Constitutive Synthesis Research Articles

Melanin Synthesis Is Associated with Changes in Hyphopodial Turgor, Permeability, and Wall Rigidity inGaeumannomyces graminisvar.graminis

Mycelia ofGaeumannomyces graminisvar.graminisform large cells called hyphopodia with deeply lobed, melanized walls. Like appressoria produced by other pathogens, hyphopodia develop on hydrophobic surfaces, but it is not clear that hyphopodia function as platforms for host penetration. In appressoria, melanin synthesis is linked to the generation of enormous turgor pressures that provide the necessary force for plant penetration. In the present study, hyphopodial turgor was measured in a wild-type strain ofG. graminisvar.graminis,a mutant exhibiting constitutive synthesis of melanin (referred to as the dark mutant), and a melanin-deficient strain (thr). These experiments demonstrate that hyphopodia of the wild-type strain generate higher pressures than the dark mutant and that nonmelanizedthrhyphopodia generate minuscule internal pressures. Melanization of the wall is also associated with an increase in its rigidity. These data correlate with differences in wall permeability consistent with a recent model for turgor generation by appressoria.

Recombinant Human Growth Hormone (rhGH) Downregulates Hepatocyte Growth Factor (HGF) in Burns

Introduction.Hepatocyte growth factor (HGF) and recombinant human growth hormone (rhGH) have both been shown to increase albumin serum concentrations after major injury. However, the effect of rhGH on HGF production after injury is unknown. We postulated that rhGH effects constitutive protein concentrations by inducing HGF expression.Methods.In order to determine a dose response, 20 male Sprague-Dawley rats received three different concentrations of rhGH 1, 2.5, and 5 mg/kg and a saline treatment. Rats were sacrificed 10 days after burn and serum albumin and HGF plasma concentrations were measured. Eighty male Sprague-Dawley rats received a 60% TBSA third-degree scald burn injury and were randomly divided into three groups, control, burn plus saline treatment, or burn plus rhGH treatment (2.5 mg/kg SQ qD). Rats were sacrificed 2, 5, 7, and 14 days after burn, and serum albumin, plasma, and hepatic tissue HGF concentrations were determined (ELISA, Institute of Immunology, Tokyo, Japan).Results.At 10 days postburn serum albumin levels were significantly increased with rhGH 2.5 mg/kg treatment (P< 0.05); however, HGF plasma concentrations were significantly decreased with a dose of 5 mg/kg of rhGH compared to control and rhGH 1.0 mg/kg (P< 0.05). Serum albumin concentrations decreased immediately after burn and remained low until at least the 14th day after injury. RhGH-treated animals had higher levels of albumin on Day 7 after burn (P< 0.05). Plasma HGF levels decreased immediately after burn, but increased after the second day postburn. Beginning on the 5th day after injury, HGF levels in non-rhGH-treated rats were significantly higher compared to those in rhGH-treated rats (P< 0.05). Hepatic tissue HGF concentrations were higher in non-rhGH-treated rats compared to rhGH treated animals 7 days after burn (P< 0.01).Conclusion.Although rhGH treatment improves constitutive protein synthesis, rhGH decreases HGF concentration in a dose-dependent manner. The improvements in constitutive protein concentrations do not occur via a HGF dependent pathway.

The CIRCE element and its putative repressor control cell cycle expression of the Caulobacter crescentus groESL operon.

The groESL operon is under complex regulation in Caulobacter crescentus. In addition to strong induction after exposure to heat shock, under physiological growth conditions, its expression is subject to cell cycle control. Transcription and translation of the groE genes occur primarily in predivisional cells, with very low levels of expression in stalked cells. The regulatory region of groESL contains both a sigma32-like promoter and a CIRCE element. Overexpression of C. crescentus sigma32 gives rise to higher levels of GroEL and increased levels of the groESL transcript coming from the sigma32-like promoter. Site-directed mutagenesis in CIRCE has indicated a negative role for this cis-acting element in the expression of groESL only at normal growth temperatures, with a minor effect on heat shock induction. Furthermore, groESL-lacZ transcription fusions carrying mutations in CIRCE are no longer cell cycle regulated. Analysis of an hrcA null strain, carrying a disruption in the gene encoding the putative repressor that binds to the CIRCE element, shows constitutive synthesis of GroEL throughout the Caulobacter cell cycle. These results indicate a negative role for the hrcA gene product and the CIRCE element in the temporal control of the groESL operon.

