mTORC1 directly phosphorylates and activates ERα upon estrogen stimulation

Area of Science:

• Oncology
• Molecular Biology
• Cell Signaling

Background:

• Breast cancer is a leading cause of cancer death in women, with 75% of cases being estrogen receptor-α (ERα) positive.
• Endocrine therapy resistance is a major challenge in treating ER-positive breast cancer, often linked to growth factor signaling pathway aberrations.
• Mechanistic target of rapamycin complex 1 (mTORC1) is a critical signaling node in estrogenic pathways.

Purpose of the Study:

• To elucidate the direct molecular link between mTORC1 signaling and estrogen receptor-α (ERα) in breast cancer.
• To investigate the role of mTORC1 in ERα activation and transcriptional activity.
• To provide a rationale for combination therapies involving mTORC1 inhibitors and endocrine agents.

Main Methods:

• Investigated the interaction between ERα and regulatory-associated protein of mTOR (Raptor).
• Assessed the nuclear translocation of Raptor upon estrogen stimulation.
• Identified mTOR as the kinase responsible for ERα phosphorylation at S104/106.

Main Results:

• Estrogen receptor-α (ERα) directly binds to regulatory-associated protein of mTOR (Raptor).
• ERα binding induces Raptor translocation to the nucleus following estrogen stimulation.
• mTOR directly phosphorylates ERα at S104/106, activating ER target gene transcription.

Conclusions:

• A direct mechanistic link between mTORC1 signaling and ERα has been uncovered.
• mTORC1 signaling is implicated in the pathogenesis of ER-positive breast cancer.
• These findings support the use of mTORC1 inhibitors in combination with endocrine therapy for breast cancer treatment.