Signalling pathway
Follow the endogenous signal, then distinguish receptor biology from evidence of benefit in humans.
Updated: 2026-09-16
Each edge below comes from an agent-specific source. Status and receptor pharmacology are verified separately.
| Molecule | Type | Receptor / target | Relation | Evidence class | Sources |
|---|
NGF, nerve growth factor, is an endogenous protein important for sensory and sympathetic neurons. Mature NGF interacts with TrkA (NTRK1) and p75 (NGFR). Its precursor proNGF can have different biological effects, depending on the receptor complex and experimental context. NGF: record (opens in a new tab)
Mature NGF binds TrkA, a receptor tyrosine kinase. Receptor activation connects to RAS–MAPK, PI3K–AKT and PLCγ signaling. These are cellular pathways, not clinical outcome measures. The sequence shown is one mature human chain: precursor residues 122–241, 120 amino acids. The receptor length (796 amino acids) refers to its canonical precursor; it does not describe every isoform. The diagram shows one selected interaction, not the complete receptor network. NGF (opens in a new tab) · TrkA (opens in a new tab)
A randomized, placebo-controlled early human study tested single systemic doses of recombinant human NGF in healthy volunteers. Muscle pain varied with dose. Subcutaneous administration caused local increased pain sensitivity that could persist for weeks. This was a safety and biological-response experiment, not evidence of cognitive improvement. NGF: study (opens in a new tab)
The route and formulation belong to the evidence. A result after systemic recombinant NGF cannot simply be assigned to a nasal product, an eye preparation or a substance said to increase NGF. The study also shows why a protein that supports neurons can still cause unwanted effects when administered. NGF: record (opens in a new tab)
The GK-2 article separates compound identity, experimental findings and remaining uncertainties.