Production and purification of a chitinase from Ewingella americana, a recently described pathogen of the mushroom, Agaricus bisporus

The chitinolytic properties of Ewingella americana, a recently described pathogen of the mushroom, Agaricus bisporus, are reported. E. americana was shown to produce chitinolytic activity in the absence of chitin and in the presence of glucose and N-acetylglucosamine, indicating constitutive synthesis by these strains. A single 33-kDa protein with chitinolytic activity was purified to homogeneity from culture filtrates, by hydrophobic interaction chromatography using a phenyl-group substituted matrix. This enzyme, by virtue of differential activity against chromogenic chitooligosaccharides and against dye-labelled soluble carboxymethylated chitin (CM-chitin-RBV), was demonstrated to be an endochitinase. Our data suggest this 33-kDa chitinase appeared to be the only chitinolytic enzyme produced by E. americana, strains of which do not grow using chitin as a carbon source. The significance of these findings in the context of mushroom disease is discussed.

Retrograde inflammatory signaling from neutrophils to endothelial cells by soluble interleukin-6 receptor alpha.

Endothelial cells initiate the inflammatory response by recruiting and activating leukocytes. IL-6 is not an agonist for this, but we found soluble IL-6 receptor alpha-subunit (IL-6Ralpha), with their constitutive IL-6 synthesis, stimulated endothelial cells to synthesize E-selectin, intracellular adhesion molecule-1, vascular cellular adhesion molecule-1, IL-6, and IL-8, and to bind neutrophils. Neutrophils express significant amounts of IL-6Ralpha and upon stimulation shed it: this material activates endothelial cells through a newly constituted IL-6 receptor. Retrograde signaling from PMN activated in the extravascular compartment to surrounding endothelial cells will recruit more and a wider variety of leukocytes. The limiting signal is a soluble receptor, not a cytokine.

Localization and structure of v-mos in transformed mouse fibroblasts reverted by long-term interferon treatment to nonmalignancy.

We have reported previously that Moloney virus-transformed cells, when treated for over 200 passages in the presence of low concentrations of mouse interferon-alpha/beta, can be reverted to a stable nonmalignant status. The cells recover full contact inhibition and are unable to raise tumors when grafted in nude mice. In the present report, we show that whether reverted or malignant, these cells contain deleted v-mos oncogenes, which have lost 392 nucleotides. The truncated oncogenes contain a reduced and modified open reading frame but are able, however, to induce tumors when transfected in mouse 3T3 cells. As there is no difference either in the location or in the structure of this modified v-mos, whether yielded by reverted or malignant cells, we postulate that both cell lines derive from the same population and this modification does not play any role in the reversion process obtained through prolonged IFN-dependent selection. We suggest that reversion could be an epigenetic phenomenon, involving the constitutive synthesis of IFN-beta only in the reverted and not in the malignant cells. The continued persistence of such noncancerous cells could result at least partly from a balance involving the expression of v-mos, IFN-beta, and an IFN antagonist, sarcolectin. These reverted cells can undergo an unlimited number of passages, but they must be trypsinized before day 5 in confluent cultures. Thereafter, the cells stop dividing, cannot proliferate anymore, progressively show signs of apoptosis, and die.

