Showing papers by "University of Texas Southwestern Medical Center published in 1990"
TL;DR: The mevalonate pathway produces isoprenoids that are vital for diverse cellular functions, ranging from cholesterol synthesis to growth control, and could be useful in treating certain forms of cancer as well as heart disease.
Abstract: The mevalonate pathway produces isoprenoids that are vital for diverse cellular functions, ranging from cholesterol synthesis to growth control. Several mechanisms for feedback regulation of low-density-lipoprotein receptors and of two enzymes involved in mevalonate biosynthesis ensure the production of sufficient mevalonate for several end-products. Manipulation of this regulatory system could be useful in treating certain forms of cancer as well as heart disease.
5,125 citations
TL;DR: It is established that B27 plays a central role in the pathogenesis of the multi-organ system processes of the spondyloarthropathies and elucidation of the role of B27 should be facilitated by this transgenic model.
1,133 citations
TL;DR: At present it appears that carbohydrates and monounsaturated fatty acids represent the preferred replacements for saturated fatty acids, although modest increases in polyunsaturated fatty acid and stearic acid, at the expense of cholesterol-raising saturates, probably are safe and may provide for greater variety in the diet.
1,048 citations
TL;DR: A review of published data revealed NPXY sequences in cytoplasmic domains of at least 10 other cell surface proteins, including tyrosine kinase-linked receptors of the epidermal growth factor and insulin receptor family, the beta-subunits of three integrin receptors, and the amyloid A4 precursor protein.
952 citations
TL;DR: The enzyme was purified approximately 60,000-fold from rat brain cytosol through use of a chromatography step based on the enzyme's ability to bind to a hexapeptide containing the consensus sequence (Cys-AAX) for farnesylation.
819 citations
TL;DR: The structure and properties of p65 suggest that it may have a role in mediating membrane interactions during synaptic vesicle exocytosis, and a novel homology between a cellular protein and the regulatory domain of protein kinase C is reported.
Abstract: NEUROTRANSMITTERS are released at synapses by the Ca2+-regulated exocytosis of synaptic vesicles, which are specialized secretory organelles that store high concentrations of neurotransmitters1,2. The rapid Ca2+-triggered fusion of synaptic vesicles is presumably mediated by specific proteins that must interact with Ca2+ and the phospholipid bilayer. We now report that the cytoplasmic domain of p65, a synaptic vesicle-specific protein3 that binds calmodulin4 contains an internally repeated sequence that is homologous to the regulatory C2-region of protein kinase C (PKC)5. The cytoplasmic domain of recombinant p65 binds acidic phospholipids with a specificity indicating an interaction of p65 with the hydrophobic core as well as the headgroups of the phospholipids. The binding specificity resembles PKC, except that p65 also binds calmodulin, placing the C2-regions in a context of potential Ca2+-regulation that is different from PKC. This is a novel homology between a cellular protein and the regulatory domain of protein kinase C. The structure and properties of p65 suggest that it may have a role in mediating membrane interactions during synaptic vesicle exocytosis.
799 citations
706 citations
TL;DR: A protein kinase characterized by its ability to phosphorylate microtubule-associated protein-2 (MAP2), is thought to be an early intermediate in an insulin-stimulated phosphorylation cascade and in a variety of other mammalian cell responses to extracellular signals.
Abstract: A protein kinase characterized by its ability to phosphorylate microtubule-associated protein-2 (MAP2), is thought to be an early intermediate in an insulin-stimulated phosphorylation cascade and in a variety of other mammalian cell responses to extracellular signals. A complementary DNA that encodes this protein serine-threonine kinase has been cloned, and the protein designated extracellular signal-regulated kinase 1 (ERK1). ERK1 has striking similarity to two protein kinases, KSS1 and FUS3, from yeast. The yeast kinases function in an antagonistic manner to regulate the cell cycle in response to mating factors. Thus, ERK1 and the two yeast kinases constitute a family of evolutionarily conserved enzymes involved in regulating the response of eukaryotic cells to extracellular signals.
