Hey1- and p53-dependent TrkC proapoptotic activity controls neuroblastoma growth

Area of Science:

• Molecular Biology
• Cell Biology
• Cancer Research

Background:

• The neurotrophin-3 (NT-3) receptor, tropomyosin receptor kinase C (TrkC/NTRK3), functions as a dependence receptor, inducing apoptosis in the absence of NT-3.
• This proapoptotic function suggests a tumor suppressor role for TrkC, a classic tyrosine kinase receptor (RTK).

Purpose of the Study:

• To identify interacting partners involved in TrkC-mediated apoptosis.
• To elucidate the molecular mechanisms underlying TrkC's tumor suppressor activity, particularly in neuroblastoma.

Main Methods:

• Investigated direct interactors of the TrkC intracellular domain using biochemical assays.
• Utilized an avian model to study TrkC's tumor suppressor activity in vivo.
• Analyzed the transcriptional regulation of key apoptotic and cell cycle regulatory genes.

Main Results:

• Identified Hey1 (bHLH transcription factor) and importin-α3 (KPNA4) as direct TrkC interactors, with Hey1 being essential for TrkC-induced apoptosis.
• Demonstrated that the TrkC killer-fragment (TrkC-KF) is nuclear-translocated and interacts with Hey1.
• Showed that TrkC-KF and Hey1 silence MDM2 transcription, stabilizing p53.
• p53 upregulates COBRA1 and BAX, initiating the intrinsic apoptosis pathway.
• TrkC's tumor suppressor activity in neuroblastoma models requires both Hey1 and p53.

Conclusions:

• TrkC-mediated apoptosis involves nuclear translocation of TrkC-KF, interaction with Hey1, MDM2 silencing, p53 stabilization, and subsequent activation of the intrinsic apoptosis pathway.
• Hey1 and p53 are critical mediators of TrkC's tumor suppressor function, particularly in neuroblastoma.