Related Experiment Video
Updated: Jul 1, 2026
08:51
The Microscopy-Based Assay to Study and Analyze the Recycling Endosomes using SNARE Trafficking
Published on: February 12, 2022
Rab13 regulates membrane trafficking between TGN and recycling endosomes in polarized epithelial cells
Rita L Nokes1, Ian C Fields, Ruth N Collins
1Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL 60208, USA.
The Journal of Cell Biology
|September 10, 2008
Summary
Rab13 protein regulates membrane trafficking between the trans-Golgi network (TGN) and recycling endosomes (RE). This discovery identifies a key regulator for epithelial cell polarity and protein delivery.
Area of Science:
- Cell Biology
- Molecular Biology
- Membrane Trafficking
Background:
- Epithelial cells maintain polarity by sorting proteins to specific membrane domains.
- Transmembrane protein transport involves pathways from the trans-Golgi network (TGN) through recycling endosomes (RE) to the plasma membrane.
- Proteins regulating the TGN-RE transport step were previously unknown.
Purpose of the Study:
- To identify and characterize proteins involved in regulating membrane trafficking between the TGN and RE.
- To investigate the role of Rab13 in the transport of transmembrane proteins during biosynthetic delivery.
Main Methods:
- Rab13 localization studies using immunofluorescence in epithelial cells.
- Gene silencing (short hairpin RNA) and overexpression of Rab13 alleles in human bronchial epithelial and Madin-Darby canine kidney cells.
- Analysis of protein localization (TGN38/46) and surface delivery of cargo proteins (VSVG, LDLR-CT27).
Main Results:
- Rab13 was found to partially colocalize with TGN38 at the TGN and transferrin receptors in RE.
- Rab13 knockdown or altered expression disrupted TGN38/46 localization at the TGN.
- Rab13 mutants inhibited the surface delivery of proteins utilizing the TGN-RE pathway, but not those using a direct TGN-plasma membrane route.
Conclusions:
- Rab13 plays a crucial role in regulating membrane trafficking between the TGN and RE.
- This function of Rab13 is essential for the proper biosynthetic delivery of specific transmembrane proteins.
- The findings identify Rab13 as a key regulator of the TGN-RE pathway in epithelial cells.
Related Concept Videos
00:58Recycling Endosomes and Transcytosis
The recycling endosome, also known as the endosomal recycling compartment (ERC), is a part of the slow-recycling process of the endocytic pathway. Molecules internalized through receptor-mediated endocytosis are either degraded in the lysosomes or are recycled to the plasma membrane through the fast- or slow-recycling route.
The recycling endosome is not a single organelle but an extensively tubulated network of recycling pathways. It functions in storing molecules or transporting them across...
The recycling endosome is not a single organelle but an extensively tubulated network of recycling pathways. It functions in storing molecules or transporting them across...
01:28The Early Endosome: Endocytosis of Transferrin
Essential proteins such as insulin or low-density lipoprotein (LDL) and micronutrients such as iron enter a eukaryotic cell through receptor-mediated endocytosis. Subsequently, the early endosomes fuse with the vesicles containing such receptor-ligand complexes and play a vital role in sorting the incoming ligands and receptors. While the ligands are either degraded inside the vesicle or released into the cytosol, their receptors are returned to the plasma membrane for further rounds of...
01:45Tail-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...
01:25Rab Cascades
Rab GTPases act in a regulated cascade during membrane fusion, helping the lipid bilayers mix. The Rab family of proteins are active when bound to GTP, and inactive when bound to GDP. Hence, they act as guanine nucleotide-dependent molecular switches. Rab-GTP recognizes and binds to long or short-range tethering proteins to capture the target vesicle. These tethers coordinate with SNAREs on the vesicle and the target membrane to assemble the trans SNARE complex that locks the mixing bilayers.
01:14Rab Proteins
Rab proteins constitute the largest family of monomeric GTPases, of which 70 members are present in humans. Rab proteins and their effectors regulate consecutive stages of vesicle transport such as vesicle transport, docking, and fusion to the correct recipient membrane.
Rab proteins switch between a cytosolic, GDP-bound inactive state and a membrane-anchored, GTP-bound active state. By themselves, Rabs show slow rates of GDP/GTP exchange and GTP hydrolysis. Thus, Rab proteins are considered...
Rab proteins switch between a cytosolic, GDP-bound inactive state and a membrane-anchored, GTP-bound active state. By themselves, Rabs show slow rates of GDP/GTP exchange and GTP hydrolysis. Thus, Rab proteins are considered...
01:45ER 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...
The ER uses many checkpoints to prevent the entry of incorrectly folded or a resident protein as cargo onto a transport vesicle. These mechanisms...