A novel potent vasoconstrictor peptide produced by vascular endothelial cells

An endothelium-derived 21-residue vasoconstrictor peptide, endothelin, has been isolated, and shown to be one of the most potent vasoconstrictors known. Cloning and sequencing of preproendothelin complementary DNA shows that mature endothelin is generated through an unusual proteolytic processing, and regional homologies to a group of neurotoxins suggest that endothelin is an endogenous modulator of voltage-dependent ion channels. Expression of the endothelin gene is regulated by several vasoactive agents, indicating the existence of a novel cardiovascular control system.

The relationship between in vitro cellular aging and in vivo human age

Differences between early and late passage cell cultures on the organelle and macromolecular levels have been attributed to cellular "aging". However, concern has been expressed over whether changes in diploid cell populations after serial passage in vitro accurately reflect human cellular aging in vivo. Studies were therefore undertaken to determine if significant differences would be observed in the in vitro lifespans of skin fibroblast cultures from old and young normal, non-hospitalized volunteers and to examine if parameters that change with in vitro "aging" are altered as a function of age in vivo. Statistically signigificant (P less than 0.05) decreases were found in the rate of fibroblast migration, onset of cell culture senescence, in vitro lifespan, cell population replication rate, and cell number at confluency of fibroblast cultures derived from the old donor group when compared to parallel cultures from young donors. No significant differences were observed in modal cell volumes and cellular macromolecular contents. The differences observed in cell cultures from old and young donors were quantitatively and qualitatively distinct from those cellular alterations observed in early and late passage WI-38 cells (in vitro "aging"). Therefore, although early and late passage cultures of human diploid cells may provide an important cell system for examining loss of replicative potential, fibroblast cultures derived from old and young human donors may be a more appropriate model system for studying human cellular aging.

Cloning and sequence analysis of cDNA encoding the precursor of a human endothelium-derived vasoconstrictor peptide, endothelin: identity of human and porcine endothelin

A cDNA encoding a human endothelium-derived vasoconstrictor peptide, endothelin, was isolated from a human placenta cDNA library. The nucleotide sequence of this cDNA clone showed that the primary structure of the human preproendothelin has 212 amino acid residues and is highly homologous to porcine preproendothelin, and that human endothelin is identical with porcine endothelin.

Fluorescence behavior of tryptophan residues of bovine and human serum albumins in ionic surfactant solutions: a comparative study of the two and one tryptophan(s) of bovine and human albumins

The fluorescence behavior of two tryptophans (Trp-134, Trp-213) in bovine serum albumin (BSA) and a single tryptophan (Trp-214) in human serum albumin (HSA) was examined. The maximum emission wavelength (lambda max) was 340.0 nm for both proteins. In a solution of sodium dodecyl sulfate (SDS), the lambda max of BSA abruptly shifted to 332 nm at 1 mM SDS and then reversed to 334 nm at 3 mM SDS. The lambda max of HSA gradually shifted to 330 nm below 3 mM SDS, although it returned to 338 nm at 10 mM SDS. In contrast to this, in a solution of dodecltrimethylammonium bromide, the lambda max positions of BSA and HSA gradually shifted to 334.0 and 331.5 nm, respectively. Differences in the fluorescence behavior of the proteins are attributed to the fact that Trp-134 exists only in BSA, with the assumption that Trp-213 of BSA behaves the same as Trp-214 of HSA. The Trp-134 behavior appears to relate to the disruption of the helical structure in the SDS solution.

Crystal structures of the binary and ternary complexes of 7 alpha-hydroxysteroid dehydrogenase from Escherichia coli

