on apoptotic cell is able to act toward its neighbors.

Apoptotic cells and subcellular microparticles expose increased sialidase activity on their surfaces, which results from caspase-3 dependent activation of plasma membrane associated Neuraminidase-1 (Neu1). Desialylation of dying cells is also known to promote efferocytosis. The intriguing question remained whether sialidase on the surface of dying cell merely acts on self targets (cis-action), or whether it can also cleave glycoepitopes of neighboring cells (trans-action). Here, we co-incubated human viable and apoptotic Jurkat lymphocytes or neutrophils with human erythrocytes and evaluated their glycoprofile for terminal sialic acids by agglutination assay, flow cytometry, ELISA and dot-blot analyses. Data suggest that erythrocytes were desialylated as soon as 3 hours after co-incubation with apoptotic cells, but not with viable ones. After co-incubation of L929 murine fibroblasts with viable or apoptotic murine L1210 cells the L929 cells gained a desialylated glycoprofile, only after co-incubation with apoptotic cells. Our data suggests that activated sialidase(s) on the surfaces of apoptotic cells are capable to desialylate neighboring cells in trans.