Nakajo-Nishimura syndrome (NNS) is a disorder that segregates in an autosomal recessive fashion. Symptoms include periodic fever, skin rash, partial lipomuscular atrophy, and joint contracture. Here, we report a mutation in the human proteasome subunit beta type 8 gene (PSMB8) that encodes the immunoproteasome subunit β5i in patients with NNS. This G201V mutation disrupts the β-sheet structure, protrudes from the loop that interfaces with the β4 subunit, and is in close proximity to the catalytic threonine residue. The β5i mutant is not efficiently incorporated during immunoproteasome biogenesis, resulting in reduced proteasome activity and accumulation of ubiquitinated and oxidized proteins within cells expressing immunoproteasomes. As a result, the level of interleukin (IL)-6 and IFN-γ inducible protein (IP)-10 in patient sera is markedly increased. Nuclear phosphorylated p38 and the secretion of IL-6 are increased in patient cells both in vitro and in vivo, which may account for the inflammatory response and periodic fever observed in these patients. These results show that a mutation within a proteasome subunit is the direct cause of a human disease and suggest that decreased proteasome activity can cause inflammation.

Diacylglycerol kinase (DGK) attenuates levels of second messenger diacylglycerol in cells and produces another (putative) messenger, phosphatidic acid. We have previously purified a 110-kDa DGK from rat brain (Kato, M., and Takenawa, T. (1990) J. Biol. Chem. 265, 794 -800). Here we report the cDNA cloning from human brain and retina cDNA libraries. The cDNA encodes a novel DGK isotype, termed DGK, of 941 amino acids with an apparent molecular mass of 110 kDa. DGK contains a C-terminal putative catalytic domain, which is present in all eukaryotic DGKs. In contrast to other DGK isotypes, DGK contains three cysteine-rich domains instead of two. The third cysteine-rich domain is most homologous to the second one in other DGK isotypes. This particular sequence homology extends C-terminally beyond the typical cysteine/histidine core structure and is DGKspecific. DGK furthermore contains various domains for protein-protein interaction, such as a proline-and glycine-rich domain with a putative SH3 domain-binding site and a pleckstrin homology domain with an overlapping Ras-associating domain. DGK is expressed in the brain and, to a lesser extent, in the small intestine, duodenum, and liver. In situ hybridization of DGK mRNA in adult rat brain reveals high expression in the cerebellar cortex and hippocampus. DGK activity in COS cell lysates is optimal toward diacylglycerols containing an unsaturated fatty acid at the sn-2 position.

The protein ASH (for abundant Src homology), composed of one Src homology region (SH) 2 and two SH3 domains, was cloned by screening human and rat cDNA libraries with an oligonucleotide probe directed to a consensus sequence of the SH2 domains. The rat-derived ASH peptide was comprised of 217 amino acids with a molecular mass of 25-28 kDa and was found to be ubiquitous in rat tissues. A human cDNA clone was also found to code for part of the same protein, suggesting that ASH is common to human and rat. The amino acid sequence of ASH was strikingly similar to Sem-5, the product of a nematode cell-signaling gene, and ASH is most probably a mammalian homologue of Sem-5. ASH bound in vitro to phosphotyrosine-containing proteins, including activated epidermal growth factor receptor, the ASH SH2 domain being responsible for the binding. Induced expression of an antisense ASH cDNA led to a reduction in cell growth. Considering these observations and the structural homology to Sem-5, ASH is likely to function as a ubiquitous signal transducer, possibly resembling Sem-5, which communicates between a receptor protein tyrosine kinase and a Ras protein.The Src homology regions (SH) 2 and 3, sequences conserved among noncatalytic regions of nonreceptor tyrosine kinases (1, 2), have been found in a variety of oncogenic, signaling, and cellular substructure-associated proteins (3-8). Both the SH2 and SH3 domains are considered to be involved in intermolecular interactions (for review, see ref. 9). In particular, the SH2 domains bind to subsequences bearing phosphotyrosine (P-Tyr) (10) [or phosphorylated serine/ threonine (11)] in the target molecules such as protein tyrosine kinases, thereby rendering efficient modifications (e.g., tyrosine phosphorylation) to the SH2-containing proteins themselves or their targets (9,12,13 [a-32P]dCTP (Pharmacia system). Of the independent clones, human-derived pSH34 and ratderived pSH030 were selected for further analysis in the present study. An oligo(dT)-primed cDNA library in AgtlO (Amersham system) was constructed with poly(A)+ RNA from the brain of male Fischer 344 rats and was screened by using the cDNA insert of pSH030. A positive clone ARBb was digested with Bgl I/HindIII and subcloned into pBluescript (pRBb), the EcoRI fragment of which was re-subcloned into pBluescript (pRBb3). Both strands of these clones were sequenced at least twice. The nucleic acid sequences were analyzed with the computer program PC/GENE (IntelliGenetics).RNA Blotting Analysis. 3Y1 and TIG-1 cells were inoculated at a split ratio of 1:16 and cultured for 3 days in Dulbecco's modified Eagle's medium/l0o fetal bovine serum. Total RNA was prepared from the cultured cells and various tissues ofadult male Fischer 344 rats by the guanidine method (18). The preparations (10 ,ug each) were separated in a 0.8% formaldehyde agarose gel, blotted to Hybond-N filters, and probed with the cDNA insert of either pSH030 or pSH34 random-labeled with [a-32P]dCTP.Binding of ASH to P-Tyr-Containing Proteins. BamHI-Kpn I ...

The hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) has been shown to be enhanced in cells transformed by some types ofoncogenes and tumor viruses, but it is still unknown whether the breakdown of PIP2 plays a role in oncogene-induced cell proliferation. For examination of this problem, monoclonal antibody specifically directed to PIP2 was nuected into cells. This antibody bound to endogenous PIP2 and so inhibited its intracellular breakdown. lIjection of this antibody into ras-transformed cells cultured in the presence of serum caused reversible and dose-dependent decrease in proliferation and reversion of the cell morphology to that of the normal phenotype. The antibody also inhibited the proliferation of src-and erbB-transformed cells but had no effect on the proliferation of untransformed or myc-transformed cells. These results show that the breakdown ofPIP2 is involved in the signaling pathways for mitogenesis in cells transformed by oncogenes such as ras, src, and erbB.Recent studies on transmembrane signaling pathways (1, 2) have shown that mitogens such as platelet-derived growth factor (PDGF) and bombesin rapidly induce enzymatic breakdown of phosphatidylinositol 4,5-bisphosphate (PIP2), a polyphosphorylated inositolphospholipid, to inositol 1,4,5-trisphosphate (IP3) and 1,2-diacylglycerol. Since these products both act as intracellular second messengers (3-6), IP3 mobilizing Ca2+ from intracellular stores and 1,2-diacylglycerol stimulating protein kinase C activity, stimulation of PIP2 turnover is considered to play an important role in cell proliferation.There is much evidence that some types of oncogenes and tumor viruses enhance inositolphospholipid metabolism during the transformation process (7-9) and modulate the activity of enzymes that catalyze the metabolism of inositolphospholipids (10)(11)(12)(13). Similarly, in ras-transformed cells, enhanced inositolphospholipid metabolism was observed (14, 15) and, by analogy with the GTP-binding protein, the p21 protein encoded by ras was thought to act as a regulatory protein in signal transduction mediated by enhanced inositolphospholipid metabolism (14)(15)(16)(17). In contrast to these results, there are several reports that alteration in inositolphospholipid metabolism is not essential in ras-induced cell transformation (18)(19)(20).Thus, it is uncertain whether inositolphospholipid metabolism is actually important in oncogene-induced cell proliferation. In this study, we examined this problem by injecting a monoclonal antibody against PIP2 into various types of cells. We found that suppression of PIP2 breakdown by the antibody inhibited the proliferations of ras-, src-and erbBtransformed cells but not that of untransformed cells or myc-transformed cells.

The flexural strength of porous Si 3 N 4 ceramics with a variety of microstructures and porosities were evaluated, and the effect of microstructure on the flexural strength was investigated to obtain machinable Si 3 N 4 ceramics having both high strength and high thermal shock resistance. Porous Si 3 N 4 having three types of microstructure, consisting of (1) only spherical grains, (2) combinations of spherical and columnar grains, and (3) only columnar ␤-grains connected randomly in three dimensions, were readied as specimens. Their mean pore diameters and porosities were 0.2 to 0.3 µm and 8% to 59%, respectively. The flexural strength of the porous Si 3 N 4 (3) was much larger than that of the porous Si 3 N 4 having the other microstructures, and the maximum flexural strength was 455 MPa at a porosity of 38.3%. The thermal shock resistance (⌬T), which was determined by a water quench test, of porous Si 3 N 4 with such microstructure and a porosity of 50% was 980 K. All of the porous Si 3 N 4 (3) was easily machined with cemented carbide drills.