Unidentified Protein (unidentified + protein)

Distribution by Scientific Domains

Selected Abstracts

NUB1-mediated targeting of the ubiquitin precursor UbC1 for its C-terminal hydrolysis

FEBS JOURNAL, Issue 5 2004
Tomoaki Tanaka
NEDD8 is a ubiquitin-like protein that controls vital biological events through its conjugation to target proteins. Previously, we identified a negative regulator of the NEDD8 conjugation system, NEDD8 ultimate buster-1 (NUB1), that recruits NEDD8 and its conjugates to the proteasome for degradation. Recently, we performed yeast two-hybrid screening with NUB1 as bait and isolated a ubiquitin precursor UbC1 that is composed of nine tandem repeats of a ubiquitin unit through ,-peptide bonds. Interestingly, NUB1 interacted with UbC1 through its UBA domain. Further study revealed that the UBA domain interacted with ,-peptide bond-linked polyubiquitin, but not with isopeptide bond-linked polyubiquitin, indicating that the UBA domain of NUB1 is a specific acceptor for the linear ubiquitin precursor. A functional study revealed that an unidentified protein that was immunoprecipitated with NUB1 served as a ubiquitin C-terminal hydrolase for UbC1. Thus, NUB1 seems to form a protein complex with the unidentified ubiquitin C-terminal hydrolase and recruit UbC1 to this complex. This might allow the ubiquitin C-terminal hydrolase to hydrolyze UbC1, in order to generate ubiquitin monomers. Northern blot analysis showed that the mRNAs of both NUB1 and UbC1 were enriched in the testis. Furthermore, in situ hybridization showed that both mRNAs were strongly expressed in seminiferous tubules of the testis. These results may imply that the UbC1 hydrolysis mediated by NUB1 is involved in cellular functions in the seminiferous tubules such as spermatogenesis. [source]

Expression of glutathione transferase isoenzymes in the human H295R adrenal cell line and the effect of forskolin

Tuula Stark
Abstract In previous studies in our laboratory (L. Mankowitz, L. Staffas, M. Bakke, and J. Lund, Biochem J, 1995, 305, 111,118; L. Staffas, L. Mankowitz, M. Söderström, A. Blanck, I. Porsch-Hällström, C. Sundberg, B. Mannervik, B. Olin, J. Rydström, and J.W. DePierre, Biochem J, 1992, 286, 65,72) isoenzymes of GST, primarily of the , class, have been shown to be downregulated by adrenocorticotropic hormone (ACTH) in rat and mouse adrenal cells. In the present investigation the human adrenal H295R cell line (W.E. Rainey, I.M. Bird, and J.I. Mason, Mol Cell Endocrinol, 1994, 100, 45,50) was examined in a similar manner. Analysis by reverse-phase HPLC revealed that these cells express four isoenzymes of GST, i.e., A1, A2, P1, and M4, as well as another unidentified protein that was retained by our affinity column (elution time of 32 min) and, thus, presumably binds glutathione. Among these forms, A1 was present at the highest level. Upon addition of forskolin (an activator of adenylate cyclase which has been shown previously to mimic the effect of ACTH on adrenal cells) to the culture medium, the level of A1 decreased approximately 70% by forskolin, whereas the levels of the other isoenzymes were slightly increased, and that of the unknown form doubled. Thus, the influence of ACTH on expression of GST isoenzymes in this human adrenal cell line differs from that in rat and mouse adrenal cells. © 2002 Wiley Periodicals, Inc. J Biochem Mol Toxicol 16:169,173, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.10034 [source]

Novel UBA Domain Mutations of SQSTM1 in Paget's Disease of Bone: Genotype Phenotype Correlation, Functional Analysis, and Structural Consequences

Lynne J Hocking
Abstract Three novel missense mutations of SQSTM1 were identified in familial PDB, all affecting the UBA domain. Functional and structural analysis showed that disease severity was related to the type of mutation but was unrelated to the polyubiquitin-binding properties of the mutant UBA domain peptides. Introduction: Mutations affecting the ubiquitin-associated (UBA) domain of Sequestosome 1 (SQSTM1) gene have recently been identified as a common cause of familial Paget's disease of bone (PDB), but the mechanisms responsible are unclear. We identified three novel SQSTM1 mutations in PDB, conducted functional and structural analyses of all PDB-causing mutations, and studied the relationship between genotype and phenotype. Materials and Methods: Mutation screening of the SQSTM1 gene was conducted in 70 kindreds with familial PDB. We characterized the effect of the mutations on structure of the UBA domain by protein NMR, studied the effects of the mutant UBA domains on ubiquitin binding, and looked at genotype-phenotype correlations. Results and Conclusions: Three novel missense mutations affecting the SQSTM1 UBA domain were identified, including a missense mutation at codon 411 (G411S), a missense mutation at codon 404 (M404V), and a missense mutation at codon 425 (G425R). We also identified a deletion leading to a premature stop codon at 394 (L394X). None of the mutations were found in controls. Structural analysis showed that M404V and G425R involved residues on the hydrophobic surface patch implicated in ubiquitin binding, and consistent with this, the G425R and M404V mutants abolished the ability of mutant UBA domains to bind polyubiquitin chains. In contrast, the G411S and P392L mutants bound polyubiquitin chains normally. Genotype-phenotype analysis showed that patients with truncating mutations had more extensive PDB than those with missense mutations (bones involved = 6.05 ± 2.71 versus 3.45 ± 2.46; p < 0.0001). This work confirms the importance of UBA domain mutations of SQSTM1 as a cause of PDB but shows that there is no correlation between the ubiquitin-binding properties of the different mutant UBA domains and disease occurrence or extent. This indicates that the mechanism of action most probably involves an interaction between SQSTM1 and a hitherto unidentified protein that modulates bone turnover. [source]

