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Related Concept Videos

Exocytosis00:50

Exocytosis

Exocytosis is a process that releases molecules outside the cell. Like other bulk transport mechanisms, exocytosis requires energy.
Exocytosis is the opposite of endocytosis, which brings molecules inside the cell. Sometimes, the released materials are signaling molecules. For example, neurons typically use exocytosis to release neurotransmitters. Cells also use exocytosis to insert proteins such as ion channels into their cell membranes, secrete proteins for use in the extracellular matrix, or...
Exocytosis00:51

Exocytosis

Exocytosis is used to release material from cells. Like other bulk transport mechanisms, exocytosis requires energy.
Phosphorylation01:02

Phosphorylation

The addition or removal of phosphate groups from proteins is the most common chemical modification that regulates cellular processes. These modifications can affect the structure, activity, stability, and localization of proteins within cells as well as their interactions with other proteins.
During phosphorylation, protein kinases transfer the terminal phosphate group of ATP to specific amino acid side chains of substrate proteins. Serine, threonine, and tyrosine are the most commonly...
Phosphorylation01:02

Phosphorylation

The addition or removal of phosphate groups from proteins is the most common chemical modification that regulates cellular processes. These modifications can affect the structure, activity, stability, and localization of proteins within cells as well as their interactions with other proteins.
During phosphorylation, protein kinases transfer the terminal phosphate group of ATP to specific amino acid side chains of substrate proteins. Serine, threonine, and tyrosine are the most commonly...
Protein Kinases and Phosphatases02:54

Protein Kinases and Phosphatases

Proteins undergo chemical modifications that trigger changes in the charge, structure, and conformation of the proteins. Phosphorylation, acetylation, glycosylation, nitrosylation, ubiquitination, lipidation, methylation, and proteolysis are various protein modifications that regulate protein activity. Such modifications are usually enzyme-driven.
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
Regulated Protein Degradation02:58

Regulated Protein Degradation

It is vital to regulate the activity of enzymatic as well as non-enzymatic proteins inside the cell. This can be achieved either through creating a balance between their rate of synthesis and degradation or regulating the intrinsic activity of the protein. Both these regulation mechanisms play an essential role in the normal functioning of cells.
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...

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Related Experiment Video

Updated: Jun 2, 2026

Automated Detection and Analysis of Exocytosis
13:28

Automated Detection and Analysis of Exocytosis

Published on: September 11, 2021

Exocyst function is regulated by effector phosphorylation.

Xiao-Wei Chen1, Dara Leto, Junyu Xiao

  • 1Life Sciences Institute, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA.

Nature Cell Biology
|April 26, 2011
PubMed
Summary
This summary is machine-generated.

The exocyst complex uses Sec5 phosphorylation to regulate vesicle fusion. This mechanism controls insulin-stimulated Glut4 exocytosis and other cellular trafficking processes.

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Area of Science:

  • Cell Biology
  • Molecular Biology
  • Protein Interactions

Background:

  • The exocyst complex is crucial for tethering vesicles at fusion sites.
  • Small GTPases, like RalA, interact with the exocyst to regulate vesicle trafficking.
  • RalA on Glut4 vesicles binds the exocyst upon insulin activation but must disengage for exocytosis.

Purpose of the Study:

  • To investigate the mechanism of RalA disengagement from the exocyst.
  • To identify the molecular players and processes involved in regulating exocyst-G protein interactions.

Main Methods:

  • Investigated the role of Sec5 phosphorylation in RalA-exocyst interaction.
  • Utilized protein kinase C and phosphatase assays.
  • Employed site-directed mutagenesis of Sec5 phosphorylation sites.
  • Assessed the impact of Sec5 mutations on insulin-stimulated Glut4 exocytosis in cell culture and zebrafish embryos.

Main Results:

  • RalA disengagement from the exocyst is mediated by Sec5 phosphorylation, not RalA inactivation.
  • Phosphorylation occurs in the G-protein binding domain of Sec5, allosterically reducing RalA interaction.
  • Protein kinase C catalyzes Sec5 phosphorylation, reversed by an exocyst-associated phosphatase.
  • Sec5 phosphorylation site mutations disrupt insulin-stimulated Glut4 exocytosis and other cellular trafficking.

Conclusions:

  • The exocyst acts as a gatekeeper for exocytic vesicles.
  • A regulatory circuit of engagement, disengagement, and re-engagement with G proteins controls vesicle trafficking.
  • Sec5 phosphorylation is a key regulatory step in exocytosis and cellular transport.