NGB

Neuroglobin (NGB) is a neuroprotective globin that defends neurons and retinal tissue against hypoxic, oxidative, and inflammatory injury (PMID:23456442, PMID:31827177). Upon stress, exogenously delivered NGB suppresses the mitochondria-dependent apoptotic pathway, increasing Bcl-2 expression while reducing caspase-3 and caspase-9 activities, and protects primary cortical neurons from hypoxia-induced death (PMID:23456442). NGB-mediated protection engages the PI3K/Akt/CREB signaling axis, and CREB in turn directly binds the Ngb promoter to upregulate Ngb transcription, establishing a feed-forward loop in which Ngb is both effector and transcriptional target of survival signaling (PMID:34751416). A manganese-porphyrin-reconstituted NGB fusion enhances ROS scavenging and restores mitochondrial function while activating PI3K/Akt to drive an Nrf2/HO-1/SOD/catalase antioxidant program (PMID:31882813), and the same agent suppresses LPS-induced inflammation by blocking NF-κB nuclear translocation, attenuating MAPK signaling, and preventing NLRP3 inflammasome assembly to limit IL-1β and IL-18 production (PMID:32470548). In retinal hypoxia, restoring NGB lowers inflammatory chemokines and microglial activation, confirming a direct anti-inflammatory role (PMID:31827177). The available corpus also contains a distinct GTP-binding protein designated NGB (NF2-associated GTP-binding protein) that physically interacts with the NF2 tumor suppressor merlin to impair its turnover and acts as a tumor suppressor by inhibiting schwannoma growth and cyclin D1 expression (PMID:17210637); this entity is mechanistically unrelated to the globin and reflects a shared symbol.

1. 2007 Medium

   Established that a GTP-binding protein named NGB binds the NF2 tumor suppressor merlin and functions in growth suppression, defining a tumor-suppressor role for this symbol-sharing entity.

   Evidence Reciprocal co-immunoprecipitation, GTPase assays, and gain/loss-of-function growth, aggregation, and tumorigenicity assays in schwannoma cells

   PMID:17210637

   Open questions at the time

   • Single lab; relationship (if any) to the neuroprotective globin NGB is not addressed
   • Mechanism by which NGB stabilizes merlin not resolved beyond impaired turnover
2. 2013 Medium

   Showed that NGB protein delivered directly into neurons suppresses the mitochondrial apoptotic pathway, moving NGB from a correlate of survival to a sufficient protective effector.

   Evidence TAT PTD-Ngb fusion delivery with viability, ultrastructure, caspase activity, and Bcl-2 Western blot in primary cortical neurons under hypoxia

   PMID:23456442

   Open questions at the time

   • Single lab
   • Upstream signaling linking Ngb to Bcl-2/caspase changes not defined in this study
3. 2013 Low

   Correlated high Ngb levels with Akt/CREB activation and reduced apoptosis in vivo, implicating a survival signaling axis but without direct Ngb manipulation.

   Evidence Western blot, co-IP, immunohistochemistry, and TUNEL in an Alzheimer's disease rat model with pharmacological intervention

   PMID:23428737

   Open questions at the time

   • Correlative with no direct Ngb gain/loss-of-function
   • Cannot distinguish cause from consequence in the Akt/CREB association
4. 2019 Medium

   Demonstrated that a ROS-scavenging-enhanced NGB fusion restores mitochondrial function and activates a PI3K/Akt-Nrf2 antioxidant program, linking NGB to redox defense.

   Evidence ROS scavenging, mitochondrial function and apoptosis assays, and PI3K/Akt/Nrf2/HO-1/SOD/CAT Western blots in cell culture (Mn-TAT PTD-Ngb)

   PMID:31882813

   Open questions at the time

   • Uses an engineered Mn-porphyrin fusion rather than native Ngb
   • Single lab; in vivo relevance not established here
5. 2019 Medium

   Established a direct anti-inflammatory role for NGB in tissue, distinct from its cell-autonomous antiapoptotic action.

   Evidence Intravitreal Ngb protein replacement with chemokine ELISA, microglial immunohistochemistry, ERG, and histology in rat retinal hypoxia

   PMID:31827177

   Open questions at the time

   • Single lab
   • Molecular mechanism connecting Ngb to chemokine suppression not dissected in this model
6. 2020 Medium

   Defined the molecular anti-inflammatory mechanism of NGB, tying it to NF-κB, MAPK, and NLRP3 inflammasome suppression.

   Evidence NF-κB translocation, MAPK Western blot, ROS, mitochondrial, inflammasome assembly, and cytokine ELISA in LPS-stimulated cells (Mn-TAT PTD-Ngb)

   PMID:32470548

   Open questions at the time

   • Engineered fusion rather than native protein
   • Single lab; direct versus ROS-indirect contributions to inflammasome suppression not separated
7. 2021 Medium

   Closed a regulatory loop by showing CREB directly binds the Ngb promoter to drive its transcription, making Ngb both target and effector of Akt/CREB survival signaling.

   Evidence Luciferase reporter, ChIP, AKT/CREB phosphorylation Western blots, siRNA knockdown rescue, and ROS/viability assays in neuronal cells (polydatin)

   PMID:34751416

   Open questions at the time

   • Single lab
   • Whether other transcription factors co-regulate the Ngb promoter is not addressed

• The relationship between the neuroprotective globin NGB and the merlin-associated GTP-binding NGB, and whether the corpus describes one protein or two distinct entities sharing a symbol, remains unresolved.
• No direct structural or mechanistic link established between the two NGB entities
• No endogenous, native-protein in vivo loss-of-function study of the globin clarifying its physiological role