Motor neuron disease group accompanied by inclusions of unidentified protein signaled by ubiquitin

Kenji Ikeda
Peculiar tau-negative, ubiquitin-positive inclusions appear in dementia with ALS (ALS-D), the majority of lobar atrophy (Pick's disease) without Pick body and a small portion of ALS. Another common neuropathological lesion in these diseases is the motor neuron involvement with the degenerative processes. The lower motor neuron is predominantly involved in ALS and ALS-D while the upper motor neuron is predominantly involved, but in varying degrees in a considerable number of patients with lobar atrophy that lack Pick bodies. There are, however, some points that have yet to be elucidated. The boundary between these diseases is not always clear and a significant number of cases are considered to be the transitional form. Lobar atrophy without Pick body seems to be a heterogeneous disease group. The nature of ubiquitin inclusions also needs to be clarified. Nevertheless, we postulate that these diseases are grouped with the concept of motor neuron disease-inclusion dementia. [source]

Effect of celecoxib on cyclooxygenase-2 expression and possible variants in a patient with Barrett's esophagus

G. A. Jacobson
SUMMARY., Cyclooxygenase-2 (COX-2) expression is increased in metaplastic and dysplastic Barrett's esophageal epithelium and it is thought that selective COX-2 inhibitors could offer hope as chemoprevention therapy. The aim of the study was to investigate the in vivo effect of celecoxib on COX-2 expression in patients with Barrett's esophagus and no recent history of non-steroidal anti-inflammatory drug use. Endoscopic mucosal biopsy specimens were collected at baseline and after 28 days of therapy in a patient treated with celecoxib 200 mg twice daily. Samples were analyzed for COX-2 expression by immunoblot analysis with chemiluminescence detection. COX-2 expression was found to decline 20% and 44% at two different biopsy sites compared to the baseline sample. Longer exposures revealed a number of previously unidentified proteins above and below the 67 kDa COX-2 protein including 38 kDa and 45 kDa proteins which were present only at study completion consistent with up-regulation after celecoxib therapy. Further investigations of the 38 kDa and 45 kDa proteins were undertaken using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) with immunoblot and MALDI-TOF (matrix assisted laser desorption ionization , time of flight) analysis but no matches were found and results were inconclusive. Unmatched masses from MALDI-TOF peptide mass fingerprinting were compared with human COX-2 (67 kDa) and COX-2b (39 kDa) using unspecific cleavage. Peptide sequence homology with COX-2 and COX-2b was found for a length of 19 amino acids. Based on immunodetection, molecular weight and equivical MALDI-TOF results, one of these up-regulated proteins may be COX-2b. [source]

Xenobiotic response element binding enriched in both nuclear and microsomal fractions of rat cerebellum

Nobuyuki Kuramoto
Abstract Xenobiotic response element (XRE) is a core nucleotide sequence at the upstream of inducible target genes for the transcription factor aryl hydrocarbon receptor (AhR) that is responsible for signal transduction of exogenous environmental pollutants in eukaryotic cells. Immunoblotting analysis revealed the constitutive expression of AhR-related proteins in rat liver and brain, while specific binding of a radiolabelled probe containing XRE was detected in nuclear preparations of both liver and brain on gel retardation electrophoresis. Among discrete rat brain structures examined, cerebellum exhibited the highest XRE binding with less potent binding in hypothalamus, midbrain, medulla-oblongata, hippocampus, cerebral cortex and striatum. In contrast to liver and hippocampus, cerebellum also contained unusually higher XRE binding in microsomal fractions than that in either nuclear or mitochondrial fractions. Limited proteolysis by V8 protease did not markedly affect XRE binding in cerebellar nuclear extracts, with concomitant diminution of that in hepatic and hippocampal nuclear extracts. In primary cultured cerebellar neurons, indigo was effective in significantly increasing XRE binding only when determined immediately after sustained exposure for 120 min in the presence of high potassium chloride. These results suggest the abundance of as-yet unidentified proteins with high affinity for XRE and responsiveness to indigo in both nuclear and microsomal fractions of rat cerebellum. [source]