7 alpha-Hydroxysteroid dehydrogenase (7 alpha-HSDH;1 EC 1.1.1.159) is an NAD+-dependent oxidoreductase belonging to the short-chain dehydrogenase/reductase (SDR) 1 family. It catalyzes the dehydrogenation of a hydroxyl group at position 7 of the steroid skeleton of bile acids. The crystal structure of the binary (complexed with NAD+) complex of 7 alpha-HSDH has been solved at 2.3 A resolution by the multiple isomorphous replacement method. The structure of the ternary complex [the enzyme complexed with NADH, 7-oxoglycochenodeoxycholic acid (as a reaction product), and possibly partially glycochenodeoxycholic acid (as a substrate)] has been determined by a difference Fourier method at 1.8 A resolution. The enzyme 7 alpha-HSDH is an alpha/beta doubly wound protein having a Rossmann-fold domain for NAD (H) binding. Upon substrate binding, large conformation changes occur at the substrate binding loop (between the beta F strand and alpha G helix) and the C-terminal segment (residues 250-255). The variable amino acid sequences of the substrate-binding loop appear to be responsible for the wide variety of substrate specificities observed among the enzymes of the SDR family. The crystal structure of the ternary complex of 7 alpha-HSDH, which is the only structure available as the ternary complex among the enzymes of the SDR family, indicates that the highly conserved Tyr159 and Ser146 residues most probably directly interact with the hydroxyl group of the substrates although this observation cannot be definite due to an insufficiently characterized nature of the ternary complex. The strictly conserved Lys163 is hydrogen-bonded to both the 2'- and 3'-hydroxyl groups of the nicotinamide ribose of NAD(H). We propose a new catalytic mechanism possibly common to all the enzymes belonging to the SDR family in which a tyrosine residue (Tyr159) acts as a catalytic base and a serine residue (Ser146) plays a subsidiary role of stabilizing substrate binding.

Crystal structure of the ternary complex of mouse lung carbonyl reductase at 1.8 A resolution: the structural origin of coenzyme specificity in the short-chain dehydrogenase/reductase family

BACKGROUND

Mouse lung carbonyl reductase (MLCR) is a member of the short-chain dehydrogenase/reductase (SDR) family. Although it uses both NADPH and NADH as coenzymes, the structural basis of its strong preference for NADPH is unknown.

RESULTS

The crystal structure of the ternary complex of MLCR (with NADPH and 2-propanol) has been determined at 1.8 A resolution. This is the first three-dimensional structure of a carbonyl reductase, and MLCR is the first member of the SDR family to be solved in complex with NADPH (rather than NADH). Comparison of the MLCR ternary complex with three structures reported previously for enzymes of the SDR family (all crystallized as complexes with NADH) reveals a pair of basic residues (Lys17 and Arg39) making strong electrostatic interactions with the 2'-phosphate group of NADPH. This pair of residues is well conserved among the NADPH-preferring enzymes of the SDR family, but not among the NADH-preferring enzymes. In the latter, an aspartate side chain occupies the position of the two basic side chains. The aspartate residue, which would come into unacceptably close contact with the 2'-phosphate group of the adenosine moiety of NADPH, is replaced by a threonine or alanine in the primary sequences of NADPH-preferring enzymes of the SDR family.

CONCLUSIONS

The cofactor preferences exhibited by the enzymes of the SDR family are mainly determined by the electrostatic environment surrounding the 2'-hydroxyl (or phosphate) group of the adenosine ribose moiety of NADH (or NADPH). Thus, positively charged and negatively charged environments correlate with preference for NADPH and NADH respectively.

Inactivation of tumor suppressor p53 by mot-2, a hsp70 family member

The mortalin genes, mot-1 and mot-2, are hsp70 family members that were originally cloned from normal and immortal murine cells, respectively. Their proteins differ by only two amino acid residues but exhibit different subcellular localizations, arise from two distinct genes, and have contrasting biological activities. We report here that the two proteins also differ in their interactions with the tumor suppressor protein p53. The pancytosolic mot-1 protein in normal cells did not show colocalization with p53; in contrast, nonpancytosolic mot-2 and p53 overlapped significantly in immortal cells. Transfection of mot-2 but not mot-1 resulted in the repression of p53-mediated transactivation in p53-responsive reporter assays. Inactivation of p53 by mot-2 was supported by the down-regulation of p53-responsive genes p21(WAF-1) and mdm-2 in mot-2-transfected cells only. Furthermore, NIH 3T3 cells transfected with expression plasmid encoding green fluorescent protein-tagged mot-2 but not mot-1 showed an abrogation of nuclear translocation of wild-type p53. These results demonstrate a novel mechanism of p53 inactivation by mot-2 protein.

Pro- and Anti-inflammatory Cytokine Gene Expression in Rat Sciatic Nerve Chronic Constriction Injury Model of Neuropathic Pain

Cytokines may be pathophysiologically involved in hyperalgesia. Uncertainty exists about the types of cytokines and their site of action. To study the role of key pro- and anti-inflammatory cytokines in a chronic constriction model of neuropathic pain, mRNA expression of TNF, IL-1beta, IL-6, and IL-10 was quantified using competitive RT-PCR. Each cytokine mRNA in rat sciatic nerve was examined at days 3, 7, 14, and 45 after chronic constriction injury (CCI). We also undertook behavioral testing of these rats. Thermal warming and touch thresholds were significantly reduced at days 3, 7, and 14 in the CCI group, compared with the sham-operated group. Cytokine gene expression in sciatic nerve was significantly increased at day 7 for IL-1beta and IL-6 and at day 14 for TNF. Expression of IL-10 underwent a gradual and progressive increase, reaching statistical significance at day 45.

