A heterotrimeric G protein, G alpha i-3, on Golgi membranes regulates the secretion of a heparan sulfate proteoglycan in LLC-PK1 epithelial cells.

A heterotrimeric G alpha i subunit, alpha i-3, is localized on Golgi membranes in LLC-PK1 and NRK epithelial cells where it colocalizes with mannosidase II by immunofluorescence. The alpha i-3 was found to be localized on the cytoplasmic face of Golgi cisternae and it was distributed across the whole Golgi stack. The alpha i-3 subunit is found on isolated rat liver Golgi membranes by Western blotting and G alpha i-3 on the Golgi apparatus is ADP ribosylated by pertussis toxin. LLC-PK1 cells were stably transfected with G alpha i-3 on an MT-1, inducible promoter in order to overexpress alpha i-3 on Golgi membranes. The intracellular processing and constitutive secretion of the basement membrane heparan sulfate proteoglycan (HSPG) was measured in LLC-PK1 cells. Overexpression of alpha i-3 on Golgi membranes in transfected cells retarded the secretion of HSPG and accumulated precursors in the medial-trans-Golgi. This effect was reversed by treatment of cells with pertussis toxin which results in ADP-ribosylation and functional uncoupling of G alpha i-3 on Golgi membranes. These results provide evidence for a novel role for the pertussis toxin sensitive G alpha i-3 protein in Golgi trafficking of a constitutively secreted protein in epithelial cells.

Insulin-induced desensitization at the receptor and postreceptor level in mitogen-activated human T-lymphocytes.

Human T-lymphocytes activated by phytohemagglutin acquire insulin receptors in culture. Saturation analysis of insulin-binding activity in the presence of competing ligand revealed curvilinear Scatchard plots. Insulin receptors were not regulated by insulin before mitogen activation and culture of T-lymphocytes. However, insulin-induced downregulation of insulin receptors was: (1) demonstrable in receptor-positive cells, (2) dependent on insulin concentration, (3) temporally unrelated to insulin internalization, and (4) prevented by culture at 4 degrees C but not by cycloheximide at 37 degrees C. Recovery of insulin receptors required further culture of cells in media depleted of insulin for 24 h. Scatchard analysis revealed loss of receptor number without changes in receptor affinity. Insulin-induced increases in glucose transport and oxidation were demonstrable in receptor-positive cells but not in receptor-negative cells. However, these effects were extremely time-dependent. After a 2-h exposure of cells to 10(-8) M insulin, increases in glucose transport were no longer demonstrable. Elution of bound insulin from these cells followed by re-exposure to insulin depressed glucose transport in them. Recovery from this hyporesponsive, desensitized state required a 6-h culture in insulin-depleted media. Glucose oxidation of desensitized cells could be stimulated by spermine but not by insulin. These studies demonstrate the activated human T-lymphocyte is an insulin-sensitive tissue that is capable of limiting its physiologic response to insulin by receptor- and postreceptor-mediated mechanisms.

Dual inhibition of REV-ERBß and autophagy as a novel pharmacological approach to induce cytotoxicity in cancer cells.

REV-ERBα and REV-ERBß nuclear receptors regulate several physiological processes, including circadian rhythm and metabolism. A previous study reported the REV-ERBα gene to be co-overexpressed with ERBB2 in breast cancer cell lines. Surprisingly, we found that several tumor types, including a number of breast cancer cell lines, predominantly express the REV-ERBß variant. This pattern was independent of ERBB2 and ER status, and opposite to that of non-cancer mammary epithelial HMEC cells, in which REV-ERBα was the major variant. Consistent with this molecular profile, REV-ERB target genes in both circadian and metabolic pathways were derepressed upon silencing of REV-ERBß, but not REV-ERBα. Strikingly, we found that REV-ERBß is a determinant of sensitivity to chloroquine, a clinically relevant lysosomotropic agent that suppresses autophagy. The cytoprotective function of REV-ERBß appears to operate downstream of autophagy blockade. Through compound screening, we identified ARN5187, a novel lysosomotropic REV-ERBß ligand with a dual inhibitory activity toward REV-ERB-mediated transcriptional regulation and autophagy. Remarkably, although ARN5187 and chloroquine share similar lysosomotropic potency and have a similar effect on autophagy inhibition, ARN5187 is significantly more cytotoxic. Collectively, our results reveal that dual inhibition of REV-ERBß and autophagy is an effective strategy for eliciting cytotoxicity in cancer cells. Furthermore, our discovery of a novel inhibitor compound of both REV-ERB and autophagy may provide a scaffold for the discovery of new multifunctional anticancer agents.