Antigen presentation by T cells: T cell receptor ligation promotes antigen acquisition from professional antigen‐presenting cells

The purpose of this study was to determine whether the clonotypic specificity of the T cell receptor influences the specificity of T cell-mediated antigen presentation. We have previously shown that myelin basic protein (MBP)-specific Lewis rat GP2.E5/R1 (R1) T cells cultured with antigen, irradiated syngeneic splenocytes (IrrSPL) and tolerogenic monoclonal antibody become highly effective antigen-presenting cells (APC). In the current studies, we investigated the transfer of specific (MBP) and unrelated (conalbumin) antigens from antigen-pulsed SPL to R1 T cells. R1 T cells cultured with IrrSPL that were pulsed simultaneously with both MBP and conalbumin acquired and presented both antigens to the appropriate T cell responders in a secondary assay. These results suggested a physical transfer of major histocompatibility complex (MHC)/peptide complexes from professional APC to R1 T cells. Transfer of conalbumin from professional APC to R1 T cells required specific recognition of MBP and was optimal when both conalbumin and MBP were presented on the same group of professional APC. Antigens transfer did not occur when allogeneic SPL were used as APC. The anti-I-A mAb OX6 inhibited antigen transfer but only when added during the initiation of culture. OX6 also inhibited antigen acquisition by R1-trans, a variant of the R1 T cell line which constitutively synthesizes high levels of I-A, from MBP-pulsed IrrSPL but blockade of I-A did not inhibit antigen acquisition when soluble MBP was added directly to the culture. Despite constitutive synthesis of I-A, R1-trans T cells did not acquire guinea pig MBP from pulsed allogeneic APC. These studies demonstrate that although T cells of a particular specificity can present unrelated antigens, the cognate interaction of the T cell antigen receptor with the appropriate antigen/self-MHC complex strongly promotes acquisition of these complexes from professional APC.

Constitutive Expression, Not a Particular Primary Sequence, Is the Important Feature of the H3 Replacement Variant hv2 in Tetrahymena thermophila

Although quantitatively minor replication-independent (replacement) histone variants have been found in a wide variety of organisms, their functions remain unknown. Like the H3.3 replacement variants of vertebrates, hv2, an H3 variant in the ciliated protozoan Tetrahymena thermophila, is synthesized and deposited in nuclei of nongrowing cells. Although hv2 is clearly an H3.3-like replacement variant by its expression, sequence analysis indicates that it evolved independently of the H3.3 variants of multicellular eukaryotes. This suggested that it is the constitutive synthesis, not the particular protein sequence, of these variants that is important in the function of H3 replacement variants. Here, we demonstrate that the gene (HHT3) encoding hv2 or either gene (HHT1 or HHT2) encoding the abundant major H3 can be completely knocked out in Tetrahymena. Surprisingly, when cells lacking hv2 are starved, a major histone H3 mRNA transcribed by the HHT2 gene, which is synthesized little, if at all, in wild-type nongrowing cells, is easily detectable. Both HHT2 and HHT3 knockout strains show no obvious defect during vegetative growth. In addition, a mutant with the double knockout of HHT1 and HHT3 is viable while the HHT2 HHT3 double-knockout mutant is not. These results argue strongly that cells require a constitutively expressed H3 gene but that the particular sequence being expressed is not critical.

Nitric oxide modulates the acute increase of gastrointestinal transit induced by endotoxin in rats: a possible role for tachykinins.

Because of the evidence that endogenous nitric oxide (NO) plays an essential role in the physiological regulation of gastrointestinal motility we have investigated, by use of the NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), the role of endogenous NO in the acute endotoxin-induced changes of gastrointestinal transit. Pre-treatment with E. coli endotoxin (100 micrograms kg-1, i.v.) induced a significant increase in the gastrointestinal transit of a charcoal suspension in anaesthetized rats. Previous administration of the NO synthase inhibitor, L-NAME (10 mg kg-1, i.v.) significantly prevented the effects of endotoxin. L-arginine (200 mg kg-1, i.v.) and the substance P antagonist [D-Pro2, D-Trp7,9]-substance P (SPA), significantly reversed the effects of L-NAME on gastrointestinal transit in rats treated with endotoxin. Pre-treatment with dexamethasone (5 mg kg-1, s.c., twice), an inhibitor of the expression of inducible NO synthase, did not affect the increase in the gastrointestinal transit through constitutive NO synthesis. The results suggest that constitutive nitric oxide is involved in the increase of gastrointestinal transit induced by endotoxin and that the reduction in transit induced by L-NAME in endotoxin-treated rats is mediated by endogenous tachykinins.

