Productionsecretion

Productionsecretion refers to the cellular processes that generate and export biomolecules produced within a cell. In eukaryotic cells, the majority of secreted and membrane proteins follow the conventional secretory pathway. Translation begins in the cytosol with a signal peptide directing ribosomes to the endoplasmic reticulum (ER). Proteins enter the ER lumen, where folding and initial post-translational modifications occur, followed by quality control. Properly folded proteins are packaged into COPII-coated vesicles and transported to the Golgi apparatus, where they undergo further processing, such as glycosylation and sulfation, and sorting for their final destination. From the Golgi, cargo is directed to the plasma membrane via secretory vesicles.

Secretory routes are broadly categorized as constitutive secretion, in which vesicles continually fuse with the plasma membrane to release their contents, and regulated secretion, in which release is triggered by stimuli such as hormones, neurotransmitters, or nutrients. The secretory pathway also delivers membrane proteins and lipids to the cell surface and can route certain proteins to lysosomes for degradation or specialized extracellular release.

Common secreted products include enzymes (lipases, amylases), hormones (insulin), extracellular matrix components (collagens), mucus components, and antibodies. Examples illustrate functional diversity: insulin is stored in secretory granules and released in response to elevated blood glucose; albumin is mainly secreted constitutively by hepatocytes; secreted matrix proteins shape tissue structure.

Defects in productionsecretion can disrupt cellular communication and homeostasis and underpin diseases such as cystic fibrosis, diabetes mellitus type 1 and type 2, and certain glycosylation disorders. Studying these pathways informs drug development and understanding of physiology.