cDNA cloning, sequence analysis and tissue distribution of rat preproendothelin-1 mRNA

We report the cloning of a full-length cDNA encoding rat preproendothelin-1 (preproET-1). The predicted rat preproET-1 consists of 202 amino acid residues and highly similar to human, porcine and bovine preproET-1, respectively. The deduced 21-residue sequence of mature rat ET-1 is identical to human, porcine, canine and bovine ET-1. As in other mammalian species, the mature ET-1 is predicted to be produced from a 39-residue big ET-1 in the rat. Northern blot analysis showed that a single 2.3-kb preproET-1 mRNA is expressed not only in vascular endothelial cells but also in other rat tissues, including the lung, brain, uterus, stomach, heart, adrenal gland and kidney. These findings suggest that ET-1 may play roles as a local mediator in multiple organs both within and outside the cardiovascular system in the rat.

Three-dimensional structures of free form and two substrate complexes of an extradiol ring-cleavage type dioxygenase, the BphC enzyme from Pseudomonas sp. strain KKS102

The crystal structure of an enzyme having polychlorinated-biphenyl degrading activity, the BphC enzyme from Pseudomonas sp. strain KKS102, has been solved as a free form at 1.8 A resolution. This is the first three-dimensional structure among the extradiol-type dioxygenases. Based on 34,387 reflections (10.0 to 1.8 A, completeness 87.8%), a current R-factor of 20.4% (with a free R-factor of 24.3%) was obtained with a model obeying standard geometry within 0.011 A in bond lengths and 1.91 degrees in bond angles. The BphC enzyme is a homo-octamer and each subunit is composed of two domains: Domain 1 (N-terminal part) and Domain 2 (C-terminal part). Each domain contains two repetitions of a novel folding motif (the "beta alpha beta beta beta" motif) each consisting of ca 55 amino acid residues. A single Fe ion in the active site coordinates the side-chains of three amino acid residues (His145, His209 and Glu260) and two solvent molecules. The coordination geometry is that of a square pyramid. In addition to the free form of the BphC enzyme, we have solved two three-dimensional structures of the BphC enzyme complexed with its substrates, 2,3-dihydroxybiphenyl (2,3-DHBP) or 3-methylcatechol (3-MCT). These substrates were found intact in the active site probably because of the oxidation of the Fe ion into ferric form (as judged by EPR spectra) in the present crystals. In both of the two substrate complexes, the two hydroxyl groups of the substrate, together with the three enzymatic side-chain ligands, were found to form a penta-coordinated system around the Fe ion roughly arranged in a trigonal bipyramidal configuration. The active site structures appear to be essentially consistent with the reaction mechanism proposed so far.

Extended longevity of Caenorhabditis elegans by knocking in extra copies of hsp70F, a homolog of mot-2 (mortalin)/mthsp70/Grp75

The Caenorhabditis elegans homolog of mortalin/mthsp70/Grp75 (called mot-2 hereafter) was isolated by screening of a nematode cDNA library with mouse mot-2 cDNA. The isolated clone matched to hsp70F of C. elegans. Analysis with two of the antibodies raised against hsp70F revealed that unlike mammalian mot-2, it is heat inducible. Transient induction of hsp70F by heat shock led to a slight (<13%) extension in the C. elegans life span. The transgenic worms that constitutively over-expressed hsp70F predominantly in muscle showed life span extension (approximately 43% for mean and approximately 45% for maximum life span) as compared to the wild-type and green fluorescent protein-transgenic worms. Life span extension of human cells was obtained by over-expression of mot-2 [Kaul et al. (2000) FEBS Lett. 474, 159-164]. Our results show, for the first time, that this member of the hsp70 family governs the longevity of worms and thus there are common pathways that determine mammalian and worm longevity.

Fluorescent differential display: arbitrarily primed RT-PCR fingerprinting on an automated DNA sequencer

We established robust, reliable protocols for 'Differential Display (DD),' an RNA fingerprinting method originally developed by Liang and Pardee [(1992) Science 257, 967-971] using RT-PCR with arbitrary primers. Our protocols are optimized so that reliable DD analysis can be performed on a fluorescent DNA sequencer to ensure high throughput as well as improved operational safety, compared with the original one using radioactive compounds. Such 'Fluorescent Differential Display (FDD)' techniques will accelerate the identification of differentially expressed as well as polymorphic transcripts to address various biological questions.

