[Show abstract][Hide abstract] ABSTRACT: This paper reports the crystallization and preliminary neutron diffraction measurements of HIV-1 protease, a potential target for anti-HIV therapy, complexed with an inhibitor (KNI-272). The aim of this neutron diffraction study is to obtain structural information about the H atoms and to determine the protonation states of the residues within the active site. The crystal was grown to a size of 1.4 mm(3) by repeated macroseeding and a slow-cooling method using a two-liquid system. Neutron diffraction data were collected at room temperature using a BIX-4 diffractometer at the JRR-3 research reactor of the Japan Atomic Energy Agency (JAEA). The data set was integrated and scaled to 2.3 A resolution in space group P2(1)2(1)2, with unit-cell parameters a = 59.5, b = 87.4, c = 46.8 A.
Acta Crystallographica Section F Structural Biology and Crystallization Communications 12/2008; 64(Pt 11):1003-6. DOI:10.1107/S1744309108029679 · 0.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: RME-8 is a DnaJ-domain-containing protein that was first identified in Caenorhabditis elegans as being required for uptake of yolk proteins. RME-8 has also been identified in other species, including flies and mammals, and the phenotypes of their RME-8 mutants suggest the importance of this protein in endocytosis. In the present study, we cloned human RME-8 (hRME-8) and characterized its biochemical properties and functions in endocytic pathways. hRME-8 was found to be a peripheral protein that was tightly associated with the membrane via its N-terminal region. It partially colocalized with several early endosomal markers, but not with late endosomal markers, consistent with observations by immunoelectron microscopy. When cells were transfected with a panel of dominant-active Rab proteins, hRME-8 was confined to large vacuoles induced by expression of Rab5aQ79L, but not by Rab7Q67L. Expression of C-terminally-truncated hRME-8 mutants led to the formation of large puncta and vacuoles, and compromised endocytic pathways through early endosomes, i.e., recycling of transferrin and degradation of epidermal growth factor. Taken together, these results indicate that hRME is primarily involved in membrane trafficking through early endosomes, but not through degradative organelles, such as multivesicular bodies and late endosomes.
Cell Structure and Function 02/2008; 33(1):35-50. DOI:10.1247/csf.07045 · 1.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The C/ebpb gene is translated into three different protein isoforms, two transcriptional activating proteins (38-kDa Full and 34-kDa liver-enriched transcriptional activation protein (LAP)) and one transcriptional inhibitory protein, by alternative use of different AUG initiation codons within the same open reading frame. The isoform 34-kDa LAP is thought to be the most transcriptionally active form of C/EBPbeta in macrophages. To assess the function of the 34-kDa LAP in vivo, we generated knock-in mice, in which methionine 20 of C/EBPbeta, the start site for the 34-kDa LAP is replaced with an alanine. The expression of the 34-kDa LAP was abolished in C/ebpb(M20A/M20A) mice. The induction of C/EBPbeta target genes, such as inflammatory cytokines, chemokines, prostanoid synthetase, and antimicrobial peptides, was abolished in C/ebpb(M20A/M20A) macrophages, and C/ebpb(M20A/M20A) mice were susceptible to Listeria monocytogenes infection. Furthermore, the heat-killed Propionibacterium acnes-induced Th1 response, granuloma formation, and LPS shock were severely impaired. Nevertheless, impairment of intracellular bacteria killing, which is the most prominent phenotype in C/EBPbeta-deficient mice, was not observed in C/ebpb(M20A/M20A) mice. Collectively, we demonstrated that 34-kDa LAP is responsible for NF-IL6-mediated gene induction, but not essential for intracellular bacteria killing in activated macrophages.
The Journal of Immunology 11/2007; 179(8):5378-86. DOI:10.4049/jimmunol.179.8.5378 · 4.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Tom1 (target of Myb 1) protein has VHS and GAT domains in N-terminal and central parts, respectively. The VHS domain has been found in a number of proteins, some of which have been implicated in intracellular trafficking and sorting. We previously showed that Tom1 forms a complex with Tollip, which has been reported to function in interleukin-1 (IL-1)-dependent signaling. In this study, we carried out a reporter gene assay to investigate the function of Tom1 in inflammatory cytokine-dependent signaling. It was found that overexpression of Tom1 suppresses activation of transcription factors, NF-kappaB and AP-1, induced by either IL-1beta or tumor necrosis factor (TNF)-alpha and that the VHS domain of Tom1 is indispensable for its suppressive activity. Thus, we propose that Tom1 is a common negative regulator of the signaling pathways induced by IL-1beta and TNF-alpha.
[Show abstract][Hide abstract] ABSTRACT: The gene for Tom1 was initially identified as a specific target of the oncogene v-myb. The Tom1 protein belongs to the VHS domain-containing protein family, and it has a GAT domain in a central part as well as an N-terminal VHS domain. VHS domain-containing proteins, including Hrs/Vps27, STAM, and GGA proteins, have been implicated in intracellular trafficking and sorting, but the role of Tom1 has not yet been elucidated. In this study, we found that Tom1 binds directly with ubiquitin chains and Tollip, which was initially isolated as a mediator of interleukin-1 signaling and has a capacity to bind ubiquitin chains. Gel filtration and subsequent Western blot analysis showed that endogenous Tom1 associates with Tollip to form a complex. In addition, Tom1 was found to be capable of binding to clathrin heavy chain through a typical clathrin-binding motif. Fluorescence microscopic analysis revealed that green fluorescent protein-Tom1 was localized predominantly in the cytoplasm, whereas its mutant with deletion of the clathrin-binding motif had a diffuse localization throughout the cell. Thus, we propose that a Tom1-Tollip complex functions as a factor that links polyubiquitinated proteins to clathrin.