Related Experiment Video

Updated: May 13, 2026

Intracellular Phosphoflow Cytometry of Acute Myeloid Leukemia Patient-Derived Xenotransplants
07:38

Intracellular Phosphoflow Cytometry of Acute Myeloid Leukemia Patient-Derived Xenotransplants

Published on: June 6, 2025

mTOR inhibits autophagy by controlling ULK1 ubiquitylation, self-association and function through AMBRA1 and TRAF6

Francesca Nazio1, Flavie Strappazzon, Manuela Antonioli

  • 1Dulbecco Telethon Institute at the Department of Biology, University of Rome 'Tor Vergata', 00133 Rome, Italy.

Nature Cell Biology
|March 26, 2013
PubMed

Insights

Autophagy clearance pathways are regulated by the mammalian target of rapamycin (mTOR) pathway. This study reveals a novel positive feedback loop involving AMBRA1 and ULK1, crucial for autophagy.

Area of Science:

  • Cell Biology
  • Molecular Biology

Background:

  • Autophagy is a fundamental cellular process for clearing damaged components.
  • Autophagosome formation is regulated by key protein complexes, including ULK1 and beclin-1-Vps34.
  • The precise cross-talk between these complexes and mTOR signaling remains incompletely understood.

Purpose of the Study:

  • To elucidate the regulatory mechanisms governing autophagy initiation.
  • To investigate the role of AMBRA1 in the mTOR-ULK1 pathway.

Main Methods:

  • Western blotting to assess protein phosphorylation and ubiquitylation.
  • Immunoprecipitation to study protein-protein interactions.
  • Cellular assays to monitor autophagy flux.

Main Results:

  • mTOR phosphorylates and inhibits AMBRA1 under non-autophagic conditions.
  • Upon autophagy induction, AMBRA1 is dephosphorylated and interacts with TRAF6.
  • AMBRA1 facilitates ULK1 ubiquitylation (Lys-63) by TRAF6, promoting ULK1 stabilization and function.
  • A positive regulatory loop between ULK1 and AMBRA1 is identified.

Conclusions:

  • A novel regulatory pathway involving AMBRA1 and ULK1 in autophagy is described.
  • This pathway enhances ULK1 activity through a positive feedback mechanism.
  • Targeting this loop could offer therapeutic strategies for autophagy-related disorders.

Related Concept Videos

mTOR Signaling and Cancer Progression03:03

mTOR Signaling and Cancer Progression

The mammalian target of rapamycin or mTOR protein was discovered in 1994 due to its direct interaction with rapamycin. The protein gets its name from a yeast homolog called TOR. The mTOR protein complex in mammalian cells plays a major role in balancing anabolic processes such as the synthesis of proteins, lipids, and nucleotides and catabolic processes, such as autophagy in response to environmental cues, such as availability of nutrients and growth factors.
The mTOR pathway or the...
mTOR Signaling and Cancer Progression03:03

mTOR Signaling and Cancer Progression

The mammalian target of rapamycin or mTOR protein was discovered in 1994 due to its direct interaction with rapamycin. The protein gets its name from a yeast homolog called TOR. The mTOR protein complex in mammalian cells plays a major role in balancing anabolic processes such as the synthesis of proteins, lipids, and nucleotides and catabolic processes, such as autophagy in response to environmental cues, such as availability of nutrients and growth factors.
The mTOR pathway or the...
PI3K/mTOR/AKT Signaling Pathway01:22

PI3K/mTOR/AKT Signaling Pathway

The mammalian target of rapamycin  (mTOR) is a serine/threonine kinase that regulates growth, proliferation, and cell survival in response to hormones, growth factors, or nutrient availability. This kinase exists in two structurally and functionally distinct forms: mTOR complex 1  (mTORC1) and mTOR complex 2  (mTORC2). The first form (mTORC1) is composed of a rapamycin-sensitive Raptor and proline-rich Akt substrate, PRAS40. In contrast,  mTORC2 consists of a rapamycin-insensitive companion...
Autophagy01:27

Autophagy

Autophagy is a self-digesting process by which a cell protects itself from threats both within and outside the cell, ranging from abnormal proteins to invading bacteria. In this process, obsolete components of the cell and invading microbes are degraded by hydrolytic enzymes active in an acidic environment of the lysosomal lumen.
An autophagic pathway consists of a series of signaling events activated in response to diverse stress and physiological conditions such as food deprivation,...
Receptor Downregulation in MVBs01:15

Receptor Downregulation in MVBs

Multivesicular bodies (MVBs) are mature endosomes that sort ubiquitinated proteins and then fuse with lysosomes to degrade the sorted proteins. Epidermal growth factor (EGF) and its receptor (EGFR) form a complex that can be internalized through endocytosis, sorted into an MVB, and later degraded.
The EGFR can initiate signaling pathways that  lead to cell proliferation, migration, and differentiation. Overexpression of EGFR  stimulates cells to proliferate. Excessive  EGFR activation may...
Autophagic Cell Death01:18

Autophagic Cell Death

Christian de Duve discovered “autophagy,” a process in which cellular components are engulfed by membrane-bound organelles called autophagosomes. The autophagosomes then fuse with lysosomes to digest the enclosed contents. Autophagy is generally activated in cells to prevent cell death. However, cell death is triggered when the damage is beyond repair.
Autophagy and Apoptosis
Autophagy can activate apoptosis. In normal conditions, the autophagy activating protein Beclin-1 and pro-apoptotic...