Recurrent thrombotic microangiopathy in a renal allograft. Case report and review of the literature.

Thrombotic microangiopathy in a renal allograft may either reflect a recurrence of the patient's original disease, i.e., thrombotic thrombocytopenic purpura, hemolytic-uremic syndrome, or more commonly may be a manifestation of allograft rejection. This report describes a patient in whom irreversible renal failure developed during thrombotic thrombocytopenic purpura. Two years later while her condition was in clinical remission, she received a 2 DR-matched cadaveric allograft. Nineteen days following transplantation, thrombotic microangiopathy developed in the graft with eventual loss of allograft function despite vigorous plasmapheresis therapy. Multiple factors in addition to possible recurrent disease that may have contributed to this event were identified. The literature on thrombotic microangiopathy and renal transplantation is reviewed.

Tunicamycin blocks the emergence and maintenance of insulin receptors on mitogen-activated human T lymphocytes.

Treatment of phytohemagglutinin (PHA) activated human T lymphocytes with tunicamycin, an antibiotic that specifically inhibits asparagine-linked N-glycosylation of proteins, totally blocked the normal emergence of insulin receptors on these lymphocytes and their cellular proliferation during culture in a dose-dependent manner. Carbohydrate incorporation into protein was inhibited 82% by 0.5 microgram/mL while leucine incorporation was unaffected. Tunicamycin exposure of activated T lymphocytes, which had acquired insulin receptors during culture, reduced cellular insulin binding by 35% to 84% and reduced PHA binding to 40% of control levels within 24 hours. Scatchard analysis revealed decreases in insulin binding capacity but not affinity. Similar treatment with cycloheximide only decreased insulin binding by 12%. These findings suggest N-glycosylation of proteins is a necessary biochemical event (1) for the emergence and maintenance of insulin receptors on mitogen activated T lymphocytes, and (2) for mitogen activated T lymphocytes to undergo cell division.

Multiple insulin-responsive elements regulate transcription of the GAPDH gene.

Multiple elements in the upstream region of the GAPDH gene play a role in mediating the acute and chronic effect of insulin on GAPDH gene expression. The complexity of this regulation provides many layers of control. In differentiated tissues, the transcriptional response to insulin results from the additive effects of g/TRE, IRE-A and IRE-B. The gTRE may interact with newly synthesized c-fos/c-jun heterodimer to activate GAPDH gene transcription. Studies are underway to determine whether protein synthesis inhibitors affect the regulation of GAPDH. Because there are several elements that mediate the effect, it will be difficult to determine the significance of these findings until each cis-acting factor and its binding protein can be studied in isolation. IRE-A and IRE-B act together to promote a 5- to 8-fold insulin effect on HGAPDH-CAT in H35 hepatoma cells and a 3-fold effect in 3T3 adipocytes. We have succeeded in detecting an insulin-sensitive DNA-binding protein referred to as IREA-BP with an element -480 to -435. Insulin treatment of differentiated 3T3 adipocytes for 1 hr results in a 4-fold increase in the amount of this binding protein, as estimated by the amount of 32P-labelled oligonucleotide retarded on non-denaturing PAGE (11). The effect of insulin on IRP-B is comparable. Furthermore, IREA-BP is induced during the process of fasting and refeeding rats, an important in vivo correlate with our tissue culture models (11). These observations imply that the binding proteins IREA-BP and IRP-B are essential components in the signal transduction pathway of insulin action on GAPDH gene expression in metabolically active tissues such as fat and liver. Differentiation-dependence and tissue-specificity are achieved through multiple regulatory elements and involve pre- and post-translational regulation of multiple transcription factors. IREA-BP is present in preadipocytes but activity in highly induced upon differentiation of preadipocytes to adipocytes. The IRE-B (-408 to -269) DNA binding protein is not detected in 3T3 preadipocytes. A gC/EBP like-protein takes part in the formation of this complex which may explain the inductive effect of differentiation on binding. Finally, footprint and cotransfection studies indicate that the differentiation-dependent protein C/EBP also regulates GAPDH gene transcription through a motif located within one hundred nucleotides of the promoter. We have begun to clone the IRE-A and IRE-B DNA binding proteins. An IRE-A binding protein that footprints the 3' domain of the IRE-A has been cloned.(ABSTRACT TRUNCATED AT 400 WORDS)

The third kidney transplant.

