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Derek McCusker1, Anne Royou, Christophe Velours
1European Institute of Chemistry and Biology, 33607 Pessac, France.
This study explores how Cdk1, a key cell cycle regulator, influences membrane trafficking in yeast. While Cdk1 is known to activate proteins that guide cell growth, the researchers found that Cdk1 inhibition leads to growth defects similar to those seen when actin is disrupted. However, unlike actin disruption, Cdk1 inhibition does not cause a buildup of vesicles inside the cell. Instead, exocytic vesicles are redirected away from the growing bud, possibly to the vacuolar system. Additionally, Cdk1 inhibition disrupts the organization of endocytic and exocytic zones at the growth site. These findings suggest that Cdk1 modulates membrane trafficking dynamics, likely to coordinate cell surface growth with the cell cycle.
Area of Science:
Background:
Polarized cell growth in budding yeast relies on precise coordination of membrane trafficking and cytoskeletal organization. Prior research has shown that Cdk1 activates Rho-family GTPases, which in turn regulate actin cytoskeleton polarization to guide membrane delivery to growth sites. However, the extent of Cdk1's role in membrane trafficking remains unclear. This gap motivated a closer examination of Cdk1's influence beyond its known functions. Established knowledge includes the role of Rho GTPases in actin organization and vesicle targeting. Yet, no prior work had resolved whether Cdk1 directly modulates vesicle dynamics. The secretory pathway's reliance on actin is well-documented, but its interplay with Cdk1 is less understood. This study addresses whether Cdk1 contributes to membrane trafficking beyond GTPase activation. The findings may clarify how cell cycle regulators coordinate growth with trafficking events.
Purpose Of The Study:
The aim of this work is to determine whether Cdk1 has roles in membrane trafficking beyond its activation of Rho-family GTPases. The specific problem involves understanding how Cdk1 inhibition affects polarized growth and vesicle dynamics. The motivation stems from the observation that Cdk1 is essential for growth initiation but its broader trafficking functions remain unexplored. The study tests whether Cdk1 inhibition leads to trafficking defects similar to those caused by actin disruption. The research focuses on whether Cdk1's effects are limited to GTPase activation or extend to vesicle targeting. The goal is to assess the direct role of Cdk1 in membrane trafficking dynamics. The study also examines how Cdk1 inhibition impacts endocytic and exocytic zones. The findings may reveal how Cdk1 coordinates trafficking with growth and cell cycle progression.
Main Methods:
The study uses budding yeast as a model system to investigate Cdk1's role in membrane trafficking. Cdk1 inhibition is achieved through pharmacological agents or genetic manipulation. Membrane trafficking is monitored using fluorescent markers for vesicles and growth sites. Actin depolymerization is used as a control to compare trafficking defects. Post-Golgi vesicle dynamics are tracked to assess targeting accuracy. Endocytic and exocytic zones are analyzed for structural organization. The researchers employ live-cell imaging to observe vesicle behavior in real time. Quantitative analysis includes measuring vesicle accumulation and mistargeting events.
Main Results:
Cdk1 inhibition leads to severe cell surface growth defects, comparable to actin depolymerization. However, unlike actin disruption, Cdk1 inhibition does not cause intracellular vesicle accumulation. Instead, exocytic vesicles are rapidly mistargeted away from the growing bud. The misdirected vesicles appear to be redirected toward the endomembrane or vacuolar system. Endocytic and exocytic zones at the growth site show disorganization after Cdk1 inhibition. These findings suggest that Cdk1 modulates trafficking dynamics beyond GTPase activation. The mistargeting effect is distinct from actin-related trafficking defects. The results indicate that Cdk1 coordinates membrane trafficking with growth progression.
Conclusions:
The authors propose that Cdk1 modulates membrane trafficking dynamics, which is likely important for coordinating growth with the cell cycle. Their findings suggest that Cdk1's role extends beyond activating Rho-family GTPases. The study shows that Cdk1 inhibition causes trafficking defects distinct from actin disruption. The mistargeting of vesicles to endomembrane or vacuolar regions is a novel observation. The disorganization of endocytic and exocytic zones supports this conclusion. The researchers suggest that Cdk1's trafficking effects are essential for growth coordination. These findings may inform future studies on cell cycle-trafficking interactions. The authors do not propose broader implications beyond their stated claims.
Cdk1 inhibition causes vesicle mistargeting and growth defects, distinct from actin disruption effects.
Exocytic vesicles are rapidly redirected away from the growing bud toward endomembrane/vacuolar regions.
To compare trafficking defects caused by Cdk1 inhibition with those from actin disruption.
Cdk1 inhibition disrupts organization of endocytic and exocytic zones at growth sites.
Mistargeting suggests Cdk1 modulates trafficking dynamics to coordinate growth with the cell cycle.
They suggest Cdk1 modulates membrane trafficking dynamics to coordinate growth with cell cycle progression.