Rabbit serum amyloid protein A: expression and primary structure deduced from cDNA sequences

Area of Science:

• Molecular Biology
• Biochemistry
• Immunology

Background:

• Serum amyloid A protein (SAA) is an acute phase apolipoprotein synthesized by hepatocytes.
• SAA is the precursor to amyloid protein A (AA), implicated in secondary amyloidosis.
• Interspecies homology and potential isoform-specific amyloidogenic differences in SAA exist.

Purpose of the Study:

• To analyze the nucleotide and deduced amino acid sequences of two rabbit SAA isoforms (SAA1 and SAA2).
• To investigate the tissue-specific expression and regulation of SAA mRNA in response to inflammatory stimuli in rabbits.

Main Methods:

• Nucleotide sequencing of rabbit SAA cDNA clones.
• Deduction of amino acid sequences and comparison between isoforms.
• Northern blot analysis to detect SAA mRNA expression in various rabbit tissues post-turpentine stimulation.

Main Results:

• Two rabbit SAA cDNA sequences (SAA1 and SAA2) were analyzed, differing at five amino acid positions.
• SAA mRNA was predominantly detected in the liver and spleen 18 hours after turpentine induction.
• A third, larger SAA mRNA species was identified.
• SAA1 and SAA2 mRNA levels were similar in stimulated liver but decreased coordinately with repeated inflammation.

Conclusions:

• Rabbit SAA1 and SAA2 isoforms exhibit distinct primary structures.
• Liver and spleen are the primary sites of SAA mRNA expression during acute inflammation in rabbits.
• Repeated inflammatory stimuli lead to a coordinated decrease in SAA1 and SAA2 mRNA levels.