Elastin

Overview

•  Structure  
  • rich in proline, lysine, glycine
    • unlike collagen, can exist in nonglycosylated forms
  • fibrillin protein binds to tropoelastin to form elastic fibers  
    • Marfan’s disease is caused by a defect in fibrillin 
      • presentation 
        • long extremities including fingers
        • scoliosis
        • myopia and lens dislocations
          • upward (like a martian leaving for outer space)
            • as opposed to a downward dislocation in homocystinuria
        • mitral valve prolapse
        • ↑ for aortic aneurism
• Function
  • is an elastic protein
    • found in tissues where stretch is needed
      • lungs, dermis of the skin, large arteries, elastic ligaments, vocal cords, ligamenta flava of vertebrae
      • desmosine interchain cross linking between lysine residues gives the protein its elastic stretch 
  • degraded by elastase
    • α₁-antitrypsin normally inhibits elastase
      • class of protease inhibitors
      • synthesized in the liver
    • excess elastase activity caused by α₁-antitrypsin (AAT) deficiency
      • absent α₁-globulin peak in serum protein electrophoresis
      • autosomal codominant inheritence
      • presentation
        • panacinar emphysema
          • worsened by smoking
          • early onset
            • smoking without AAT deficiency usually causes centriacinar emphysema
• cirrhosis

Clinical Significance

Disease 

Comments

Marfan syndrome

• Almost exclusively AD
• Mutation in FBN gene
  • encodes fibrillin-1 gene on chromosome 15
• Patients are susceptible to aortic disease, MVP, lens dislocation, scoliosis, pectus deformity, arachnodactyly

α₁-antitrypsin deficiency

• Autosomal codominant inheritence
• α₁-antitrypsin inhibits elastase
• Can lead to panacinar emphysema and hepatic disease