Effects of isoniazid on the proliferation and cytokine production of bladder cancer cells in vitro induced by bacille Calmette-Guérin.

To determine the effects of isoniazid (isonicotinic acid hydrazide), used to reduce the serious side-effects of immunotherapy of superficial bladder cancer with bacille Calmette-Guérin (BCG), on the proliferation and constitutive BCG-induced synthesis of interleukins 6 (IL6) and 8 (IL8) in human bladder cancer cells cultured in vitro. Three poorly differentiated human cell lines, T24, TCC-SUP and BT-B, were used to study the effect of isoniazid on cell proliferation. Cells were inoculated in tissue culture plates and various concentrations of isoniazid added to the medium. Cell density was then monitored for up to 6 days using a colorimetric assay. To determine the effects of isoniazid on constitutive and BCG-induced cytokine synthesis, cells were cultured in medium containing no additions, BCG, isoniazid or BCG with isoniazid, at various concentrations. Samples of medium were collected regularly for 6 h and the cytokine content (IL6 and IL8) determined using enzyme-linked immunosorbent assays. Continuous incubation of proliferating T24, TCC-SUP and BT-B cells with isoniazid at concentrations of 0-100 micrograms/mL did not affect the rate of proliferation. Unlike TCC-SUP and BT-B cells, T24 cells released more IL6 and IL8 during incubation with BCG. At 6 h after the addition of BCG, the cumulative mean (SD) IL6 and IL8 production of T24 cells was 2.6 (0.1) and 2.3 (0.4) ng per 3 x 10(5) cells, compared with a constitutive level of 0.1 (0.0) and 1.3 (0.2) ng, respectively. There was no significant effect of isoniazid (1-100 micrograms/mL) on either the constitutive or BCG-induced synthesis of IL6 and IL8 in T24 cells. Assuming an essential role of (tumour) epithelial cells in the local immune response induced by BCG, these in vitro results suggest that the administration of isoniazid does not interfere with this part of the mechanisms by which BCG operates.

C1Q synthesis by tissue mononuclear phagocytes from normal and from damaged rat liver: Up-regulation by dexamethasone, down-regulation by interferon gamma, and lipopolysaccharide

The subcomponent of complement C1, C1q, mediates complement activation via the classical pathway, and therefore may play an important role in the inflammatory processes in which complement activation is involved. The aim of our study was to investigate C1q synthesis by macrophages of normal and of acutely damaged livers. The localization of C1q in liver tissue was studied by immunohistochemistry. Rat liver tissue macrophages were isolated from normal as well as from acutely damaged (carbon tetrachloride model) liver, and were separated into small, monocyte-like phagocytes and large, mature tissue macrophages, as revealed by immunocytochemistry. C1q gene expression was studied by endogeneous labeling of newly synthesized proteins, immunoprecipitation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and by reverse-transcription polymerase chain reaction (RT-PCR) of C1qB messenger RNA (mRNA). Semiquantitative analysis was performed by Northern blotting of total RNA and hybridization with the radioactively labeled RT-PCR product. C1 esterase inhibitor synthesis was studied in parallel. For comparison, C1q and C1-inhibitor synthesis were also investigated in blood monocytes and peritoneal macrophages. C1q was weakly detectable in sinusoidal cells of the normal liver. C1qB mRNA, as well as constitutive synthesis and secretion of C1q, was clearly detected in freshly isolated and cultured Kupffer cells from normal rat liver. In comparison, newly recruited "inflammatory" macrophages from damaged rat liver synthesized considerably lower amounts of the protein, similar to what was found in the monocyte-like macrophages of normal liver and in peritoneal macrophages. Monocyte C1qB mRNA was not detected even by RT- PCR, and remained undetectable during the time in culture. Similar behavior was observed for C1-inhibitor synthesis. Treatment of the cultures with interferon gamma (IFN-gamma) or lipopolysaccharide (LPS) strongly decreased, whereas treatment with dexamethasone strongly increased C1q gene expression in the macrophage populations, and induced C1qB mRNA in cultured monocytes, as revealed by RT-PCR. Kupffer cells of normal liver may produce considerable amounts of C1q, whereas the inflammatory macrophages of the acutely damaged liver may not be so important for the synthesis of C1q. (Hepatology 1997 Jul;26(1):98-106)

