Pathways of unconventional protein secretion

Area of Science:

• Cell Biology
• Molecular Biology
• Protein Secretion

Background:

• Most extracellular proteins use the classical endoplasmic reticulum (ER)/Golgi pathway.
• Unconventional protein secretion (UPS) involves proteins lacking signal peptides.
• UPS is independent of brefeldin A, a classical pathway inhibitor.

Purpose of the Study:

• To discuss molecular mechanisms of UPS.
• To focus on fibroblast growth factor 2 (FGF2) translocation across plasma membranes.
• To highlight the role of autophagosomes in acyl-CoA binding protein (ACBP) secretion.

Main Methods:

• Review of literature on unconventional protein secretion.
• Analysis of FGF2 translocation mechanisms.
• Investigation of autophagosome involvement in ACBP secretion.

Main Results:

• Two main UPS types identified: direct plasma membrane translocation (e.g., FGF2) and involvement of intracellular intermediates (e.g., ACBP).
• FGF2 secretion occurs via direct translocation across the plasma membrane.
• ACBP secretion involves intracellular transport intermediates, potentially including autophagosomes.

Conclusions:

• Unconventional protein secretion encompasses diverse mechanisms.
• Direct plasma membrane translocation and autophagosome-mediated pathways are key UPS routes.
• Understanding UPS is crucial for comprehending protein export beyond the classical ER/Golgi pathway.