Related Experiment Video
Updated: Aug 11, 2026
11:33
Monitoring the Assembly of a Secreted Bacterial Virulence Factor Using Site-specific Crosslinking
Published on: December 17, 2013
The polarity-establishment component Bem1p interacts with the exocyst complex through the Sec15p subunit
Y Ellen France1, Charles Boyd, Jeff Coleman
1Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520, USA.
Journal of Cell Science
|February 16, 2006
Summary
Sec15p, an exocyst complex subunit, physically interacts with Bem1p, crucial for cell polarity establishment in yeast. This interaction guides Sec15p localization during bud growth, integrating secretory and polarity pathways.
Area of Science:
- Cell Biology
- Molecular Biology
- Yeast Genetics
Background:
- Polarized bud growth in Saccharomyces cerevisiae relies on precise spatial regulation of the secretory machinery.
- The intricate mechanisms of cross-talk between secretory and cell-polarity pathways remain incompletely understood.
Purpose of the Study:
- To investigate the role of Sec15p, an exocyst complex subunit, in mediating communication between the secretory and cell-polarity establishment machineries.
- To elucidate the functional significance of the interaction between Sec15p and Bem1p in yeast polarized growth.
Main Methods:
- Demonstration of direct physical interaction between Sec15p and Bem1p using biochemical assays.
- Analysis of the localization of green fluorescent protein (GFP)-tagged Sec15 in yeast cells with compromised Sec15p-Bem1p interaction.
- Examination of Sec15-1p, a mutant defective in Bem1p binding, and its localization patterns.
Main Results:
- A direct physical interaction between Sec15p and Bem1p was confirmed, linking the exocyst complex to the Cdc42p-mediated polarity pathway.
- Compromised Sec15p-Bem1p interaction, particularly in cells lacking Bem1p's N-terminal SH3 domain, disrupted Sec15p localization during early bud growth.
- Sec15-1p, unable to bind Bem1p, exhibited mislocalization along with the exocyst subunit Sec8p.
Conclusions:
- The interaction between Sec15p and Bem1p is vital for proper Sec15p localization during the early stages of bud development in yeast.
- Sec15p acts as a crucial integrator of signals between the Rab protein Sec4p and early polarity establishment factors via its interaction with Bem1p.
- This integration facilitates the coordination of the secretory pathway with polarized bud growth, ensuring accurate cell morphogenesis.
Related Concept Videos
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...
01:33Coat Assembly and GTPases
Vesicles incorporate different coat protein subunits in different cell locations, which changes the properties of the coat, such as the shape and geometry of the transport vesicles. Thus, vesicle coat proteins also play a significant role in cargo selection.
Coat assembly depends on the local availability of phosphatidylinositol phosphates or PIPs and GTP-binding proteins. Adaptor proteins, which link the coat proteins to the membrane, bind to these PIPs and play a crucial role in controlling...
Coat assembly depends on the local availability of phosphatidylinositol phosphates or PIPs and GTP-binding proteins. Adaptor proteins, which link the coat proteins to the membrane, bind to these PIPs and play a crucial role in controlling...
01:28Protein Translocation Machinery on the ER Membrane
The translocon complex situated on the ER membrane is the main gateway for the protein secretory pathway. It facilitates the transport of nascent peptides into the ER lumen and their insertion into the ER membrane.
Sec61 protein conducting channel
In eukaryotes, the translocon complex comprises a core heterotrimeric translocator channel called the Sec61 complex. This channel includes three transmembrane proteins, Sec61α, Sec61β, and Sec61γ, and is the largest subunit of the translocon complex.
Sec61 protein conducting channel
In eukaryotes, the translocon complex comprises a core heterotrimeric translocator channel called the Sec61 complex. This channel includes three transmembrane proteins, Sec61α, Sec61β, and Sec61γ, and is the largest subunit of the translocon complex.
01:21Cell Polarization by Rho Proteins
Cell polarity is the asymmetric distribution of cellular and membrane components, making one side of the cell different from the other. This polarity is essential to many processes such as embryogenesis, axon migration, glucose transport across epithelial cells, and directional cell migration. A migrating cell responds to intracellular or extracellular signals via molecular cascades that reorganize the actin cytoskeleton to establish this polarity. In these cells, the Rho family proteins Cdc42,...
01:38Intralumenal Vesicles and Multivesicular Bodies
Intraluminal vesicles (ILVs) are small vesicles 50-80 nm in diameter formed during the maturation of early endosomes. A specialized endosome containing numerous ILVs is called a multivesicular body (MVB). ILVs contain internalized molecules such as antigens, nucleic acids, proteins, and metabolites. Some of these molecules are released from the MVBs inside exosomes and are transported to other cells. Other MVBs contain molecules that are retained in the ILVs and are later degraded within the...
01:32Pinching-off of Coated Vesicles
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...