Structural Model for p75NTR–TrkA Intracellular Domain Interaction: A Combined FRET and Bioinformatics Study

• Published in: Journal of molecular biology 2011-12, Vol.414 (5), p.681-698
• Main Authors: Iacaruso, María Florencia, Galli, Soledad, Martí, Marcelo, Villalta, Jorge Ignacio, Estrin, Darío Ariel, Jares-Erijman, Elizabeth Andrea, Pietrasanta, Lía Isabel
• Format: Article
• Language: English
• Subjects: binding sites; bioinformatics; cell membranes; embryogenesis; energy transfer; heterodimerization; molecular dynamics; nerve growth factor; NGF receptors; physical association; receptors; signal transduction; structural model; vertebrates
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2011.09.022

Nerve growth factor (NGF) is a member of the neurotrophins, which are important regulators of embryonic development and adult function in the vertebrate nervous systems. The signaling elicited by NGF regulates diverse activities, including survival, axon growth, and synaptic plasticity. NGF action is mediated by engagement with two structurally unrelated transmembrane receptors, p75NTR and TrkA, which are co-expressed in a variety of cells. The functional interactions of these receptors have been widely demonstrated and include complex formation, convergence of signaling pathways, and indirect interaction through adaptor proteins. Each domain of the receptors was shown to be important for the formation of TrkA and p75NTR complexes, but only the intramembrane and transmembrane domains seemed to be crucial for the creation of high-affinity binding sites. However, whether these occur through a physical association of the receptors is unclear. In the present work, we demonstrate by Förster resonance energy transfer that p75NTR and TrkA are physically associated through their intracellular (IC) domains and that this interaction occurs predominantly at the cell membrane and prior to NGF stimulation. Our data suggest that there is a pool of receptors dimerized before NGF stimulus, which could contribute to the high-affinity binding sites. We modeled the three-dimensional structure of the TrkA IC domain by homology modeling, and with this and the NMR-resolved structure of p75NTR, we modeled the heterodimerization of TrkA and p75NTR by docking methods and molecular dynamics. These models, together with the results obtained by Förster resonance energy transfer, provide structural insights into the receptors' physical association. [Display omitted] ► p75NTR and TrkA are physically associated through their IC domains. ► This interaction occurs predominantly at the cell membrane, prior to NGF stimulation. ► The three-dimensional structure of the TrkA IC domain was obtained by homology modeling. ► TrkA and p75NTR heterodimerization was evaluated by molecular dynamics.