Granulysiini

Granulysiini, known in English as granulysin (GNLY), is a cytolytic protein stored in the secretory granules of natural killer (NK) cells and CD8+ cytotoxic T lymphocytes. It belongs to the saposin-like protein (SAPLIP) family and is produced as a precursor that is proteolytically processed into at least two active isoforms.

Upon recognition of a target cell, NK cells and CTLs release granules containing perforin, granzymes, and granulysin. Granulysin contributes to cytotoxicity directly by disrupting microbial or cellular membranes and indirectly by facilitating entry of granzymes into the cytosol. It has antimicrobial activity against a variety of intracellular pathogens, including bacteria and parasites, and also participates in tumor cell killing and virus-infected cell elimination.

Granulysin expression is upregulated in activated NK cells and cytotoxic T cells, and it is stored in cytotoxic granules before degranulation. The protein can be processed into multiple isoforms, with the major forms differing in size and potency.

Clinically, granulysin is of interest as a component of the host defense system. Altered granulysin expression has been observed in some immune disorders and infections, and the molecule is studied for its potential roles in immunotherapy and as a biomarker of cytotoxic lymphocyte activity.