Small molecule BDNF mimetics activate TrkB signaling and prevent neuronal degeneration in rodents
Stephen M. Massa, … , Jayakumar Rajadas, Frank M. Longo
Stephen M. Massa, … , Jayakumar Rajadas, Frank M. Longo
Published April 19, 2010
Citation Information: J Clin Invest. 2010;120(5):1774-1785. https://doi.org/10.1172/JCI41356.
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Technical Advance Neuroscience

Small molecule BDNF mimetics activate TrkB signaling and prevent neuronal degeneration in rodents

Abstract

Brain-derived neurotrophic factor (BDNF) activates the receptor tropomyosin-related kinase B (TrkB) with high potency and specificity, promoting neuronal survival, differentiation, and synaptic function. Correlations between altered BDNF expression and/or function and mechanism(s) underlying numerous neurodegenerative conditions, including Alzheimer disease and traumatic brain injury, suggest that TrkB agonists might have therapeutic potential. Using in silico screening with a BDNF loop–domain pharmacophore, followed by low-throughput in vitro screening in mouse fetal hippocampal neurons, we have efficiently identified small molecules with nanomolar neurotrophic activity specific to TrkB versus other Trk family members. Neurotrophic activity was dependent on TrkB and its downstream targets, although compound-induced signaling activation kinetics differed from those triggered by BDNF. A selected prototype compound demonstrated binding specificity to the extracellular domain of TrkB. In in vitro models of neurodegenerative disease, it prevented neuronal degeneration with efficacy equal to that of BDNF, and when administered in vivo, it caused hippocampal and striatal TrkB activation in mice and improved motor learning after traumatic brain injury in rats. These studies demonstrate the utility of loop modeling in drug discovery and reveal what we believe to be the first reported small molecules derived from a targeted BDNF domain that specifically activate TrkB.We propose that these compounds constitute a novel group of tools for the study of TrkB signaling and may provide leads for developing new therapeutic agents for neurodegenerative diseases.

Authors

Stephen M. Massa, Tao Yang, Youmei Xie, Jian Shi, Mehmet Bilgen, Jeffrey N. Joyce, Dean Nehama, Jayakumar Rajadas, Frank M. Longo

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Figure 5

Comparison of BDNF’s and LM22A compound’s signaling activation kinetics and dependence of survival on downstream signaling.

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Comparison of BDNF’s and LM22A compound’s signaling activation kinetics ...
(A) Left: Representative Western blot showing activation of Trk, AKT, and ERK in cultured E16 hippocampal neurons incubated with LM22A-4 at the indicated concentrations for 60 minutes. Right: Western blot analyses were quantitated for Trk, AKT, and ERK activation (ratio of p-TrkY490, using a pan–phospho-Trk antibody, to total TrkB; p-AKT to total AKT; and p-ERK to total ERK signal). n = 15–18 Western analyses from 4–9 independent protein preparations. (B–D) Cultured E16 hippocampal neurons were incubated with BDNF (0.7 nM) or LM22A compounds (500 nM) for the indicated times, and quantitative analysis for Trk, AKT, and ERK activation was performed as in A. n = 8–11 Western blot analyses from 4–5 independent protein preparations. For each Western blot, the activation ratio induced by BDNF at the 10-minute time point was normalized to 1.0 and the other values adjusted accordingly. (E) E16 hippocampal neurons were incubated with BDNF (0.7 nM) or LM22A compounds (500 nM) for 48 hours in the presence or absence of the PI3K inhibitor LY294002 (LY, 10 μM) or the MAPK kinase inhibitor PD98059 (PD, 50 μM). For BDNF, n = 33–37 wells derived from 7 experiments were assessed. For LM22A-1, -2, and -3, n = 17–21 wells derived from 6 experiments were analyzed. For LM22A-4, n = 28–57 wells derived from 4 experiments were assessed. *P < 0.05, #P < 0.01, §P < 0.001.