LIGAND INDUCED CHANGES IN SURFACE TRAFFICKING OF NEUROTROPHIN RECEPTORS: SINGLE MOLCULE LIVE CELL IMAGING STUDIES
The surface movement of tropomyosin receptor kinase A (TrkA) and the low-affinity nerve growth receptor (p75NTR) plays critical role in their functions. Upon ligand binding e.g. TrkA receptor immobilizes and recruits downstream signaling molecules to promote cell survival. Gonadal steroid 17β-estradiol (E2) enhances cell survival, however the effects of E2 on neurotrophin receptor membrane dynamics is unknown. We used genetic labeling of receptor molecules and single molecule live cell imaging to examine the effect of TrkA ligand NGF, p75NT ligand proNGF and E2 on the diffusion properties of TrkA and p75NTR. Compared to vehicle control (0.073; 0.148 (median;IQR)) we have found that membrane diffusion of TrkA decreased after NGF (0.007; 0.024) and E2 (0.023; 0.067) administration, and elevated upon proNGF (0.106; 0.149) treatment. In contrast, compared to vehicle control (0.011; 0.051) administration of NGF (0.013; 0.087) and E2 (0.026; 0.092) increased, while proNGF (0.008; 0.047) decreased surface trafficking of p75NT molecules. These findings show that E2 treatment mimics ligand binding effects of NGF suggesting that E2 fine tunes neurotrophin signaling through influencing their membrane dynamics.