Granulysin

Granulysin is a cytolytic and antimicrobial protein encoded by the GNLY gene. It belongs to the saposin-like protein family and is found in the cytotoxic granules of natural killer (NK) cells and cytotoxic T lymphocytes.

In healthy individuals, granulysin is produced by NK cells and CD8+ T cells and stored in cytolytic granules along with perforin and granzymes. Upon recognition of infected or transformed cells, these granules release granulysin into the immunological synapse to exert its effects.

Granulysin has direct antimicrobial activity, binding to and disrupting membranes of intracellular bacteria, fungi, and parasites and contributing to pathogen clearance. It can also promote apoptosis in target cells and acts in concert with perforin. Additionally, granulysin can modulate immune responses by activating macrophages and dendritic cells.

The protein is part of the saposin-like protein family and is produced as a precursor that is processed to active forms. Human granulysin exists in multiple active forms generated by proteolytic processing. The GNLY gene and granulysin orthologs have been studied across primates.

Clinically, granulysin is studied for its role in defense against intracellular pathogens such as Mycobacterium and Listeria and for its potential involvement in tumor immunity. It remains an area of active research for antimicrobial and immunomodulatory therapies.