NSM

TgNSM is a bradyzoite-stage secreted dense granule effector of Toxoplasma gondii that is exported into the host cell and traffics to the host nucleus, where it manipulates host transcription to sustain the chronic infection niche (PMID:34043960). In the nucleus it co-opts the NCoR/SMRT transcriptional repressor complex to suppress IFN-driven expression of PKR and MLKL, thereby blocking necroptosis and protecting the parasite's intracellular cyst (PMID:34043960). TgNSM additionally functions as one of eight MYR1-dependent effectors that cooperatively activate the non-canonical NF-κB pathway (RelB/p52) in host cells through TRAF3 depletion, NIK stabilization, and p100 processing, an additive network mechanism in which no single effector is solely responsible (PMID:41959509). Beyond these host-manipulation roles, no further mechanistic detail on TgNSM has been characterized in the available corpus.

1. 2021 High

   Established that TgNSM is a nuclear-targeted secreted effector whose function is to protect the chronic cyst by silencing host necroptosis, answering how the bradyzoite stage evades IFN-driven cell death.

   Evidence Genetic analysis of nucleus-localizing secreted effectors, epistasis with TgIST, and PKR/MLKL expression plus necroptosis assays in infected cells

   PMID:34043960

   Open questions at the time

   • Mechanism by which TgNSM engages NCoR/SMRT (direct binding vs. bridging) not resolved
   • Route of nuclear import and export machinery not defined in this finding
   • Whether IFN-independent targets exist is unaddressed
2. 2025 Low

   Correlated NSM protein abundance with culture adaptation and virulence factor expression, hinting that NSM levels track the parasite's virulent state but without testing function.

   Evidence Label-free LC-MS proteomics comparing low- and high-passage field isolates

   PMID:41036225

   Open questions at the time

   • Expression-correlation only; no direct mechanistic test of NSM function
   • Causal link between NSM abundance and virulence not established
   • Does not distinguish cause from consequence of adaptation
3. 2026 Medium

   Placed TgNSM within a redundant network of eight MYR1-dependent effectors that additively activate non-canonical NF-κB, clarifying that NSM's role in this pathway is cooperative rather than singular.

   Evidence Combinatorial knockout parasite panel with RelB/p52 nuclear accumulation assays and Western blots for TRAF3, NIK, and p100/p52 (preprint)

   PMID:41959509

   Open questions at the time

   • Individual contribution of NSM cannot be isolated from the other seven effectors
   • Direct molecular target of NSM in the TRAF3/NIK axis unknown
   • Preprint, not yet peer-reviewed

• How TgNSM physically engages the NCoR/SMRT complex and whether its necroptosis-blocking and NF-κB-activating activities are mechanistically linked remains unresolved.
• No structural or biochemical map of the NSM–NCoR/SMRT interaction
• No direct molecular target within the non-canonical NF-κB machinery
• Relationship between the two host-manipulation activities undefined