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Related Concept Videos

Small GTPases - Ras and Rho01:24

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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,...
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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.
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Rab Proteins01:14

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The Ras-gene-encoded proteins are regulators of signaling pathways controlling cell proliferation, differentiation, or cell survival. The Ras-gene family in humans constitutes three primary members—the HRas, NRas, and KRas. These genes code for four functionally distinct yet closely related proteins—the HRas, NRas, KRas4A, and KRas4B. The involvement of mutant Ras genes in human cancer was first discovered in 1982 and is among the most common causes of human tumorigenesis.
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Related Experiment Video

Updated: Apr 12, 2026

Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells
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Rap1 Spatially Controls ArhGAP29 To Inhibit Rho Signaling during Endothelial Barrier Regulation.

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The small GTPase Rap1 regulates cell shape and barrier function by controlling Rho signaling. Rap1 induces protein complex formation at the cell membrane, inhibiting Rho and enhancing endothelial barrier function.

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Area of Science:

  • Cell Biology
  • Molecular Signaling
  • Cytoskeletal Regulation

Background:

  • The small GTPase Rap1 is a key regulator of the actin cytoskeleton.
  • Rap1 influences cellular processes like epithelial cell spreading and endothelial barrier function by modulating Rho GTPase signaling.
  • Radil, Rasip1, and ArhGAP29 are identified Rap1 effectors involved in Rho signaling inhibition.

Purpose of the Study:

  • To elucidate the molecular mechanism by which Rap1 inhibits Rho signaling.
  • To investigate the role of Rasip1 and the Radil-ArhGAP29 complex in Rap1-mediated signaling.
  • To understand the spatiotemporal control of Rho signaling through protein complex formation at the plasma membrane.

Main Methods:

  • Investigating protein translocation to the plasma membrane induced by Rap1.
  • Analyzing the formation of multimeric protein complexes.
  • Studying the functional consequences on Rho signaling and endothelial barrier function.

Main Results:

  • Rap1 induces independent translocation of Rasip1 and a Radil-ArhGAP29 complex to the plasma membrane.
  • Formation of a multimeric protein complex is essential for Rap1-induced Rho signaling inhibition.
  • This mechanism leads to increased endothelial barrier function.
  • Findings complement previous work on Epac1, revealing a pathway of successive protein translocations and complex formation.

Conclusions:

  • Rap1 controls Rho signaling and endothelial barrier function via sequential protein translocations and plasma membrane complex assembly.
  • This study reveals a novel signaling pathway for spatiotemporal regulation of Rho GTPase activity.
  • The findings contribute to understanding the molecular basis of cytoskeletal control and cell-cell adhesion.