collagen type-1

Function

• see collagen
• collagen fibers are a major component of extracellular matrix
• great tensile strength
• gives bone its elasticity & contributes to fracture resistance.
• facilitates formation of bone from cartilage; 40 nm gaps between the ends of the tropocollagen subunits probably serve as nucleation sites for the deposition of long, hard, fine crystals of the mineral component, hydroxyapatite
• end product when tissue heals by repair
• associates with type-5 collagen & type-6 collagen

Structure

• in bone, entire collagen triple helices lie in a parallel, staggered array

Expression

• most abundant collagen of the human body
• skin
• scar tissue
• tendons
• endomysium of myofibrils
• fibrocartilage
• organic part of bone 95% of collagen in bone is type 1
• expression of type 1 procollagen is enhanced by activity of the TGF-beta/Smad/CTGF axis; TGF-beta & CTGF independently stimulate type 1 procollagen expression

Pathology

• defects in type-1 collagen associated with
  • osteogenesis imperfecta
  • Ehlers-Danlos Syndrome
  • also see collagen
• diminished production of type 1 procollagen by fibroblasts occurs with chronological aging of human skin via downregulation of the TGF-beta/Smad/CTGF axis

Notes

Formation of collagen type-1 (most collagens are formed similarly)

• intracellular
  • 3 peptide chains are formed (2 COL2A1 & 1 COL1A2) in ribosomes along the rough endoplasmic reticulum (ER) these peptide chains (preprocollagen); each chain has registration peptides on each end & a signal peptide
  • preprocollagen chains are translocated into the lumen of the ER via N-terminal signal peptides
  • signal Peptides are cleaved inside the RER (procollagen)
  • hydroxylation of Lys & Pro occurs in the ER lumen. process is dependent on ascorbate (vit C) as a cofactor
  • O-glycosylation of specific hydroxy amino acid residues
  • triple helical structure is formed inside the ER
  • procollagen is shipped to the GOLD, where it is packaged & secreted by exocytosis
• extracellular
  • registration peptides are cleaved & tropocollagen is formed by procollagen peptidase
  • multiple tropocollagen molecules form collagen fibrils, & multiple collagen fibrils form into collagen fibers
  • collagen is attached to cell membranes via several types of protein, including fibronectin & integrins

More general terms

• collagen