Unconventional protein secretion

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Unconventional protein secretion (known as ER/Golgi-independent protein secretion or nonclassical protein export

eukaryotes, however an unconventional export mechanism was found in lower eukaryotes too.[3] Even proteins folded in their correct conformation can pass plasma membrane this way, unlike proteins transported via ER/Golgi pathway.[1] Two types of unconventional protein secretion are these: signal-peptid-containing proteins and cytoplasmatic and nuclear proteins that are missing an ER-signal peptide (1).[2]

Signal-peptide-containing proteins

These proteins contain a specific signal-peptide sequence, which is to be translated into the endoplasmic reticulum, but are, however, able to reach the cell surface unconventionally. They can be packed into a COPII-coated vesicle and directly fuse with plasma membrane or can fuse with endosomal or lysosomal compartment. Alternatively, they can be packed into non-COPII-coated vesicle as well and fuse with Golgi (before reaching plasma membrane) or directly delivered to the plasma membrane.[2]

Cytoplasmatic/nuclear secretory proteins

Soluble proteins can reach the surface of the cell both by non-vesicular and vesicular mechanisms. Non-vesicular mechanisms use a carrier to get proteins into extracellular space (for example phosphatidylinositol-4,5-bisphosphate). Vesicular mechanisms can use the

multivesicular bodies.[2]

References

  1. ^
    PMID 15075234
    .
  2. ^
    S2CID 9824754
    .
  3. PMID 20637599
    .
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