The allograft inflammatory factor-1 in Creutzfeldt-Jakob disease brains

Abstract

The allograft inflammatory factor-1 (AIF-I) is a 17-kDa IFN-γ inducible Ca2+-binding EF-hand protein that is encoded within the HLA class III genomic region and is involved in immune dysfunction and smooth muscle cell activation. We used immunohistochemistry double labelling experiments to analyse the spatial distribution and cell-type-specific localization of AIF-1 in the brains of patients who died as a result of sporadic Creutzfeldt-Jakob disease (CJD) and neuropathologically unaltered controls. Significantly more AIF-1 immunoreactive macrophages/microglial cells and, interestingly, neurones were observed in CJD patients compared to controls. Western blotting confirmed more prominent AIF-1 immunoreactive bands of approximately 50 kDa in four CJD patients compared to three controls. Chaotropic SDS-PAGE of the recombinant AIF-1 resulted in almost complete reduction of the 50 kDa band and mass spectrometry revealed only AIF-1-specific tryptic protein fragments suggesting that trimerized AIF-1 is the predominant form in vivo. Finally, we analysed mechanisms of neuronal AIF-1 induction. Following H2O2 challenge, a model of general cell stress, we observed the gradual induction of AIF-1 and, more interestingly, release to the supernatant of SKNSH neurones. Parallel reverse transcriptase polymerase chain reaction and sequencing was used to confirm AIF-1 mRNA expression.