HDAC Inhibitors as Epigenetic Regulators

The C532A-E/A mutant showed higher levels of the monomeric form (Fig. 7B,lane 8). of MT6-MMP to the cell surface, partitioning into lipid rafts or cleavage of -1-proteinase inhibitor. However, monomeric forms of MT6-MMP exhibited enhanced autolysis and metalloprotease-dependent degradation. Collectively, these studies establish the stem region of MT6-MMP as the dimerization interface, an event whose end result imparts protease stability to the protein. The MMP3family of zinc-dependent endopeptidases includes both JNJ 63533054 secreted and membrane-anchored proteases that can hydrolyze multiple substrates at unique cellular and extracellular locations in physiological and pathological conditions (1). The membrane-anchored MMPs, known as membrane type-MMPs (MT-MMPs) developed to specifically target substrates at the pericellular space and in the plasma membrane by incorporating two unique anchoring motifs, namely a transmembrane domain name as in the case of MT1-(MMP14), MT2-(MMP15), MT3-(MMP16), and MT5-MMP (MMP24) or a glycosylphosphatidylinositol (GPI) moiety as in the case of MT4-(MMP17) and MT6-MMP (MMP25) JNJ 63533054 (2). The presence of membrane-anchoring domains confers unique properties and regulatory mechanisms to this subset of MMPs, which serve to tightly control the localization and amount of protease at the cell surface. These regulatory mechanisms include targeting to cell-matrix contacts, insertion into membrane microdomains, internalization and recycling, processing, oligomerization, and ectodomain shedding (3,4). Although there is usually substantial information around the regulation of transmembrane MT-MMPs by these processes, in particular with MT1-MMP (35), JNJ 63533054 little is known about the regulation of GPI-MT-MMPs, MT4- and MT6-MMP. Structurally, the GPI-MT-MMPs comprise the classical domain name business of MMPs including an N-terminal prodomain, a zinc-containing catalytic domain name, a hinge region, and a C-terminal hemopexin-like domain name (68). Like all users of the MT-MMP family, the GPI-MT-MMPs also contain a stem (stalk) region downstream of the hemopexin-like domain name which is followed by the anchoring motif. However, as opposed to the transmembrane MT-MMPs, the stem region of MT6- and MT4-MMP contains three and two unique cysteine residues, respectively, which may play a role in formation of disulfide bridges (8). Recent evidence from our laboratory has shown that under non-reducing conditions MT6-MMP is usually consistently detected as a major form of 120 kDa, likely representing dimeric enzyme complexes at the cell surface (9). Upon reduction, MT6-MMP is mostly found as a 57-kDa species. Based on these data, we hypothesized Mouse monoclonal to CD45.4AA9 reacts with CD45, a 180-220 kDa leukocyte common antigen (LCA). CD45 antigen is expressed at high levels on all hematopoietic cells including T and B lymphocytes, monocytes, granulocytes, NK cells and dendritic cells, but is not expressed on non-hematopoietic cells. CD45 has also been reported to react weakly with mature blood erythrocytes and platelets. CD45 is a protein tyrosine phosphatase receptor that is critically important for T and B cell antigen receptor-mediated activation that this 120-kDa form of MT6-MMP represents enzyme homodimers held by intermolecular disulfide bridges within the stem region (9). In this study we examined the role of the cysteine residues located within the stem region in dimerization of MT6-MMP by site-directed mutagenesis and computational and functional studies. We show that that Cys532is essential for dimer formation. These studies establish a unique role for the stem region of MT6-MMP in mediating disulfide-linked homodimerization. == EXPERIMENTAL PROCEDURES == Cell CultureThe human colon cancer cell collection HCT-116 (CCL-247), the immortalized monkey kidney cell collection COS-1 (CRL-1650), and the human promyelocytic cell collection HL-60 (CCL-240) were all obtained from the American Type Culture Collection (ATCC). HCT-116 and COS-1 cells were cultured in Dulbecco’s altered Eagle’s medium supplemented with 8% fetal calf serum and antibiotics. HL-60 cells were cultured in RPMI 1640 medium (Invitrogen) supplemented with 8% fetal calf serum and antibiotics (100 models/ml penicillin G sodium and 100 g/ml streptomycin sulfate). All cell lines were managed at 37 C in an atmosphere of 95% air flow and 5% CO2. HL-60 DifferentiationHL-60 cells were induced to differentiate into neutrophil-like cells by treatment with dimethyl sulfoxide (DMSO) as explained (10,11). Briefly, HL-60 cells at a density of 1 1.0 106cells/ml were treated with 1.25% DMSO in complete culture media for 7 days. The cells were then harvested, pelleted, and processed for immunoblot analyses as explained below. Differentiation into neutrophil-like cells was monitored by mRNA expression of bcl-2 and bfl-1, as previously explained (12). AntibodiesThe monoclonal antibody (mAb) MAB1142 to human MT6-MMP was purchased from R&D Systems (Minneapolis, MN). A rabbit pAb to human caveolin.