Proteins destined for secretion are released from a cell through a regulated process involving transport vesicles and the plasma membrane.
Protein Secretion Pathway
Here's a breakdown of the protein secretion pathway, based on the provided reference:
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Sorting in the Trans-Golgi Network (TGN): Proteins synthesized for secretion are sorted in the TGN. This sorting determines which pathway they will take for release.
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Vesicle Formation: Two types of vesicles are involved:
- Constitutive Secretory Pathway (CSP): Proteins are sorted into vesicles that are nonclathrin-coated.
- Regulated Secretory Pathway (RSP): Proteins are sorted into vesicles that are clathrin-coated.
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Vesicle Trafficking: The secretory vesicles then move towards the plasma membrane.
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Release at the Plasma Membrane: Finally, the vesicles fuse with the plasma membrane, releasing their protein content in a regulated manner. This release is triggered by specific signals depending on the cell type and the protein being secreted.
Table Summarizing Protein Secretion
Step | Description | Vesicle Type | Coating Protein |
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Sorting in TGN | Proteins destined for secretion are sorted into different pathways based on their final destination and regulatory requirements. | CSP (Constitutive), RSP (Regulated) | N/A |
Vesicle Formation | Proteins are packaged into secretory vesicles. | CSP, RSP | Nonclathrin, Clathrin respectively |
Vesicle Trafficking | Vesicles move towards the plasma membrane. | CSP, RSP | N/A |
Release at Plasma Membrane | Vesicles fuse with the plasma membrane, releasing their protein cargo. This process is regulated, especially in the RSP, and often triggered by specific signals. | CSP, RSP | N/A |