Related Experiment Video
Updated: Sep 2, 2025

Cell-Free Production of Proteoliposomes for Functional Analysis and Antibody Development Targeting Membrane Proteins
Published on: September 22, 2020
Selective Secretion of KDEL-Bearing Proteins: Mechanisms and Functions
F C Palazzo1, R Sitia1, T Tempio1
1Division of Genetics and Cell Biology Vita-Salute San Raffaele University and IRCCS San Raffaele Scientific Institute, Milan, Italy.
Abstract:
In multicellular organisms, cells must continuously exchange messages with the right meaning, intensity, and duration. Most of these messages are delivered through cognate interactions between membrane and secretory proteins. Their conformational maturation is assisted by a vast array of chaperones and enzymes, ensuring the fidelity of intercellular communication. These folding assistants reside in the early secretory compartment (ESC), a functional unit that encompasses endoplasmic reticulum (ER), intermediate compartment and cis-Golgi. Most soluble ESC residents have C-terminal KDEL-like motifs that prevent their transport beyond the Golgi. However, some accumulate in the ER, while others in downstream stations, implying different recycling rates. Moreover, it is now clear that cells can actively secrete certain ESC residents but not others. This essay discusses the physiology of their differential intracellular distribution, and the mechanisms that may ensure selectivity of release.
More Related Videos
Related Concept Videos
ER Retrieval Pathway
The ER uses many checkpoints to prevent the entry of incorrectly folded or a resident protein as cargo onto a transport vesicle. These mechanisms...
Overview of Secretory Vesicles
Various proteins regulate the aggregation of molecules inside the secretory vesicles. Chromogranins...
Regulation of Nuclear Protein Sorting
Role of ER in the Secretory Pathway
Components of the secretory pathway
About a third of proteins synthesized in the cell are sorted via the secretory route. They shuffle between different compartments in membrane-bound vesicles until they reach their final destination. The main intracellular compartments involved...
Overview of Protein Sorting and Transport
Protein sorting can be of two types: signal-based sorting and vesicle-based trafficking. In signal-based sorting, specific amino acid sequences called sorting signals target proteins to the proper location inside the cell either via gated transport or by protein translocation. In gated transport, folded...
Bacterial Translocation and Protein Secretion

