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

MARÍA FLORENCIA IACARUSO; SOLEDAD GALLI ; MARCELO MARTÍ ; JORGE IGNACIO VILLALTA; DARÍO ARIEL ESTRIN; ELIZABETH ANDREA JARES-ERIJMAN; LÍA ISABEL PIETRASANTA

JOURNAL OF MOLECULAR BIOLOGY

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Año: 2011 vol. 414 p. 681 - 698

0022-2836

Abstract 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. © 2011 Elsevier Ltd. All rights reserved