Inducible expression of the α2-macroglobulin signaling receptor in response to antigenic stimulation: A study of second messenger generation

✍ Scribed by Gourab Bhattacharjee; Uma K. Misra; Govind Gawdi; George Cianciolo; Salvatore V. Pizzo

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 213 KB
• Volume: 82
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.1152

✦ Synopsis

Thioglycollate (TG)-elicited murine, peritoneal macrophages express two receptors for activated forms of the proteinase inhibitor a 2 -macroglobulin (a 2 M*) Ð namely, the low density lipoprotein receptor-related protein (LRP) and the a 2 M signaling receptor (a 2 MSR). We now report that resident peritoneal macrophages express only 400AE50 a 2 MSR receptors/cell compared to 5000AE500 receptor/TG-elicited macrophage. By contrast, LRP expression is only 2±2.5-fold greater on elicited cells. The low level of a 2 MSR expression by resident cells is insuf®cient to trigger signal transduction in contrast to TG-elicited cells which when exposed to a 2 M* demonstrate a rapid rise in inositol 1,4,5-trisphosphate and a concomitant increase in cytosolic free Ca 2 . We then studied a variety of preparations injected subcutaneously for their ability to upregulate a 2 MSR. Macroaggregated bovine serum albumin (macroBSA) injection upregulated a 2 MSR and triggered signaling responses by splenic macrophages. Nonaggregated BSA injection alone or in the presence of alum, by contrast, did not alter a 2 MSR expression. Recombivax (hepatitis B antigen adsorbed to alum) injection also upregulated a 2 MSR on splenic macrophages while the alum carrier had no effect. We conclude that macrophage a 2 M* receptors are inducible and their expression may be regulated, in part, by potential antigens.