Use of a cyclo-oxygenase type-2-selective non-steroidal anti-inflammatory agent to prevent preterm delivery

Commonly used tocolytics show tachyphylaxis and are associated with potentially life-threatening maternal side-effects. Indometacin is the only drug that has been shown to delay delivery for more than 48 hours in randomised trials,1 but fetal side-effects limit its usefulness.2 Indometacin inhibits the cyclo-oxygenase (COX) enzyme. Of the two COX isoforms, COX-1 is constitutively expressed in tissues with constant prostaglandin synthesis, and COX-2 is inducible and associated with inflammation. COX-2 is upregulated during labour in fetal membranes,3 but constitutive fetal prostaglandin synthesis is probably mediated by COX-1.

Organization and transcription of the myo-inositol operon, iol, of Bacillus subtilis.

Previous determination of the nucleotide sequence of the iol region of the Bacillus subtilis genome allowed us to predict the structure of the iol operon for myo-inositol catabolism, consisting of 10 iol genes (iolA to iouJ); iolG corresponds to idh, encoding myo-inositol 2-dehydrogenase (Idh). Primer extension analysis suggested that an inositol-inducible promoter for the iol operon (iol promoter) might be a promoter-like sequence in the 5' region of iolA, which is probably recognized by sigmaA. S1 nuclease analysis implied that a rho-independent terminator-like structure in the 3' region of iolJ might be a terminator for iol transcription. Disruption of the iol promoter prevented synthesis of the iol transcript as well as that of Idh, implying that the iol operon is most probably transcribed as an 11.5-kb mRNA containing the 10 iol genes. Immediately upstream of the iol operon, two genes (iolR and iolS) with divergent orientations to the iol operon were found. Disruption of iolR (but not iolS) caused constitutive synthesis of the iol transcript and Idh, indicating that the iolR gene encodes a transcription-negative regulator (presumably a repressor) for the iol operon. Northern and S1 nuclease analyses revealed that the iolRS genes were cotranscribed from another inositol-inducible promoter, which is probably recognized by sigmaA. The promoter assignments of the iol and iolRS operons were confirmed in vivo with a lacZ fusion integrated into the amyE locus.

Fructan metabolism in two species of Bromus subjected to chilling and water stress

SUMMARYTwo species of Bromus adapted to different climatic conditions were studied to determine their responses to chilling and water stress. Enzymes of sucrose and fructan metabolism as well as fructoside content were measured in roots and shoots. The results indicate that Bromus pictus (adapted to a cold desert area) has a constitutive fructan synthesis, whilst B. auleticus (adapted to a warmer northern climate) only accumulated fructan under cold stress. Microscopic observations of roots exposed to fluorescent probes ascertained cell viability and showed that the apex of roots in the northern species were more affected by the water‐deficit treatment than the southern species. The presence of fructans in B. pictus and their absence in B. auleticus support the hypothesis that fructans play a role in plant tolerance to environmental stress.

A Model for Quantifying the Contribution of Extracellularly-derived Peptides to Milk Protein Synthesis in the Ruminant Mammary Gland

A model based on the dual-labelled tracer technique of Backwell and co-workers is proposed which allows detailed resolution of isotope dilution data that can be generated by this technique, provided these data are supplemented with appropriate arterio-venous difference and blood flow measurements. The proposed model is constructed and solved in the steady state. Model solution permits, if assumptions are made, calculation of the uptake of an amino acidYfrom the arterial blood supply in both peptide-bound and free form, oxidation ofY, export ofYinto the venous drainage, and synthesis and degradation of milk protein and constitutive tissue protein within the gland. The model provides a means of evaluating the role of amino acids of peptide origin in milk and constitutive protein synthesis in the mammary gland of the lactating ruminant.

Effect of hypoxia on steady-state arachidonic acid metabolism in bovine aortic endothelial cells.

