Human TrkB Reporter Assay Kit

Target Background

Tropomyosin receptor kinases A, B and C constitute a family of receptors denoted as TrkA, TrkB, and TrkC. Trk’s are single-pass transmembrane receptors that contain an extracellular ligand-binding domain, transmembrane domain, and an intracellular tyrosine kinase domain. Neurotrophins, the physiological activators of Trk receptors, comprise a group of proteins that include Nerve Growth Factor beta (NGF-β), Neurotrophin 3 (NT-3), Neurotrophin 4 (NT-4) and Brain Derived-Neurotrophic Factor (BDNF). The active forms of these neurotrophins are disulfide-linked homodimer polypeptides. The binding of neurotrophins to Trk’s triggers receptor homodimerization and autophosphorylation. The intrinsic tyrosine kinase activities of activated, dimeric Trk receptor initiate intracellular signaling cascades that include RAS-MAPK, PI3-AKT, and PLCγ pathways. Trk’s are expressed in multiple tissue types, and are primarily involved in neuronal development, neuronal proliferation, and avoidance of programmed cell death. Chromosomal rearrangements of NTRK1-3 may result in gene fusions have been clinically validated as oncogenic drivers in a wide array of human cancers. TrkB receptors are the most prominently expressed Trk isotype in the brain, and bind BDNF and NT-4 with similar affinities. Recent studies have identified a direct link between reduced neurotrophin levels and development of cognitive illnesses like Alzheimer’s disease (AD). Not surprising, the Trk receptors command much interest as targets for drug development and drug safety screening. Indeed, small molecule neurotrophin mimics have shown promise as an emerging therapeutic for AD. In addition, the FDA has recently approved Trk inhibitors for the treatment of patients with solid tumors harboring NTRK gene fusions.

INDIGO’s TrkB Reporter Cells include the luciferase reporter gene functionally linked to tandem consensus sequences of NFAT genetic response elements upstream of a minimal promoter. Activated NFAT binds to these response elements to seed the formation of a complete transcription complex that drives Luc gene expression. Thus, quantifying changes in luciferase expression in the treated reporter cells provides a sensitive surrogate measure of the changes in human TrkB activity.

Therefore, the principal application of this reporter assay is in the screening of test compounds to quantify any functional activity that they may exert against TrkB, or the coupled Ca+2∙calcineurin / NFAT signal transduction pathway.