A heat shock protein70 fusion protein with alpha(1)-antitrypsin in plasma of Type 1 diabetic subjects

The recent observation that heat shock proteins (HSPs), mostly glucose regulated protein94 (Grp94) and HSP70, are present in plasma of Type 1 diabetic subjects as complexes with immunoglobulins, prompted us to investigate the nature and extent of this association, whether it represents HSP-induced activation of the immune system. Two complementary affinity chromatography procedures followed by immunoprecipitation and immunoblot analyses of HSP-enriched, plasma-purified peaks, revealed that HSPs were inextricably linked with IgG in SDS-resistant complexes from which proteins dissociate partially under reducing treatment. HSP70 was found also closely linked with α1-antitrypsin (α1AT) in a single protein having the mass of α1AT but elution characteristics different from those of normal α1AT. Immunoprecipitation with anti-HSP70 antibodies led to co-immunoprecipitation of the α1AT species linked to HSP70, thus confirming fusion of the proteins. The additional finding of circulating antibodies against the HSP70-α1AT protein supported its immunogenic properties with implications for diabetes and its complications.