Collagen Synthesis and Breakdown Lecture Notes
Overview
- Focus: Synthesis and breakdown of collagen in the body.
- Key Cell: Fibroblasts specialize in synthesizing collagen.
Types of Fibroblasts
- Osteoblasts: Produce type I collagen in bones.
- Chondroblasts: Produce type II collagen in cartilage.
Collagen Synthesis Process
Inside the Cell
- Nucleus:
- Transcription of collagen genes occurs.
- Formation of mRNA molecule.
- Cytosol:
- mRNA exits nucleus and is translated by ribosomes.
- Formation of prepro-alpha-chains.
- Signal sequence peptide directs polypeptides to rough ER.
Rough Endoplasmic Reticulum (RER)
- Translation Continuation:
- Cleavage of signal peptide to form pro-alpha-chains.
- Hydroxylation of proline and lysine to form hydroxyproline and hydroxylysine by hydroxylase enzyme.
- Glycosylation of hydroxylysine with glucose or galactose.
- Pro-collagen Formation:
- Three pro-alpha-chains form pro-collagen held by disulfide bonds at propeptide regions.
Golgi Apparatus
- Formation of vesicles.
- Exocytosis:
- Pro-collagen vesicles released outside the cell.
Outside the Cell
- Peptidases Action:
- Cleave propeptide ends to form collagen monomer.
- Fibril Formation:
- Monomers stack to create fibrils.
- Lysyl oxidase enzyme uses copper to form covalent bonds, stabilizing fibrils.
Collagen Stability Disorders
- Scurvy:
- Vitamin C deficiency affects hydroxylation.
- Unstable collagen leads to symptoms like bleeding.
- Menkes Disease:
- Copper deficiency affects lysyl oxidase.
- Leads to poor collagen cross-linking.
Collagen Breakdown
- Collagenases (Metalloproteases):
- Breakdown collagen in a dynamic process for remodeling.
Next Steps
- Future lectures will cover medical conditions related to collagen synthesis issues.
Note: Collagen synthesis begins within the cell and finalizes outside the cell. The process involves multiple cellular components and enzymatic actions to ensure the collagen structure is robust and functional.