A new paper from our lab has been published in Journal of Biological Chemistry
The interaction between TrkA and p75 is mediated by their transmembrane domains
In a great International collaboration between our lab and the labs of Dr. Alexander Arseniev in Moscow and Dr. Kalina Hristova in the Johns Hopkins University in Baltimore (USA) we revealed that TrkA and p75 interact directly. But not only that they interact through the transmembrane domain. High quality NMR analysis done by Dr. Konstantin Mineev and Dr. Sergey Goncharuk at Dr. Arseniev laboratory in Moscow, showed a direct interaction between the TMDs of both receptors when reconstituted in lipid micelles. In our lab, Maria Luisa Franco, a PhD student in the lab, was we able to map using site-directed mutagenesis to map the protein interface between both receptors. For that we co-expressed p75 and TrkA full-lenght proteins in HEK293 cells, wt or mutants, and studied the activation of TrkA at increasing concentrations of NGF. Our results found that p75 induced an increase in the activation of TrkA at lower concentrations of NGF, and mutations in the heterodimer interface reduce this activation. In addition we performed those studies, Andrea Soler, a Master Sudent in the Lab, electroporated PC12nnr5 cells /that do not express endogenous TrkA) and found that mutations affecting the interface reduced the differentiation of the PC12nnr5 upon NGF stimulation. Furthermore, FRET analysis done by Taylor Light in Hristova's lab showed in the absence of NGF, TrkA and p75 interact constitutively in the plasma membrane of cells. The most interesting finding shows that upon NGF binding to TrkA there is a conformational change in the complex and a decrease in the FRET between the two receptors are observed. we still do not known what this change implies; a re-arrangement of the complex or that p75 leave the interaction with p75. Further analysis is required.
In summary our work support the data from the last 30 years suggesting a functional interaction between p75 and TrkA, and open the possibility to study at high molecular detail the nature of this fascinating co-receptor complex.
References:
Interaction between the transmembrane domains of neurotrophin receptors p75 and TrkA mediates their reciprocal activation.
Franco ML, Nadezhdin KD, Light TP, Goncharuk SA, Soler-Lopez A, Ahmed F, Mineev KS, Hristova K, Arseniev AS, Vilar M.
J Biol Chem. 2021 Aug;297(2):100926. doi: 10.1016/j.jbc.2021.100926.