AN EM AUTORADIOGRAPHY AND IMMUNOFLUORESCENCE STUDY EXAMINING THE PATHWAY OF SERUM AMYLOID A THROUGH THE MACROPHAGE

摘要

Serum amyloid A (SAA) is an evolutionary conserved acute phase protein whose plasma concentration increases 1000-fold during inflammation (1,2). The major biological function of AP-SAA still remains to be elucidated though there is growing evidence that SAA is involved in cholesterol transport (3). In this study we investigated the pathway that HDL/SAA followed through murine peritoneal macrophages to elucidate a putative role for SAA during inflammation. Using both immunofluorescence and EM autoradiography we showed that HLD/SAA was taken up rapidly by macrophages, proceeded through the cytoplasm to the peri-nuclear region, was then observed in the nucleus, later re-emerged to the cytoplasm and the plasma membrane where it was exocytosed into the extracellular environment. Through both of these techniques we were able to demonstrated that SAA has a finite association with macrophages that last approximately 1 hour, which is consistent with the half-life of SAA in the circulation. The observation that SAA is in the nucleus is to the best of our knowledge a novel finding and has implications that SAA may play a role in gene regulation.