Crystal structure of an aromatic ring opening dioxygenase LigAB, a protocatechuate 4,5-dioxygenase, under aerobic conditions

BACKGROUND

Sphingomonas paucimobilis SYK-6 utilizes an extradiol-type catecholic dioxygenase, the LigAB enzyme (a protocatechuate 4,5-dioxygenase), to oxidize protocatechuate (or 3,4-dihydroxybenzoic acid, PCA). The enzyme belongs to the family of class III extradiol-type catecholic dioxygenases catalyzing the ring-opening reaction of protocatechuate and related compounds. The primary structure of LigAB suggests that the enzyme has no evolutionary relationship with the family of class II extradiol-type catecholic dioxygenases. Both the class II and class III enzymes utilize a non-heme ferrous center for adding dioxygen to the substrate. By elucidating the structure of LigAB, we aimed to provide a structural basis for discussing the function of class III enzymes.

RESULTS

The crystal structure of substrate-free LigAB was solved at 2.2 A resolution. The molecule is an alpha2beta2 tetramer. The active site contains a non-heme iron coordinated by His12, His61, Glu242, and a water molecule located in a deep cleft of the beta subunit, which is covered by the alpha subunit. Because of the apparent oxidation of the Fe ion into the nonphysiological Fe(III) state, we could also solve the structure of LigAB complexed with a substrate, PCA. The iron coordination sphere in this complex is a distorted tetragonal bipyramid with one ligand missing, which is presumed to be the O2-binding site.

CONCLUSIONS

The structure of LigAB is completely different from those of the class II extradiol-type dioxygenases exemplified by the BphC enzyme, a 2,3-dihydroxybiphenyl 1,2-dioxygenase from a Pseudomonas species. Thus, as already implicated by the primary structures, no evolutionary relationship exists between the class II and III enzymes. However, the two classes of enzymes share many geometrical characteristics with respect to the nature of the iron coordination sphere and the position of a putative catalytic base, strongly suggesting a common catalytic mechanism.

Presynaptic effects of botulinum toxin type A on the neuronally evoked response of albino and pigmented rabbit iris sphincter and dilator muscles

PURPOSE

To investigate the effects of botulinum toxin type A (botulinum A toxin) on the autonomic and other nonadrenergic, noncholinergic nerve terminals.

METHODS

The effects of botulinum A toxin on twitch contractions evoked by electrical field stimulation (EFS) were studied in isolated albino and pigmented rabbit iris sphincter and dilator muscles using the isometric tension recording method.

RESULTS

Botulinum A toxin inhibited the fast cholinergic and slow substance P-ergic component of the contraction evoked by EFS in the rabbit iris sphincter muscle without affecting the response to carbachol and substance P. These inhibitory effects were more marked in the albino rabbit than in the pigmented rabbit. Botulinum A toxin (150 nmol/L) did not affect the twitch contraction evoked by EFS in the rabbit iris dilator muscle.

CONCLUSIONS

These data indicated that botulinum A toxin may inhibit not only the acetylcholine release in the cholinergic nerve terminals, but also substance P release from the trigeminal nerve terminals of the rabbit iris sphincter muscle. However, the neurotoxin has little effect on the adrenergic nerve terminals of the rabbit iris dilator muscle. Furthermore, the botulinum A toxin binding to the pigment melanin appears to influence the response quantitatively in the two types of irides.

Hsp70 family member, mot-2/mthsp70/GRP75, binds to the cytoplasmic sequestration domain of the p53 protein

Hsp70 family member mot-2/mthsp70/GRP75/PBP74 was shown to bind to the tumor suppressor protein p53. In this study, by in vivo coimmunoprecipitation of mot-2 with p53 and its deletion mutants, the mot-2 binding site of p53 was mapped to its C-terminal amino acid residues 312-352, a region of p53 that includes its cytoplasmic sequestration domain. These data demonstrate that cytoplasmic sequestration and inactivation of p53 by mot-2 occurs by its binding to the cytoplasmic sequestration domain. Therefore, perturbation of mot-p53 interactions can be employed to abrogate cytoplasmic retention of wild-type p53 in tumors.

