Macrophage-restricted and Interferon γ-inducible Expression of the Allograft Inflammatory Factor-1 Gene Requires Pu.1

Abstract

Expression of allograft inflammatory factor-1 (Aif-1), a 17-kDa protein bearing an EF-hand Ca 2؉ binding motif, increases markedly in monocytes and macrophages participating in allo-and autoimmune reactions, including the perivascular inflammation in transplanted hearts, microglial infiltrates in experimental autoimmune neuritis, and the inflamed pancreas of prediabetic BB rats. To investigate the mechanism of this regulation, we isolated the mouse aif-1 gene and determined its genomic organization. The gene has six exons distributed over 1.6 kilobases, an interferon ␥-inducible DNase I-hypersensitive site near ؊900, and flanking sequences on either side predicted to associate with nuclear matrix. Reporter gene analyses identified sequences between ؊902 and ؊789, including consensus Ets and interferon regulatory factor elements, required for macrophagespecific and interferon ␥-inducible transcriptional activity. Pu.1 bound to the Ets site in electromobility shift assay and forced expression of Pu.1 activated the aif-1 promoter in 3T3 fibroblasts, in which it is normally inactive. However, the transcriptional activity of a concatamer of the Ets site alone did not increase with interferon ␥ treatment. Cooperation between Pu.1 and proteins binding to the interferon regulatory factor element appears to be necessary for both macrophagespecific and interferon ␥-inducible expression of the aif-1 gene.Allograft inflammatory factor-1 (Aif-1) 1 is a 17-kDa protein first described in differential mRNA display analysis of chronically rejecting transplanted rat hearts (1, 2). The Aif-1 protein was identified in infiltrating mononuclear cells in the allografted hearts, and Western blotting indicated its expression in bone marrow-derived macrophages but not T cells. Gene products with a high level of similarity to Aif-1 have been identified in several other model systems and have been reported with the alternative names Iba1 (3), daintain (5), and Mrf-1 (4). Despite the different screening approaches and systems employed in each case, the cells expressing the aif-1 gene product have been derivatives of the monocyte/macrophage lineage; iba1 was reported from differential mRNA display analysis of brain cell cultures, with induction in microglial cells cultured for extended periods of time (3); daintain was identified because of its effects on insulin release and found to localize to microglia in the central nervous system, and macrophages and dendritic cells in other organs (5); and mrf-1, identified in a differential hybridization screen of cerebellar cultures, localized to OX-42-positive microglia in brain sections, with increased expression in activated microglia surrounding injured central motor neurons (4).The cDNA sequences described in these reports are quite similar but show some variability at the 5Ј end. aif-1 and iba1 sequences diverge at the 5Ј end, consistent with alternative transcription start sites from the same gene (4), but are practically identical downstream of aif-1 base 96 (iba1 base 279). The sequence of d...

Allograft inflammatory factor-1/Ionized calcium-binding adapter molecule 1 is specifically expressed by most subpopulations of macrophages and spermatids in testis

“…As has become clear (Imai and Kohsaka 2002;Deininger et al 2002;Sibinga et al 2002), the Iba1 gene and protein, first mentioned in 1996 (Imai et al 1996), were originally discovered by several groups and independently named Iba1, microglial response factor-1 (MRF-1; Tanaka et al 1998), daintain (Chen et al 1997), and allograft inflammatory factor-1 (AIF-1; Utans et al 1995). Whereas studies of Iba1 and MRF-1 focused on their role in the brain and spinal cord, AIF-1 was first identified as a protein upregulated in cardiac allografts undergoing rejection (Utans et al 1995).…”

Allograft Inflammatory Factor-1 is Up-regulated in Warm and Cold Ischemia-Reperfusion Injury in Rat Liver and May be Inhibited by FK506

“…Also, some previous studies have demonstrated that AIF-1 plays a role in the inflammatory pathway of macrophages and lymphocytes [18][19][20][21]. In human coronary artery disease, AIF-1 is expressed in CD3-positive lymphocytes, and overexpression of AIF-1 enhances activation of lymphocytes, which suggests that AIF-1 plays a role in T-lymphocyte activation [21].…”

AIF1 Gene RS2269475:C>T Polymorphism is Associated With Rheumatoid Arthritis Development but not With Disease Activity

“…In vitro experiments showed that interferon gamma could up-regulate the expression of AIF-1 in macrophages. 15 Moreover, it was shown that macrophage cell line expressed a certain level of endogenous AIF-1 which could be enhanced by pro-inflammatory cytokines IL-1b or tumor necrosis factor-alpha. Macrophages stimulated with AIF-1 produced significantly increased amounts of IL-6, IL-10 and IL-12.…”