GNLY

GNLY encodes granulysin, a secreted cytolytic and pro-inflammatory peptide expressed in natural killer cells and cytotoxic T lymphocytes upon activation, produced as alternative splice forms from a five-exon gene on chromosome 2p12–q11 (PMID:8423048, PMID:2209093). The 15 kDa pro-inflammatory form of granulysin, released from activated CD8+ T cells stimulated by IL-15, induces monocyte inflammatory cytokine secretion and disrupts intestinal epithelial barrier integrity via a paracellular mechanism that is blocked by anti-GNLY antibodies (PMID:40135938). The N-terminal signal sequence is required for correct secretory pathway localization, as a premature termination mutation (p.Trp4Ter) yields a protein that mislocalizes to the nucleus with potential toxic consequences, linking GNLY to toxic epidermal necrolysis (TEN) (PMID:31642954).

1. 1990 Medium

   Chromosomal mapping established that GNLY resides at 2p12–q11, placing it in a genomic context distinct from other cytolytic effector gene clusters and enabling subsequent cloning efforts.

   Evidence In situ hybridization on human metaphase chromosomes

   PMID:2209093

   Open questions at the time

   • Gene structure and transcript diversity were not yet characterized
   • No functional data for the encoded protein
2. 1993 Medium

   Cloning and structural analysis revealed that GNLY is a five-exon gene producing alternatively spliced transcripts (NKG5 and clone 519) encoding a secreted protein specifically upregulated in activated NK and T cells, establishing it as an activation-dependent immune effector gene.

   Evidence Genomic library screening, sequencing, 5′-flanking region analysis, and cDNA comparison

   PMID:8423048

   Open questions at the time

   • Functional roles of the encoded protein (cytolysis, antimicrobial activity) were not tested
   • Regulation by specific cytokines was not defined
3. 1999 Low

   Identification of granulysin as a mitogenic factor for endothelial cells at sub-nanomolar concentrations raised the possibility that granulysin has paracrine signaling roles beyond direct cytolysis.

   Evidence Heparin-sepharose fractionation of decidual extract, endothelial proliferation assay, protein sequencing

   PMID:10584980

   Open questions at the time

   • Single functional assay without receptor identification or signaling pathway dissection
   • No in vivo validation of angiogenic activity
   • Not independently replicated
4. 2019 Medium

   A premature termination mutation (p.Trp4Ter) demonstrated that the N-terminal signal peptide is essential for secretory pathway targeting; the truncated protein mislocalizes to the nucleus and is associated with toxic epidermal necrolysis, linking GNLY loss-of-function to severe adverse drug reactions.

   Evidence Direct sequencing of GNLY coding region and subcellular localization assay of mutant protein

   PMID:31642954

   Open questions at the time

   • Mechanism of nuclear toxicity not elucidated
   • Single patient/family study — broader population confirmation needed
   • Whether PTC-readthrough product retains partial cytolytic activity is unknown
5. 2025 Medium

   Mechanistic dissection showed that IL-15-activated CD8+ T cells produce the 15 kDa pro-inflammatory granulysin isoform, which acts in a paracrine manner to activate monocyte inflammatory responses and compromise intestinal epithelial barrier integrity — effects reversible by anti-GNLY antibodies — establishing granulysin as a mediator of tissue-damaging inflammation.

   Evidence Single-cell RNA-seq, IL-15 in vitro stimulation, monocyte co-culture, anti-GNLY antibody neutralization, epithelial barrier assays

   PMID:40135938

   Open questions at the time

   • Receptor or signaling pathway on monocytes and epithelial cells not identified
   • In vivo relevance in gut inflammation not demonstrated
   • Relative contributions of 9 kDa vs 15 kDa isoforms to barrier disruption not resolved

• The receptor(s) through which granulysin signals on monocytes and epithelial cells, the structural basis of its membrane-disrupting activity against host versus microbial membranes, and the in vivo contribution of each splice isoform to immune defense versus tissue damage remain undefined.
• No receptor identified for granulysin on target host cells
• No structural model explaining selectivity for microbial vs host membranes
• In vivo isoform-specific knockout studies lacking