Relationship between cell replication and volume in senescent human diploid fibroblasts

Since alterations in cell replication rate and cell volume distribution are two of the earliest changes seen in the culture of human diploid cells, it was decided to examine the relationship between these parameters. After standardization of the conditions for cell volume measurements (enzyme treatment, temperature and stage of cell growth), a close correlation was observed between cell population doubling time and cell volume in WI-38 cells at various levels of in vitro passage. Cell populations which replicate more slowly (trisomic-21 fibroblasts, fetal skin fibroblasts) also demonstrated a shift to larger cell volumes when compared with control rapidly replicating cell populations at the same level of in vitro passage. Similar shifts to larger cell volumes were produced by reducing serum concentration, decreasing incubation temperature and inhibiting DNA synthesis. Separation of senescent WI-38 cells on the basis of cell volume revealed that the cell fractions with the largest modal cell volume contained the highest percentage of slow or nonreplicating cells. Therefore, an inverse relationship appears to exist between growth rate and cell volume in cultured human diploid fibroblasts.

Endothelin-1 is produced and secreted by neonatal rat cardiac myocytes in vitro

Production of endothelin-1 in the cultured neonatal rat cardiac myocytes was investigated. Studies on the cultured cardiac myocytes with reverse transcription-polymerase chain reaction followed by Southern hybridization indicated that mRNA of ET-1(preproET-1 mRNA) was expressed by cardiac myocytes. ET-1 polypeptide was also detected in the cultured cardiac myocytes. Moreover, ET-1 was secreted into the culture medium by them. These results suggest that the cardiac myocytes, which have been regarded as target cells of ET-1, are able to synthesize and secrete ET-1. Furthermore, there may be a possible autocrine mechanism of ET-1 in the myocytes of a heart.

5-Bromodeoxyuridine induces senescence-like phenomena in mammalian cells regardless of cell type or species

5-Bromodeoxyuridine was found to induce flat and enlarged cell shape, characteristics of senescent cells, and senescence-associated beta-galactosidase in mammalian cells regardless of cell type or species. In immortal human cells, fibronectin, collagenase I, and p21(wafl/sdi-1) mRNAs were immediately and very strongly induced, and the mortality marker mortalin changed to the mortal type from the immortal type. Human cell lines lacking functional p21(wafl/sdi-1), p16(ink4a), or p53 behaved similarly. The protein levels of p16(ink4a) and p53 did not change uniformly, while the level of p21(wafl/sdi-1) was increased by varying degrees in positive cell lines. Telomerase activity was suppressed in positive cell lines, but accelerated telomere shortening was not observed in tumor cell lines. These results suggest that 5-bromodeoxyuridine activates a common senescence pathway present in both mortal and immortal mammalian cells.

Differential regulation of human RecQ family helicases in cell transformation and cell cycle

Three human RecQ DNA helicases, WRN, BLM and RTS, are involved in the genetic disorders associated with genomic instability and a high incidence of cancer. RecQL1 and RecQL5 also belong to the human RecQ helicase family, but their correlation with genetic disorders, if any, is unknown. We report here that in human B cells transformed by Epstein-Barr virus (EBV), human fibroblasts and umbilical endothelial cells transformed by simian virus 40, the expression of WRN, BLM, RTS and RecQL1 was sharply up-regulated. In B cells this expression was stimulated within 5-40 h by the tumor promoting agent phorbol myristic acetate (PMA). Interestingly, RecQL5beta, an alternative splicing product of RecQL5 with a nuclear localization signal, is expressed in resting B cells without significant modulation of its synthesis by EBV or PMA, suggesting it has a role in resting cells. We also roughly determined the number of copies per cell for the five RecQ helicase in B cells. In addition, levels of the different RecQ helicases are modulated in different ways during the cell cycle of actively proliferating fibroblasts and umbilical endothelial cells. Our results support the view that the levels of WRN, BLM, RTS and RecQL1 are differentially up-regulated to guarantee genomic stability in cells that are transformed or actively proliferating.

Three-dimensional crystal structure of recombinant murine interferon-beta

The crystal structure of recombinant murine interferon-beta (IFN-beta) has been solved by the multiple isomorphous replacement method and refined to an R-factor of 20.5% against 2.6 A X-ray diffraction data. The structure shows a variant of the alpha-helix bundle with a new chain-folding topology, which seems to represent a basic structural framework of all the IFN-alpha and IFN-beta molecules belonging to the type I family. Functionally important segments of the polypeptide chain, as implied through numerous gene manipulation studies carried out so far, are spatially clustered indicating the binding site(s) to the receptor(s). Comparison of the present structure with those of other alpha-helical cytokine proteins, including porcine growth hormone, interleukin 2 and interferon gamma, indicated either a topological similarity in chain folding or a similar spatial arrangement of the alpha-helices.