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Related Concept Videos

Directing Proteins to the Rough Endoplasmic Reticulum01:34

Directing Proteins to the Rough Endoplasmic Reticulum

The organelle-specific signaling sequences direct proteins synthesized in the cytosol to their final destination like ER, mitochondria, peroxisomes, etc. Some of the proteins directed to ER are then trafficked via vesicles to other organelles within the cell or the extracellular environment through the Golgi complex. For example, the rough ER synthesizes soluble proteins for transportation to the lysosomes or secretion out of the cell. It can also synthesize transmembrane proteins that can...
Insertion of Single-pass Transmembrane Proteins in the RER01:26

Insertion of Single-pass Transmembrane Proteins in the RER

Integral membrane proteins are proteins adhered to the lipid bilayer of a cell organelle or membrane. They can be of two types: transmembrane integral proteins that span the lipid bilayer and monotopic proteins that are attached to either side of the membrane but do not pass through it.
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
Tail-anchoring of Proteins in the ER Membrane01:45

Tail-anchoring of Proteins in the ER Membrane

Tail-anchored, or TA, proteins are estimated to make up to 3-5% of membrane proteins found in the eukaryotic cell. Such proteins have a single transmembrane domain located approximately 30 amino acid residues upstream from the C-terminal end. As a result, the signal recognition particle (SRP) cannot guide a TA protein to the ER membrane for cotranslational insertion. Hence, they are integrated into the ER membrane post-translationally using their C-terminal end as the anchor. TA proteins...
Post-translational Translocation of Proteins to the RER01:27

Post-translational Translocation of Proteins to the RER

A sizable fraction of proteins destined for ER are first synthesized in the cell cytosol and then transported across the ER membrane–a process called post-translational translocation. Similar to cotranslationally translocated proteins, these proteins also use the Sec translocon complex to enter the ER lumen.
Targeting proteins to the ER
Hsp40 and Hsp70 chaperone molecules bind the translated proteins in the cytosol to prevent their folding. The chaperone binding helps to keep the signal...
ER Retrieval Pathway01:45

ER Retrieval Pathway

In the secretory pathway, vesicles transport proteins from one cellular compartment to another in forward transport to deliver the protein to its correct location. Occasionally, misfolded proteins and incorrect proteins escape their original compartments, and a retrieval pathway is used to return the escaped proteins to their original compartment.
The ER uses many checkpoints to prevent the entry of incorrectly folded or a resident protein as cargo onto a transport vesicle. These mechanisms...
Protein Modifications in the RER01:26

Protein Modifications in the RER

Modification of secretory and transmembrane proteins entering the rough ER begins in the ER lumen. These modifications aid in protein folding and stabilize the acquired tertiary structure. Protein modifications in the rough ER co-occur at different stages of protein folding.
Broadly, these modifications can be categorized into four main categories — glycosylation, formation of disulfide bonds, assembly of protein subunits, and specific proteolytic cleavages like removal of signal sequences.

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Visualization of Endoplasmic Reticulum Localized mRNAs in Mammalian Cells
10:24

Visualization of Endoplasmic Reticulum Localized mRNAs in Mammalian Cells

Published on: December 17, 2012

AGR2 gene function requires a unique endoplasmic reticulum localization motif.

Aparna Gupta1, Aiwen Dong, Anson W Lowe

  • 1Department of Medicine and the Stanford Digestive Disease Center, Stanford University, Stanford, California 94305, USA.

The Journal of Biological Chemistry
|December 21, 2011
PubMed
Summary

The carboxyl-terminal KTEL motif is essential for AGR2 protein function in human adenocarcinomas. Specific ER localization signals, like KTEL, are crucial for AGR2

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Published on: February 21, 2019

Area of Science:

  • Molecular and Cellular Biology
  • Cancer Biology
  • Protein Trafficking

Background:

  • Soluble proteins are localized to the endoplasmic reticulum (ER) via retrograde transport mediated by KDEL receptors.
  • While KDEL and its variants can bind KDEL receptors for ER localization, their functional implications remain unclear.
  • AGR2, a protein overexpressed in human adenocarcinomas, promotes tumor growth and transformation.

Purpose of the Study:

  • To determine if AGR2 requires a specific ER localization signal for its functional activity.
  • To investigate the role of the carboxyl-terminal motif in AGR2's function and localization.

Main Methods:

  • Utilized two distinct cell lines engineered to express AGR2.
  • Investigated AGR2's function by assessing the induction of downstream targets: amphiregulin (EGFR ligand) and CDX2 (transcription factor).
  • Manipulated the carboxyl-terminal motif of AGR2 (wild-type KTEL, deleted KTEL, KDEL, KSEL) to assess localization and function.

Main Results:

  • Only the wild-type carboxyl-terminal KTEL motif enabled AGR2 to induce amphiregulin or CDX2 expression.
  • Deletion of the KTEL motif led to AGR2 secretion and loss of function.
  • ER localization with KDEL or KSEL motifs, instead of KTEL, also resulted in loss of AGR2 function.

Conclusions:

  • Variations in ER localization sequences have specific functional implications.
  • The KTEL motif is specifically required for AGR2's function in promoting tumor growth and the transformed phenotype.
  • AGR2's oncogenic activity is dependent on its precise ER localization signal, highlighting the importance of the KTEL motif.