At the onset of acute hypoxia, eicosanoid synthesis by bovine aortic endothelial cells (BAEC) markedly decreases, reflecting a decreased release of arachidonic acid from endogenous stores. To determine the cause of decreased arachidonic acid release, we pulse-labeled BAEC with [14C]arachidonic acid for 5 min under normoxic conditions and chased cells for 1 h under normoxic or hypoxic conditions. The 14C incorporation and specific activity (disintegrations per minute per nanomole) of three major arachidonyl molecular species (16:0-20:4, 18:1-20:4, and 18:0-20:4) of each phospholipid class were determined in cells chased under either of the two conditions. There was no relevant difference between normoxic and hypoxic cells in the metabolism of any of the arachidonyl molecular species of diacyl lipids. However, there was a marked decrease (approximately 40%) in the turnover of arachidonyl alkenylacyl phosphatidylethanolamine in the hypoxic cells. From these results, it appears that the source of arachidonic acid supporting constitutive eicosanoid synthesis in BAEC is alkenylacyl phosphatidylethanolamine and that the limiting enzyme activity determining the rate of eicosanoid synthesis is a plasmalogen-specific phospholipase A2.

Hepatic protein synthesis in the sheep: effect of intake as monitored by use of stable-isotope-labelled glycine, leucine and phenylalanine.

Rates of protein synthesis for the liver, plasma albumin and total plasma protein were quantified in sheep either offered a supra-maintenance intake or fasted for 3 d. The technique of continuous infusion over a 12 h period was employed with the simultaneous infusion of [1-13C]glycine, [1-13C]leucine and [2H5]phenylalanine. Blood and plasma samples were removed at timed intervals from the hepatic portal and hepatic veins plus the aorta. Enrichments of the free amino acids (AA) were determined in all blood and plasma samples as was the protein-bound AA in an apolipoprotein B100 extract. Protein-bound phenylalanine enrichments were also measured in albumin and total protein from plasma plus samples from liver biopsies. The apolipoprotein B100 enrichments agreed well with those of the free AA in hepatic (and hepatic portal) plasma but were lower than for arterial free AA and greater than liver homogenate free AA. This adds support to the concept that export proteins may preferentially use AA directly from extracellular sources. Intake had no significant effect on constitutive liver protein synthesis and the values agreed well with those obtained by other isotopic approaches. There were, however, significant declines, based on hepatic venous free phenylalanine enrichment, at the lower intake in both the fractional (3.4 v. 4.7% per d; P = 0.024) and absolute (2.4 v. 4.2 g/d; P = 0.011) synthesis rates of albumin, which matched the estimated decrease in total plasma albumin content (52 v. 67 g, P < 0.01). In contrast, there was a smaller reduction in total plasma protein mass (145 v. 151 g, P = 0.035) with no observed significant difference in kinetic parameters. Albumin synthesis was calculated to account for a maximum of 17% of total liver protein synthesis in the fed condition and this may fall to 8% during moderate fasts.

A role for cpeYZ in cyanobacterial phycoerythrin biosynthesis.

Pigment mutant strain FdR1 of the filamentous cyanobacterium Fremyella diplosiphon is characterized by constitutive synthesis of the phycobiliprotein phycoerythrin due to insertional inactivation of the rcaC regulatory gene by endogenous transposon Tn5469. Whereas the parental strain Fd33 harbors five genomic copies of Tn5469, cells of strain FdR1 harbor six genomic copies of the element; the sixth copy in FdR1 is localized to the rcaC gene. Electroporation of FdR1 cells yielded secondary pigment mutant strains FdR1E1 and FdR1E4, which identically exhibited the FdR1 phenotype with significantly reduced levels of phycoerythrin. In both FdR1E1 and FdR1E4, a seventh genomic copy of Tn5469 was localized to the cpeY gene of the sequenced but phenotypically uncharacterized cpeYZ gene set. This gene set is located downstream of the cpeBA operon which encodes the alpha and beta subunits of phycoerythrin. Complementation experiments correlated cpeYZ activity to the phenotype of strains FdR1E1 and FdR1E4. The predicted CpeY and CpeZ proteins share significant sequence identity with the products of homologous cpeY and cpeZ genes reported for Pseudanabaena sp. strain PCC 7409 and Synechococcus sp. strain WH 8020, both of which synthesize phycoerythrin. The CpeY and CpeZ proteins belong to a family of structurally related cyanobacterial proteins that includes the subunits of the CpcE/CpcF phycocyanin alpha-subunit lyase of Synechococcus sp. strain PCC 7002 and the subunits of the PecE/PecF phycoerythrocyanin alpha-subunit lyase of Anabaena sp. strain PCC 7120. Phycobilisomes isolated from mutant strains FdR1E1 and FdR1E4 contained equal amounts of chromophorylated alpha and beta subunits of phycoerythrin at 46% of the levels of the parental strain FdR1. These results suggest that the cpeYZ gene products function in phycoerythrin synthesis, possibly as a lyase involved in the attachment of phycoerythrobilin to the alpha or beta subunit.

