Structural Model for p75 NTR–TrkA Intracellular Domain Interaction: A Combined FRET and Bioinformatics Study

IACARUSO, M.F.; GALLI, S.; MARTI, M.A.; VILLALTA, J.I.; ESTRIN, D.A.; JARES-ERIJMAN, E.A.; PIETRASANTA, L.I.

JOURNAL OF MOLECULAR BIOLOGY

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2011 vol. 414 p. 681 - 698

0022-2836

Nerve growth factor (NGF) is a member of the neurotrophins, which areimportant regulators of embryonic development and adult function in thevertebrate nervous systems. The signaling elicited by NGF regulates diverseactivities, including survival, axon growth, and synaptic plasticity. NGFaction is mediated by engagement with two structurally unrelatedtransmembrane receptors, p75NTR and TrkA, which are co-expressed in avariety of cells. The functional interactions of these receptors have beenwidely demonstrated and include complex formation, convergence ofsignaling pathways, and indirect interaction through adaptor proteins. Eachdomain of the receptors was shown to be important for the formation ofTrkA and p75NTR complexes, but only the intramembrane and transmembranedomains seemed to be crucial for the creation of high-affinity bindingsites. However, whether these occur through a physical association of thereceptors is unclear. In the present work, we demonstrate by Försterresonance energy transfer that p75NTR and TrkA are physically associatedthrough their intracellular (IC) domains and that this interaction occurspredominantly at the cell membrane and prior to NGF stimulation. Ourdata suggest that there is a pool of receptors dimerized before NGFstimulus, which could contribute to the high-affinity binding sites. Wemodeled the three-dimensional structure of the TrkA IC domain byhomology modeling, and with this and the NMR-resolved structure ofp75NTR, we modeled the heterodimerization of TrkA and p75NTR bydocking methods and molecular dynamics. These models, together with theresults obtained by Förster resonance energy transfer, provide structuralinsights into the receptors´ physical association.