apolipoprotein A4 apo-AIV; apoA-IV (APOA4)

Function

• chylomicron-triglyceride transport
• role in chylomicrons & VLDL secretion & catabolism
• required for efficient activation of lipoprotein lipase by apoC2
• potent activator of LCAT
• major component of HDL & chylomicrons
• phosphorylation sites are present in plasma

Structure

• 9 of the 13 22-amino acid tandem repeats are predicted to be highly alpha-helical
  • many of these helices are amphipathic
  • they may serve as lipid-binding domains with LCAT activating activity
  • each22-mer is actually a tandem array of two, A & B, related 11-mers
• belongs to the apolipoprotein A1/A4/E family

Compartment

secreted

Expression

• synthesized primarily in the intestine & secreted probably into lymphatics
• not normally measurable in plasma (present in lymph chylomicrons)

Pathology

• in certain patients with dysbetalipoproteinemia (hyperlipoproteinemia type 3), apo A-IV is found in IDL & LDL

Polymorphism

• 8 alleles have been characterized (APOA-IV*0 to APOA-IV*7)
• APOA-IV*1 is the major allele (90%)
  • APOA-IV*2 is also common (8%)
  • the others are rare alleles

More general terms

• apolipoprotein A
• phosphoprotein

Database

• OMIM: https://mirror.omim.org/entry/107690
• UniProt: http://www.uniprot.org/uniprot/P06727.html
• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=337