GRAF2, WDR44, and MICAL1 mediate Rab8/10/11-dependent export of E-cadherin, MMP14, and CFTR ΔF508
Safa Lucken-Ardjomande Häsler1, Yvonne Vallis1, Mathias Pasche1
1Medical Research Council Laboratory of Molecular Biology, Cambridge, UK.
The Journal of Cell Biology
|April 29, 2020
Summary
This study reveals that GRAF proteins, alongside MICAL1 and WDR44, mediate alternative exocytosis pathways. These proteins are crucial for exporting specific transmembrane proteins via Rab8, Rab10, and Rab11-dependent routes.
Area of Science:
- Cell biology
- Molecular biology
- Membrane trafficking
Background:
- Transmembrane proteins utilize classical and alternative secretion pathways.
- Endosomal sorting and Rab GTPase-dependent pathways are key for alternative secretion.
Purpose of the Study:
- To investigate the role of GRAF proteins, MICAL1, and WDR44 in alternative exocytosis.
- To elucidate the involvement of Rab8, Rab10, and Rab11 in these pathways.
Main Methods:
- Immunofluorescence microscopy to assess protein colocalization.
- Co-immunoprecipitation to identify protein-protein interactions.
- Analysis of protein export upon overexpression of dominant-negative mutants.
Main Results:
- GRAF1b/2 extensively colocalize with Rab8a/b and partially with Rab10.
- MICAL1 links GRAF1b/2 to Rab8a/b and Rab10; WDR44 binds Rab11.
- GRAF2 and WDR44 are essential for the export of E-cadherin, MMP14, and CFTR ΔF508.
Conclusions:
- GRAF proteins, MICAL1, and WDR44 are critical components of alternative exocytic routes.
- These proteins facilitate the Rab8/10/11-dependent export of specific transmembrane proteins.
- Understanding these pathways is vital for various biological processes and diseases.
Related Concept Videos
Rab Cascades
3.3K
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.
3.3K
Rab Proteins
4.8K
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...
4.8K
Export of Misfolded Proteins out of the ER
4.8K
After folding, the ER assesses the quality of secretory and membrane proteins. The correctly folded proteins are cleared by the calnexin cycle for transport to their final destination, while misfolded proteins are held back in the ER lumen. The ER chaperones attempt to unfold and refold the misfolded proteins but sometimes fail to achieve the correct native conformation. Such terminally misfolded proteins are then exported to the cytosol by ER-associated degradation or ERAD pathway for...
4.8K
Receptor Downregulation in MVBs
2.7K
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...
The EGFR can initiate signaling pathways that lead to cell proliferation, migration, and differentiation. Overexpression of EGFR stimulates cells to proliferate. Excessive EGFR...
2.7K
Pinching-off of Coated Vesicles
3.9K
Vesicle budding is orchestrated by distinct cytosolic proteins such as adaptor proteins, coat proteins, and GTPases. To initiate vesicle budding, membrane-bending proteins containing crescent-shaped BAR domains bind to the lipid heads in the bilayer and distort the membrane to form a protein-coated vesicle bud. Adaptors proteins such as AP2 for clathrin-coated vesicles can nucleate on the deformed membrane. Finally, coat proteins such as clathrin or COPI and COPII assemble into a coat forming...
3.9K
SNAREs and Membrane Fusion
12.1K
Once a transport vesicle has recognized its target organelle, the vesicular membrane needs to fuse with the target membrane to unload the cargo. Transmembrane proteins called SNAREs present on organelle membranes and their vesicles, mediate vesicle fusion.
SNAREs exist in pairs that symmetrically interact and catalyze the fusion of the lipid bilayers in vesicle and target organelle. v-SNARE in the vesicle membrane are single polypeptide chains that bind to a complementary t-SNARE, composed of 2...
SNAREs exist in pairs that symmetrically interact and catalyze the fusion of the lipid bilayers in vesicle and target organelle. v-SNARE in the vesicle membrane are single polypeptide chains that bind to a complementary t-SNARE, composed of 2...
12.1K


