Isolation and sequence determination of rat cardiac natriuretic peptide

We have isolated a cardiac natriuretic peptide of 5K daltons from the rat atrium and determined its amino acid sequence. The 5K cardiac natriuretic peptide was elucidated to be a 45-amino acid peptide with the sequence of S-Q-D-S-A-F-R-I-Q-E-R-L-R-N-S-K-M-A-H-S-S-S-C-F-G-Q-K-I-D-R-I-G-A-V-S-R- L-G-C-D - G-L-R-L-F by sequencing the native peptide and its lysyl endopeptidase digests. The sequence of this peptide was identical to the amino acid sequence [51-95] of the rat brain natriuretic peptide (BNP) precursor deduced from the cDNA sequence. The 5K cardiac natriuretic peptide, or BNP[51-95], was identified as the major storage and secretory form derived from the BNP precursor in the rat heart.     

Metabolic activation of carcinogenic ethylbenzene leads to oxidative DNA damage

Ethylbenzene is carcinogenic to rats and mice, while it has no mutagenic activity. We have investigated whether ethylbenzene undergoes metabolic activation, leading to DNA damage. Ethylbenzene was metabolized to 1-phenylethanol, acetophenone, 2-ethylphenol and 4-ethylphenol by rat liver microsomes. Furthermore, 2-ethylphenol and 4-ethylphenol were metabolically transformed to ring-dihydroxylated metabolites such as ethylhydroquinone and 4-ethylcatechol, respectively. Experiment with ³²P-labeled DNA fragment revealed that both ethylhydroquinone and 4-ethylcatechol caused DNA damage in the presence of Cu(II). These dihydroxylated compounds also induced the formation of 8-oxo-7,8-dihydro-2′-deoxyguanosine in calf thymus DNA in the presence of Cu(II). Catalase, methional and Cu(I)-specific chelator, bathocuproine, significantly (P < 0.05) inhibited oxidative DNA damage, whereas free hydroxyl radical scavenger and superoxide dismutase did not. These results suggest that Cu(I) and H₂O₂ produced via oxidation of ethylhydroquinone and 4-ethylcatechol are involved in oxidative DNA damage. Addition of an endogenous reductant NADH dramatically enhanced 4-ethylcatechol-induced oxidative DNA damage, whereas ethylhydroquinone-induced DNA damage was slightly enhanced. Enhancing effect of NADH on oxidative DNA damage by 4-ethylcatechol may be explained by assuming that reactive species are generated from the redox cycle. In conclusion, these active dihydroxylated metabolites would be involved in the mechanism of carcinogenesis by ethylbenzene.     

The structure of bovine F1-ATPase inhibited by ADP and beryllium fluoride

The structure of bovine F1-ATPase inhibited with ADP and beryllium fluoride at 2.0 angstroms resolution contains two ADP.BeF3- complexes mimicking ATP, bound in the catalytic sites of the beta(TP) and beta(DP) subunits. Except for a 1 angstrom shift in the guanidinium of alphaArg373, the conformations of catalytic side chains are very similar in both sites. However, the ordered water molecule that carries out nucleophilic attack on the gamma-phosphate of ATP during hydrolysis is 2.6 angstroms from the beryllium in the beta(DP) subunit and 3.8 angstroms away in the beta(TP) subunit, strongly indicating that the beta(DP) subunit is the catalytically active conformation. In the structure of F1-ATPase with five bound ADP molecules (three in alpha-subunits, one each in the beta(TP) and beta(DP) subunits), which has also been determined, the conformation of alphaArg373 suggests that it senses the presence (or absence) of the gamma-phosphate of ATP. Two catalytic schemes are discussed concerning the various structures of bovine F1-ATPase.     

Prediction of the coding sequences of mouse homologues of FLJ genes: the complete nucleotide sequences of 110 mouse FLJ-homologous cDnas identified by screening of terminal sequences of cDNA clones randomly sampled from size-fractionated libraries.

We have been conducting a mouse cDNA project to predict protein-coding sequences of mouse KIAA-homologous genes since 2001. As an extension of this project, we also started to accumulate mouse cDNA clones homologous to the human FLJ cDNA clones which are another long cDNA resource produced in our institute. We have isolated the cDNA clones from size-fractionated cDNA libraries derived from five different mouse tissues and natural killer T-cells. Although the human FLJ cDNA clones were originally derived from human spleen libraries, one-third of their mouse homologues were obtained from the brain library. We designated these homologues "mFLJ" plus a 5-digit number and herein characterized 110 mFLJ cDNA clones. We assigned an integrity of the CDSs from the comparison of the 110 cDNA clones with the corresponding human FLJ cDNA clones. The average size of the 110 mouse cDNA sequences was 3.8 kb and that of the deduced amino acid sequences from their longest CDS in each cDNA was 663 amino acid residues. Homology and/or motif search against public databases revealed new domains and/or motifs in 26 mFLJ gene products which provide additional speculation regarding the function of FLJ genes.     