To determine the feasibility of third kidney transplantation, the experience at the University of Iowa was evaluated. The success of 14 such transplantations was dependent on the outcome of both of the previous graft operations. Three successful third transplantations with graft survival of 6 years, 3 years, and 1 year have occurred in recipients with more than 1 year survival of a previous kidney. Conversely, graft loss due to rejection developed in all patients who experienced graft survival of less than 1 year for both antecedent grafts. Moreover, HLA-A and -B matching and level of presensitization were not predictive of success in this series. These data suggest that third kidney transplantation using conventional immunosuppression may not be appropriate in the subgroup of patients who have clearly lost their first two grafts to early rejection.

Fibromuscular dysplasia: an unusual cause of hypertension in the transplant recipient.

A transplant recipient developed hypertension from unsuspected fibromuscular dysplasia of the donor renal artery. We believe this is the first reported case of this disease transmitted by transplantation. Successful repair of the stenosis was obtained by resection of the stenotic area and reanastomosis to the internal iliac artery. While the diagnosis of fibromuscular hyperplasia was not suspected in our donor prior to organ retrieval, its eventual occurrence in the transplanted kidney suggests that when the donor clinical picture is appropriate the lesion should be searched for prior to use of the organs.

Decreased mitogen activated protein kinase activities in congenital diaphragmatic hernia-associated pulmonary hypoplasia.

BACKGROUND/PURPOSE: The mechanisms that cause pulmonary hypoplasia associated with congenital diaphragmatic hernia (CDH) currently are unknown. The authors proposed that the reduced size and immaturity of these lungs may be associated with differences in the levels of mitogen activated protein (MAP) kinase phosphorylation (extracellular signal regulated protein kinases, ERK-1 and -2). METHODS: ERK-1 activities were measured using immune-complex kinase assays on fetal whole-lung lysates obtained from both nitrofen and olive oil-treated (control) pregnant rats. In addition, ERK-1 and ERK-2 functional activities were estimated by semiquantitative Western blot analysis, using an antibody specific for the diphosphorylated (dp-ERK, activated) forms of the enzymes. RESULTS: ERK-1 activities, measured using immune-complex kinase assays, were reduced in CDH lungs compared with olive oil-treated controls (P <.02). In addition, dp-ERK-1 and dp-ERK-2 levels were found to be reduced in CDH lungs compared with controls (dp-ERK-1, P =.003; dp-ERK-2, P =.04), whereas ERK-1 and ERK-2 protein levels were unchanged. CONCLUSIONS: The lower values of ERK-1 activity and reduced amounts of dp-ERK-1 and dp-ERK-2 in lung tissue from CDH animals, suggests that ERK-1 and ERK-2 activities are reduced in pulmonary hypoplasia associated with CDH. The observed reduction in ERK-1 and ERK-2 activities implicates attenuated cell signaling upstream of the ERK-1 and -2 enzymes.

The cardiovascular work of competitive dinghy sailing.

BACKGROUND: Hiking is the special manoeuvre, which the dinghy sailor uses to counterbalance the capsizing effect of the wind on the boat. In the present research the work required of the heart by this exercise was studied in the laboratory using a boat simulator. METHODS: Seven Laser male sailors selected from those in the first places in the junior national rank participated in this study. Their endurance, at different levels of isometric hiking efforts, was measured. Energy expenditure due to hiking was estimated from measurements of oxygen consumption, carbon dioxide elimination and blood lactate concentration. The cardiac load was evaluated by measuring blood pressure using the conventional method and heart rate measured by electrocardiography. Cardiac output was measured using the CO2 re-breathing method. Left ventricular work was then calculated as cardiac output multiplied by mean arterial pressure. RESULTS: The most relevant result was that, while whole body cost of hiking was relatively low (about 1 IO2 min-1), the power of the heart was very significant: cardiac output almost doubled with respect to that at rest and arterial mean pressure rose from 12.5 kPa (rest) to 18.5 kPa (hiking). Thus, left ventricular power rose from 1.2 Watt to 3.2 Watt, which is a typical cardiovascular response to muscular isometric contraction. CONCLUSIONS: These results assume relevance when a person's eligibility for sailing sports is evaluated.

Metabolic and morphologic effects of colchicine on human T-lymphocyte expression of Fc mu and Fc gamma receptors.

