Related Experiment Video

Updated: Jun 25, 2026

Monitoring eIF4F Assembly by Measuring eIF4E-eIF4G Interaction in Live Cells
08:47

Monitoring eIF4F Assembly by Measuring eIF4E-eIF4G Interaction in Live Cells

Published on: May 1, 2020

Mammalian target of rapamycin complex 1-mediated phosphorylation of eukaryotic initiation factor 4E-binding protein 1

Elaine A Dunlop1, Kayleigh M Dodd, Lyndsey A Seymour

  • 1Institute of Medical Genetics, Cardiff University, Heath Park, Cardiff, Wales, UK.

Cellular Signalling
|March 11, 2009
PubMed

Insights

Investigating the mammalian target of rapamycin (mTOR) pathway, this study reveals how Raptor mutations disrupt mTOR complex 1 (mTORC1) signaling and identifies key domains for substrate recognition and inhibition. This advances understanding of mTORC1 in human diseases.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The mammalian target of rapamycin (mTOR) pathway is crucial in cellular processes and implicated in various human diseases.
  • Detailed understanding of mTOR complex 1 (mTORC1) protein interactions and regulatory mechanisms remains incomplete.

Purpose of the Study:

  • To elucidate the intricate interactions within mTOR complex 1 (mTORC1).
  • To characterize the roles of specific protein domains and motifs in mTORC1 substrate recognition, phosphorylation, and signaling.
  • To investigate the impact of mutations on mTORC1 activity and its response to cellular cues.

Main Methods:

  • Utilized an in vitro mTORC1 kinase assay to probe protein interactions and functions.
  • Employed site-directed mutagenesis to create specific Raptor and mTOR mutants.
  • Assessed in vivo signaling inhibition by mutant proteins and characterized substrate interactions.

Main Results:

  • Identified a Raptor RNC domain crucial for mTORC1 substrate recognition and phosphorylation of 4E-BP1.
  • Demonstrated that specific Raptor mutants can dominantly inhibit mTORC1 signaling pathways.
  • Characterized the roles of 4E-BP1 motifs (TOS and RAIP) in Raptor binding and mTORC1 phosphorylation.
  • Revealed an mTOR region involved in sensing amino acid availability, with specific mutants showing altered nutrient-dependent activation and FKBP38 sensitivity.
  • Showed FKBP38 inhibits certain mTORC1 activations but not all mutants.

Conclusions:

  • The study highlights the utility of in vitro kinase assays for dissecting mTORC1 signaling components.
  • Specific domains within Raptor and mTOR are critical for substrate recognition, signaling, and nutrient sensing.
  • Understanding these molecular mechanisms provides insights into mTORC1-related diseases and potential therapeutic targets.

More Related Videos

Development and Application of Rapamycin-regulated Tyrosine Phosphatases06:56

Development and Application of Rapamycin-regulated Tyrosine Phosphatases

Published on: September 6, 2024

Identification of Protein Interacting Partners Using Tandem Affinity Purification10:02

Identification of Protein Interacting Partners Using Tandem Affinity Purification

Published on: February 25, 2012

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 rapamycin-insensitive companion...
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...
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...
Regulation of the Unfolded Protein Response01:31

Regulation of the Unfolded Protein Response

Inositol-requiring kinase one or IRE1 is the most conserved eukaryotic unfolded protein response (UPR) receptor. It is a type I transmembrane protein kinase receptor with a distinctive site-specific RNase activity. As the binding mechanics of the misfolded proteins with the N-terminal domain of IRE-1 are unclear, three binding models — direct, indirect, and allosteric -- are proposed for receptor activation. Nevertheless, it is known that once a misfolded protein associates with IRE1, it...
Receptor Tyrosine Kinases01:26

Receptor Tyrosine Kinases

Receptor tyrosine kinases or RTKs are membrane-bound receptors that phosphorylate specific tyrosine on protein substrates. RTKs regulate cellular growth, differentiation, survival, and migration. They contain an extracellular ligand binding domain, a transmembrane domain, and a cytosolic tail with intrinsic kinase activity. Several extracellular signaling molecules activate RTKs in one or more ways and relay the signal downstream. Ligands such as platelet-derived growth factor (PDGF) or...
Calmodulin-dependent Signaling01:16

Calmodulin-dependent Signaling

Calmodulin (CaM) is a calcium-binding protein in eukaryotes that controls various calcium-regulated cellular processes. It has four calcium-binding sites that bind calcium to form the calcium-calmodulin ( Ca2+-CaM) complex. GPCR stimulation increases the calcium levels in the cells that bind to CaM and induces a conformational change.
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...