Requirement for Tec kinases in chemokine-induced migration and activation of Cdc42 and Rac

Cell polarization and migration in response to chemokines is essential for proper development of the immune system and activation of immune responses. Recent studies of chemokine signaling have revealed a critical role for PI3-Kinase, which is required for polarized membrane association of pleckstrin homology (PH) domain-containing proteins and activation of Rho family GTPases that are essential for cell polarization and actin reorganization. Additional data argue that tyrosine kinases are also important for chemokine-induced Rac activation. However, how and which kinases participate in these pathways remain unclear. We demonstrate here that the Tec kinases Itk and Rlk play an important role in chemokine signaling in T lymphocytes. Chemokine stimulation induced transient membrane association of Itk and phosphorylation of both Itk and Rlk, and purified T cells from Rlk(-/-)Itk(-/-) mice exhibited defective migration to multiple chemokines in vitro and decreased homing to lymph nodes upon transfer to wt mice. Expression of a dominant-negative Itk impaired SDF-1alpha-induced migration, cell polarization, and activation of Rac and Cdc42. Thus, Tec kinases are critical components of signaling pathways required for actin polarization downstream from both antigen and chemokine receptors in T cells.     

Spontaneous Release of γ-Aminobutyric Acid Formed from Putrescine and Its Enhanced Ca2+-Dependent Release by High K+ Stimulation in the Brains of Freely Moving Rats

The spontaneous release of [3H] gamma-aminobutyric acid ([3H]GABA) in various areas of rat brain injected with [3H]putrescine was examined using a push-pull perfusion technique. The release in a 25-min perfusate was highest in the caudate-putamen. The effect of high K+ stimulation on the release of [3H]GABA formed from [3H]putrescine was examined in the caudate-putamen. The release was enhanced by high K+ solution in a Ca2+-dependent manner.     

Integrated Copy Number and Expression Analysis Identifies Profiles of Whole-Arm Chromosomal Alterations and Subgroups with Favorable Outcome in Ovarian Clear Cell Carcinomas

Ovarian clear cell carcinoma (CCC) is generally associated with chemoresistance and poor clinical outcome, even with early diagnosis; whereas high-grade serous carcinomas (SCs) and endometrioid carcinomas (ECs) are commonly chemosensitive at advanced stages. Although an integrated genomic analysis of SC has been performed, conclusive views on copy number and expression profiles for CCC are still limited. In this study, we performed single nucleotide polymorphism analysis with 57 epithelial ovarian cancers (31 CCCs, 14 SCs, and 12 ECs) and microarray expression analysis with 55 cancers (25 CCCs, 16 SCs, and 14 ECs). We then evaluated PIK3CA mutations and ARID1A expression in CCCs. SNP array analysis classified 13% of CCCs into a cluster with high frequency and focal range of copy number alterations (CNAs), significantly lower than for SCs (93%, P < 0.01) and ECs (50%, P = 0.017). The ratio of whole-arm to all CNAs was higher in CCCs (46.9%) than SCs (21.7%; P < 0.0001). SCs with loss of heterozygosity (LOH) of BRCA1 (85%) also had LOH of NF1 and TP53, and LOH of BRCA2 (62%) coexisted with LOH of RB1 and TP53. Microarray analysis classified CCCs into three clusters. One cluster (CCC-2, n = 10) showed more favorable prognosis than the CCC-1 and CCC-3 clusters (P = 0.041). Coexistent alterations of PIK3CA and ARID1A were more common in CCC-1 and CCC-3 (7/11, 64%) than in CCC-2 (0/10, 0%; P < 0.01). Being in cluster CCC-2 was an independent favorable prognostic factor in CCC. In conclusion, CCC was characterized by a high ratio of whole-arm CNAs; whereas CNAs in SC were mainly focal, but preferentially caused LOH of well-known tumor suppressor genes. As such, expression profiles might be useful for sub-classification of CCC, and might provide useful information on prognosis.     

Structure and Regulation of the Movement of Human Myosin VIIA

Human myosin VIIA (HM7A) is responsible for human Usher syndrome type 1B, which causes hearing and visual loss in humans. Here we studied the regulation of HM7A. The actin-activated ATPase activity of full-length HM7A (HM7AFull) was lower than that of tail-truncated HM7A (HM7AΔTail). Deletion of the C-terminal 40 amino acids and mutation of the basic residues in this region (R2176A or K2179A) abolished the inhibition. Electron microscopy revealed that HM7AFull is a monomer in which the tail domain bends back toward the head-neck domain to form a compact structure. This compact structure is extended at high ionic strength or in the presence of Ca²⁺. Although myosin VIIA has five isoleucine-glutamine (IQ) motifs, the neck length seems to be shorter than the expected length of five bound calmodulins. Supporting this observation, the IQ domain bound only three calmodulins in Ca²⁺, and the first IQ motif failed to bind calmodulin in EGTA. These results suggest that the unique IQ domain of HM7A is important for the tail-neck interaction and, therefore, regulation. Cellular studies revealed that dimer formation of HM7A is critical for its translocation to filopodial tips and that the tail domain (HM7ATail) markedly reduced the filopodial tip localization of the HM7AΔTail dimer, suggesting that the tail-inhibition mechanism is operating in vivo. The translocation of the HM7AFull dimer was significantly less than that of the HM7AΔTail dimer, and R2176A/R2179A mutation rescued the filopodial tip translocation. These results suggest that HM7A can transport its cargo molecules, such as USH1 proteins, upon release of the tail-dependent inhibition.