The influence of colchicine on human T-cell Fc mu- and Fc gamma-receptor expression during culture was studied utilizing a rosette technique with bovine erythrocytes coated with IgM (EOx-IgM) or IgG (EOx-IgG). Treatment of T cells with greater than or equal to 10(-6) M concentrations of colchicine induced in these cells progressive loss of microtubules and surface microvilli, inhibited their Fc mu-, but not Fc gamma-receptor expression during culture, and increased their cyclic AMP levels. However, similar treatment of cells with lumicolchicine, a photoinactivated isomer, identically inhibited the T-cell Fc mu-receptor expression as well, without inducing loss of microtubules or microvilli or raising cyclic AMP levels in them. A direct influence on T-cell protein synthesis by either colchicine or lumicolchicine is likely, as greater than or equal to 10(-6) M concentrations of alkaloid identically inhibited [3H]leucine incorporation and Fc mu-receptor expression by T cells without inhibiting their alpha-methyl isobutyric acid transport. No impairment of optimal EOx-IgM rosette formation occurred in control T lymphocytes cultured for 24 hr and then treated with colchicine, which suggests that its effects did not directly influence the receptor-ligand interaction itself. These findings suggest colchicine has several sites of action on T cells, dependent and independent of microtubular depolymerization, which may be responsible for alterations of T-lymphocyte cellular metabolism and function.

Isolation and complete sequence of a functional human glyceraldehyde-3-phosphate dehydrogenase gene.

Glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.2.12) (GAPDH) mRNA levels, protein, and enzymatic activity increase in 3T3-F442A adipocytes after exposure to physiological concentrations of insulin (Alexander, M., Curtis, G., Avruch, J., and Goodman, H. (1985) J. Biol. Chem. 260, 11978-11985). In order to understand the mechanism of this regulation, we have isolated and sequenced 5.4 kilobase pairs of a 12-kilobase pair human genomic clone encoding a functional GAPDH gene. The gene consists of 9 exons and 8 introns with eukaryotic signals necessary for the transcription and translation of GAPDH mRNA. The exon sequence confirms previously published cDNA sequences for human GAPDH in muscle, liver, and erythrocytes. The organization of the human and the unique chicken GAPDH genes is strikingly similar. Although chicken exons VIII-XI have been fused into human exon 8, introns which separate exons encoding the NAD binding, catalytic, and helical domains of the GAPDH protein have been retained. Stable transfection of rodent cells with the intact human GAPDH gene resulted in the expression of a correctly initiated human GAPDH mRNA and an enzymatically active human GAPDH polypeptide. Thus, the gene contains a functional promoter and intact coding sequences. Although many processed GAPDH pseudogenes and GAPDH-like sequences are present in the human genome, Southern blot analysis of human genomic DNA using a probe derived from the 3'-untranslated region of the GAPDH gene detected only two genes, a 10-copy processed pseudogene and a single copy of the isolated gene. In contrast, a probe derived from an intron segment of the isolated gene detected only a single copy of the GAPDH gene. Collectively, these findings strongly suggest that the human genome encodes a single functional GAPDH gene.

Properties and regulation of the T lymphocyte insulin receptor.

Primary human T lymphocytes that have been mitogen activated in chemically defined medium express cell surface insulin receptors. The receptor is identical to other mammalian insulin receptors in binding properties, including: pH dependency, ligand affinity, hormone specificity, and cooperative interactions. Scatchard plots are curvilinear and a ligand-induced increase in dissociation, the property normally associated with "negative cooperativity", is kinetically demonstrable. In vitro insulin treatment of the receptor-negative, resting T lymphocyte slightly enhances the degree of insulin binding which emerges following cellular activation. Insulin treatment of receptor-positive lymphoblasts results in insulin receptor "down-regulation". These findings indicate that T lymphoblast insulin receptor concentrations are not significantly influenced by insulin before their emergence but are dramatically regulated by insulin following their appearance at the cell surface.

Demonstration of receptors for insulin-like growth factor-II on human T-lymphocytes.

Primary human T-lymphocytes that have been mitogen activated in chemically defined medium demonstrate cell surface receptor for insulin-like growth factor-II (IGF-II). In contrast resting T-lymphocytes demonstrate little or no IGF-II receptor. Receptors appear within 24 hours of mitogen activation with maximal binding occurring at 72 hours. After this point IGF-II binding declines. Receptor binding of IGF-II to T-lymphocytes does not show a sharp pH dependence but is maximal above pH 7. Insulin does not compete for IGF-II binding sites and proinsulin competes only weakly, suggesting that this is a type 2 IGF receptor and not an insulin receptor. Furthermore, anti-insulin antibodies do not inhibit IGF-II from binding to activated T-lymphocytes indicating divergent binding domains on the two peptide hormones. IGF-II demonstrates stimulating action on T-lymphocyte proliferation probably mediated by binding of IGF-II to this receptor.

cAMP regulates G-protein alpha i-2 subunit gene transcription in polarized LLC-PK1 cells by induction of a CCAAT box nuclear binding factor.

