Transcriptional Regulation of CHI3L1, a Marker Gene for Late Stages of Macrophage Differentiation

Abstract

The protein product of the CHI3L1 gene, human cartilage 39-kDa glycoprotein (HC-gp39), is a tissue-restricted, chitin-binding lectin and member of glycosyl hydrolase family 18. In contrast to many other monocyte/macrophage markers, its expression is absent in monocytes and strongly induced during late stages of human macrophage differentiation. To gain insights into the molecular mechanisms underlying its cell typerestricted and maturation-associated expression in macrophages, we initiated a detailed study of the proximal HC-gp39 promoter. Deletion analysis of reporter constructs in macrophage-like THP-1 cells localized a region directing high levels of macrophage-specific reporter gene expression to ϳ300 bp adjacent to the major transcriptional start site. The promoter sequence contained consensus binding sites for several known factors, and specific binding of nuclear PU.1, Sp1, Sp3, USF, AML-1, and C/EBP proteins was detectable in gel shift assays. In vivo footprinting assays with dimethyl sulfate demonstrate that the protection of corresponding sequences was enhanced in macrophages compared with monocytes. Mutational analysis of transcription factor binding sites indicated a predominant role for a single Sp1 binding site in regulating HC-gp39 promoter activity. In addition, gel shift assays using nuclear extracts of monocytes and macrophages demonstrated that the binding of nuclear Sp1, but not Sp3, markedly increases during macrophage differentiation. Our results further highlight the important role of Sp1 in macrophage gene regulation.

Chitinase 3-like 1 expression by human (MG63) osteoblasts in response to lysophosphatidic acid and 1,25-dihydroxyvitamin D3

“…Similar results were obtained for cells cotreated with 1,25D and EGF [34] and 1,25D and colchicine [41]. Herein we now find that During the late stages of human macrophage differentiation, Rehli and colleagues [44] found YKL-40 to be markedly enhanced. In ascertaining the transcriptional regulation of YKL- .…”

“…The models we have utilised are representative of signal transduction "crosscoupling" wherein a pro-mitogenic stimulus, e.g., PMA, converges with a pro-differentiating steroid hormone [51], which, in this particular case, is 1,25D. As with THP-1 cells [44] we now report that PMA and 1,25D synergistically increase YKL-40 production by MG63 cells.…”

“…Although the molecular mechanism by which VDR enhances Sp1-mediated transactivation remains to be resolved it is suggested that the VDR may increase the stability of Sp1-GC rich DNA interaction and resultant stimulation of target genes (which could include YKL-40 and ALP) via an Sp1 transactivation domain. Credence is given to this possibility given that both YKL-40 and ALP genes have Sp1 binding sites in their promoters [44,49].…”

Endogenous HLA–DR–restricted presentation of the cartilage antigens human cartilage gp‐39 and melanoma inhibitory activity in the inflamed rheumatoid joint

“…Consequently, the results would not necessarily correspond. Furthermore, a correlation between levels of antigen in SF and its presentation by SF cells may be lost when the APCs themselves produce the antigen, as has been shown for HC gp-39 in activated macrophages (14)(15)(16)(17)(18), and/or uptake of the antigen by the APCs may not necessarily take place in the SF itself.…”

“…Although the physiologic function of HC gp-39 is still unknown, its expression is specifically induced under pathologic conditions such as RA (8,(11)(12)(13). In RA patients, HC gp-39 is expressed not only by chondrocytes, but also by mature CD16-positive macrophages in the synovium (14) and by peripheral blood-derived macrophages during their differentiation from monocytes (15)(16)(17)(18).…”