Related Experiment Video

Updated: Apr 4, 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

920

GSK3-mediated raptor phosphorylation supports amino-acid-dependent mTORC1-directed signalling

Clare Stretton1, Thorsten M Hoffmann1, Michael J Munson2

  • 1Division of Cell Signalling & Immunology, James Black Centre, College of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K.

The Biochemical Journal
|September 9, 2015
PubMed

Insights

Inhibiting glycogen synthase kinase-3 (GSK3) reduces amino acid-regulated mTORC1 signaling by affecting raptor phosphorylation. This impacts cellular metabolism, leading to increased autophagy and reduced cell growth.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Mammalian or mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) is a key regulator of cellular metabolism and growth.
  • mTORC1 integrates nutrient and growth factor signals to control these processes.

Purpose of the Study:

  • To investigate the role of glycogen synthase kinase-3 (GSK3) in regulating mTORC1 signaling.
  • To identify the mechanism by which GSK3 influences mTORC1 activity.

Main Methods:

  • Pharmacological inhibition and shRNA-mediated gene silencing of GSK3.
  • Assessment of mTORC1 signaling by measuring phosphorylation of downstream targets.
  • Analysis of raptor phosphorylation at Serine 859 (Ser859).
  • Investigation of mTOR-raptor interaction and substrate phosphorylation.

Main Results:

  • GSK3 suppression significantly reduces amino acid-regulated mTORC1 signaling.
  • GSK3 phosphorylates raptor on Ser859, a key regulatory site.
  • GSK3 inhibition or S859A raptor mutation decreases mTOR-raptor interaction.
  • Reduced mTOR-raptor interaction leads to decreased phosphorylation of p70S6K1 and ULK1, increasing autophagic flux and reducing cell proliferation.

Conclusions:

  • GSK3 is a crucial regulator of amino acid-dependent mTORC1 signaling.
  • GSK3's phosphorylation of raptor at Ser859 is a critical step in mTORC1 activation.
  • Targeting GSK3 offers a potential strategy to modulate mTORC1 activity, autophagy, and cell proliferation.
Keywords:
L-type (leucine) amino acid transporter 1 (LAT1)amino acidautophagygrowthinsulinleucinep70S6K1proliferationsodium-coupled neutral amino acid transporter 2 (SNAT2)transcription factor EB (TFEB)uncoordinated-51-like kinase (ULK1)

More Related Videos

Oligopeptide Competition Assay for Phosphorylation Site Determination09:16

Oligopeptide Competition Assay for Phosphorylation Site Determination

Published on: May 18, 2017

9.0K
Isolation of Primary Mouse Hepatocytes for Nascent Protein Synthesis Analysis by Non-radioactive L-azidohomoalanine Labeling Method08:04

Isolation of Primary Mouse Hepatocytes for Nascent Protein Synthesis Analysis by Non-radioactive L-azidohomoalanine Labeling Method

Published on: October 23, 2018

20.1K

Related Concept Videos

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...
6.4K
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...
5.1K
mTOR Signaling and Cancer Progression03:03

mTOR Signaling and Cancer Progression

1.7K
MAPK Signaling Cascades01:07

MAPK Signaling Cascades

Mitogen-activated protein kinase, or MAPK pathway, activates three sequential kinases to regulate cellular responses such as proliferation, differentiation, survival, and apoptosis. The canonical MAPK pathway starts with a mitogen or growth factor binding to an RTK. The activated RTKs stimulate Ras, which recruits Raf or MAP3 Kinase (MAPKKK), the first kinase of the MAPK signaling cascade. Raf further phosphorylates and activates MEK or MAP2 Kinases (MAPKK), which in turn phosphorylates MAP...
9.3K
Amplifying Signals via Enzymatic Cascade01:22

Amplifying Signals via Enzymatic Cascade

When a ligand binds to a cell-surface receptor, the receptor's intracellular domain changes shape, which may either activate its enzyme function or allow its binding to other molecules. The initial signal is amplified by most signal transduction pathways. This means that a single ligand molecule can activate multiple molecules of a downstream target. Proteins that relay a signal are most commonly phosphorylated at one or more sites, activating or inactivating the protein. Kinases catalyze...
19.5K
The JAK-STAT Signaling Pathway01:20

The JAK-STAT Signaling Pathway

Several cytokine receptors have tightly bound Janus kinase or JAK proteins attached at their cytosolic tail. Small signaling molecules such as cytokines, growth hormones, or prolactins bind to the cytokine receptors and initiate their dimerization. The dimerization brings the cytosolic JAKs together that trans-phosphorylate and activates each other. The activated JAKs now phosphorylate cytosolic tails of the cytokine receptors, which serve as binding sites for adaptor proteins such as  SH2...
14.0K