Heterotrimeric G-proteins function as signal transducers for a variety of hormone-coupled enzyme systems in eukaryotic cells. In LLC-PK1 renal cells, vasopressin-stimulated adenylylcyclase activity is regulated in part, by the counterbalancing activity of stimulatory G-proteins (Gs) and inhibitory pertussis toxin-sensitive G-proteins (Gi). Two Gi genes encoding the Gi isoforms G alpha i-2 and G alpha i-3 are expressed in LLC-PK1 cells. In polarized cells, these isoforms are topographically segregated to different membranes, which allows for the selective inhibition of adenylylcyclase by G alpha i-2. The genes encoding these isoforms are similarly regulated in these cells during growth and differentiation but differ in response to steroid hormone signals (Holtzman, E.J., Kinane, T.B., West, K., Soper, B.W., Karga, H., Ausiello, D.A., and Ercolani, L. (1993) J. Biol. Chem. 268, 3964-3975). We now demonstrate after stimulating polarized LLC-PK1 cells with forskolin, which raises intracellular cAMP levels 50-fold, G alpha i-2 but not G alpha i-3 protein is increased 3-fold at 12 h and remains elevated above control values by 24 h. In cells stably transfected with G alpha i-2 or G alpha i-3 gene 5'-flanking sequences fused to firefly luciferase cDNA reporter gene, forskolin treatment increased G alpha i-2 transcription 3-fold but inhibited G alpha i-3 transcription by 50% at 12 h. In vivo footprinting of forskolin-treated cells was performed to examine the molecular basis for activation of the G alpha i-2 gene. Protected guanosines were identified in a 135-base pair (bp) area previously associated with enhancer activity of this gene in non-polarized cells. This DNA segment did not contain the classical cAMP response element 5'-TGACGTCA-3'. Utilizing the 135-bp DNA segment as a probe in mobility shift assays, which compared nuclear extracts from cells before and after forskolin treatment, an induced nuclear protein complex was identified. Following systematic reduction and mutation of this DNA segment, a "CCAAT" box motif was identified that bound the induced nuclear protein complex during forskolin-induced G alpha i-2 gene transcriptional activation. Induction of this nuclear protein complex was prevented in forskolin-treated cells by cycloheximide. To demonstrate functional activity of the CCAAT box motif, cells were transiently transfected with plasmids encoding either the minimal 135-bp segment or a multimerized CCAAT box segment fused to a Rous sarcoma minimal promoter/firefly luciferase reporter gene.(ABSTRACT TRUNCATED AT 400 WORDS)

Regulation of the G-protein alpha i-2 subunit gene in LLC-PK1 renal cells and isolation of porcine genomic clones encoding the gene promoter.

Heterotrimeric G-proteins function as signal transducers for a variety of hormone-coupled enzyme and ion transport systems in eukaryotic cells. We have studied G-protein-coupled processes that appear to be developmentally regulated in polarized pig kidney cells (LLC-PK1). Following trypsinization, LLC-PK1 cells differentiate from a rounded cell type to a fully polarized epithelium by 7 days of culture. During this differentiation, the expression of G-protein alpha i-2 subunit mRNA was not detected until day 4 of culture, it peaked at day 6, and declined thereafter. In contrast, G-protein alpha s subunit mRNA which peaked on day 4 was easily detected on all culture days. The presence of the alpha i-2 protein on epithelial cell basolateral membranes followed the same pattern of mRNA expression during culture. To understand the developmental expression of the alpha i-2 subunit in non-polarized cells and its potential regulation by hormones and second messengers in polarized cells at the transcriptional level, genomic DNA segments encoding the alpha i-2 gene promoter were isolated from an EMBL-3 porcine genomic library. S1 nuclease analysis of LLC-PK1 mRNA with cRNA probes derived from these DNA segments revealed major and a minor transcriptional start sites 131 and 171 base pairs upstream of the translation initiation site. The porcine and human alpha i-2 subunit genes shared a 78% sequence identity in their 5' flanks which suggested an evolutionary conservation of cis elements required to influence their transcription. The porcine alpha i-2 gene promoter was identified by fusing DNA segments encoding putative 5'-flanking areas of the gene to a plasmid that contained a firefly luciferase reporter gene but lacked a promoter. The minimal promoter was found between -130 and -60 base pairs from the major transcription start site. No typical "TATA-like" sequences were found. However, a "GC" box and a "TGTGG" sequence were two potential cis elements required for basal transcription of the porcine gene promoter which shared a 76% sequence identity to the promoter of another GTP-binding protein, the human c-Ha-ras proto-oncogene. Transcription of the gene was inhibited following treatment of renal cells with 10(-8) M dexamethasone.(ABSTRACT TRUNCATED AT 400 WORDS)

Colocalization of GAPDH and band 3 (AE1) proteins in rat erythrocytes and kidney intercalated cell membranes.

Glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.2.12) (GAPDH) is a multifunctional protein that associates with the cytoplasmic face of intact human erythrocyte membranes. This association has been postulated to be critically dependent on the interaction of GAPDH with the highly acidic NH2-terminal domain of the principal integral membrane protein of the erythrocyte plasma membrane, the band 3 anion exchanger (AE1). This domain is not conserved in murine erythrocyte AE1 and is fully deleted in the alternatively spliced AE1 isoform that is expressed in the kidney. The lack of conservation of this domain has been proposed to explain the reported absence of GAPDH association with rodent erythrocyte membranes. To determine whether GAPDH could be associated with AE1 proteins in rodent cell membranes, specific rabbit antibodies to peptide sequences of rat GAPDH and mouse AE1 were used to immunolocalize these proteins in sequential semithin sections of rat erythrocytes and kidney medulla. In rat erythrocytes, GAPDH immunoreactivity was predominantly membrane associated and colocalized with AE1. In the kidney medulla, GAPDH was concentrated in the basolateral membrane of type A intercalated cells, where it colocalized with the alternatively spliced kidney form of AE1. GAPDH immunoreactivity was not detected in the plasma membrane of any other cell type in the kidney, indicating its predominant association with AE1-rich membranes. If this membrane interaction occurs via AE1 binding, then GAPDH must have binding sites in addition to those previously described for such binding in human AE1.

Identification of a core motif that is recognized by three members of the HMG class of transcriptional regulators: IRE-ABP, SRY, and TCF-1 alpha.

Insulin induces glyceraldehyde-3-phosphate dehydrogenase (GADPH) gene transcription in part by regulating one or more proteins that bind a cis-acting element, IRE-A. We have recently cloned a protein, IRE-ABP, that binds the IRE-A element. IRE-ABP is a member of the HMG class of transcriptional regulators and is 67% identical within its HMG box domain to the candidate gene for the testis-determining factor, SRY. IRE-ABP and SRY share binding specificity for the IRE-A motif. This sequence is also highly conserved with a core motif, 5'-Py-ctttg(a/t)-3', contained in T-cell specific genes that have high affinity for TCF-1 alpha, another member of the HMG class of transcriptional regulators. Thus, diverse members of the HMG family interact with similar nucleotide sequences to regulate expression of genes that initiate and maintain the differentiated phenotype. We have found this core motif in the upstream region of many genes that are positively and negatively regulated by insulin. These observations suggest that IRE-ABP or a related family member may coordinate the expression of these genes. The HMG family of proteins has diverse functions ranging from the regulation of differentiation and mating type in yeast to the regulation of tissue- and species-specific gene expression in mammals. Insulin regulates GAPDH gene transcription in a tissue-specific manner. We propose that members of the IRE-ABP family play an important role in controlling tissue specificity of the insulin response.

Induction and amplification of T-lymphocyte proliferative responses to periodate and soybean agglutinin by human adult vascular endothelial cells.

Human mononuclear phagocyte (M phi) populations were compared to adult human endothelial cells (HEC) for their respective abilities to influence the proliferative responses of purified human T lymphocytes to the mitogenic agents Na-m-periodate (IO-4), soybean agglutinin (SBA), or allogeneic cells. HEC and M phi were both capable of inducing proliferative responses of allogeneic T lymphocytes in mixed-lymphocyte culture. Under low cell density culture conditions, purified T-lymphocyte proliferative responses to IO-4 or SBA could be restored by addition of syngeneic M phi or HEC. At higher cell density culture conditions, proliferation of T cells to IO-4 could be amplified more by HEC than M phi. T-lymphocyte proliferative responses to SBA were amplified by addition of HEC but were suppressed by addition of M phi. These findings indicate that human adult HEC are unique and potent accessory cells for T lymphocytes. Furthermore, these findings demonstrate that accessory cell functions of HEC can be discriminated from those of M phi.