P52PAI-1 gene expression in butyrate-induced flat revertants of v-ras-transformed rat kidney cells: mechanism of induction and involvement in the morphological response.

Sodium n-butyrate-induced flat reversion in v-K-ras oncogene-transformed rat kidney (KNRK) cells is associated with transcriptional activation of the p52PAI-1 gene (which encodes the type-1 inhibitor of plasminogen activator). Butyrate-initiated expression of p52PAI-1 mRNA and protein correlated with induced cell spreading and preceded development of cell-to-substrate focal adhesions. Such undersurface matrix contact structures, which are absent from parental KNRK cells, require proximal PAI-1 deposition for their stabilization. Stimulated p52PAI-1 expression by flat revertants (approximating 25-fold that of control cells) and the accompanying cytoarchitectural reorganization appeared to be programmed responses to butyrate as both events required de novo RNA and protein synthesis, metabolic characteristics consistent with a secondary pathway of gene regulation. To assess the relevance of p52PAI-1 induction to the process of flat reversion more critically, a molecular genetic approach was designed to maintain high-level constitutive p52PAI-1 synthesis in the absence of butyrate. KNRK cells transfected with a Rc/CMVPAI plasmid construct, in which expression of a p52PAI-1 cDNA insert was driven by enhancer-promoter sequences from the immediate-early gene of human cytomegalovirus, formed colonies comprised of flat-revertant-like cells with a greater frequency than did cells transfected with the Rc/CMV vector alone (24.8% and 1.7% respectively). Comparative analysis of randomly selected Rc/ CMVPAI clones indicated that a 10-fold increase in immunoreactive p52PAI-1 protein, relative to Rc/CMV isolates, correlated with generation of the flat phenotype. These data suggest that induced p52PAI-1 expression probably functions in the development of morphological revertants in the KNRK cell system.

Constitutive synthesis of heat shock protein (72 kD) in human peripheral blood mononuclear cells: implications for use as a clinical test of recent thermal stress

There is no clinical laboratory marker to enhance the diagnosis of recent thermal stress in humans. The 72 kD heat shock protein, HSP 72, which is rapidly synthesized after heat stress could be useful in the diagnosis of illnesses associated with heat stress. In humans HSP, 72 is rapidly synthesized after thermal stress; however, conflicting data suggest it may also undergo low level constitutive synthesis. If HSP 72 is constitutively synthesized, a semi-quantitative test will be necessary to detect recent heat stress; if not, a qualitative test would be sufficient, peripheral blood mononucler cells were chosen for this investigation because they can be isolated from a small sample (clinically acceptable) of blood. Following heat stress Western analysis and autoradiography of one- and two-dimensional electrophoresis samples demonstrated low levels of HSP 72 in unstressed cells. HSP 72 increased with heat stress, and remained elevated for up to 48 h. HSP 72 mRNA was detectable in small amounts in nonheat stressed cells. Heat stress increased HSP 72 mRNA 1 and 2 h after stress and remained elevated for 6 h. HSP 72 persists long enough to be potentially useful as a diagnostic probe of recent heat injury; however, a semi-quantitative assay will be necessary.