687 citations
TL;DR: The three-dimensional structure of tumor necrosis factor (TNF-alpha), a protein hormone secreted by macrophages, has been determined and striking structural homology to several viral coat proteins, particularly satellite tobacco necrosis virus is revealed.
609 citations
TL;DR: Findings suggest that nucleotide exchange on G proteins is regulated by the presentation of multiple cationic structures on the inner face of the plasma membrane.
587 citations
TL;DR: It is found that cholesterol plays a critical role in maintaining the caveola membrane domain and modulates the interaction of GPI-anchored membrane proteins via their phospholipid anchors.
Abstract: The folate receptor is a glycosyl-phosphatidylinositol (GPI)-anchored membrane protein that mediates the delivery of 5-methyltetrahydrofolate to the cytoplasm of MA104 cells. Ordinarily the receptor is sequestered into numerous discrete clusters that are associated with an uncoated pit membrane specialization called a caveola. By using two different methodological approaches, we found that the maintenance of both receptor clusters and caveolae depends upon the presence of cholesterol in the membrane. These results suggest that cholesterol plays a critical role in maintaining the caveola membrane domain and modulates the interaction of GPI-anchored membrane proteins via their phospholipid anchors.
TL;DR: An essential role for ω-3 fatty acids in retinal development is supported by electroretinogram results and the fatty acid composition of plasma and red blood cell (RBC) lipids were similar for all groups on entry but marked dietinduced differences were found after feeding the study diets.
Abstract: Effect of Dietary Omega-3 Fatty Acids on Retinal Function of Very-Low-Birth-Weight Neonates
TL;DR: The findings suggest that the signaling pathway activated by endotoxin is branched, and that selective inhibition of different parts of the pathway may be achieved through the use of distinct agents.
Abstract: The induction of cachectin/tumor necrosis factor (TNF) synthesis by bacterial endotoxins is a process that entails activation at several levels. Cachectin/TNF gene transcription is accelerated, leading to rapid accumulation of mRNA within the macrophage cytosol. In addition, translational derepression occurs, leading to far more efficient message utilization. Through the use of posttranscriptional reporter constructs, we now demonstrate that certain agents capable of inhibiting cachectin/TNF biosynthesis operate through different mechanisms. In RAW 264.7 macrophages, pentoxifylline blocks cachectin/TNF mRNA accumulation but has no effect upon the efficiency of reporter mRNA translation. Dexamethasone, on the other hand, has only a modest effect on cachectin/TNF mRNA accumulation, but strongly impedes translational derepression. Combined application of dexamethasone and pentoxifylline to macrophages causes a greater suppression of cachectin/TNF biosynthesis that can be achieved by either agent alone. These findings suggest that the signaling pathway activated by endotoxin is branched, and that selective inhibition of different parts of the pathway may be achieved through the use of distinct agents.
TL;DR: Both enzymes expressed in COS cells showed similar substrate specificities for naturally occurring steroid hormones, however, synthetic 4-azasteroids demonstrated marked differences in their abilities to inhibit the human and rat steroid 5 alpha-reductases.
Abstract: The microsomal enzyme steroid 5 alpha-reductase is responsible for the conversion of testosterone into the more potent androgen dihydrotestosterone. In man, this steroid acts on a variety of androgen-responsive target tissues to mediate such diverse endocrine processes as male sexual differentiation in the fetus and prostatic growth in men. Here we describe the isolation, structure, and expression of a cDNA encoding the human steroid 5 alpha-reductase. A rat cDNA was used as a hybridization probe to screen a human prostate cDNA library. A 2.1-kilobase cDNA was identified and DNA sequence analysis indicated that the human steroid 5 alpha-reductase was a hydrophobic protein of 259 amino acids with a predicted molecular weight of 29,462. A comparison of the human and rat protein sequences revealed a 60% identity. Transfection of expression vectors containing the human and rat cDNAs into simian COS cells resulted in the synthesis of high levels of steroid 5 alpha-reductase enzyme activity. Both enzymes expressed in COS cells showed similar substrate specificities for naturally occurring steroid hormones. However, synthetic 4-azasteroids demonstrated marked differences in their abilities to inhibit the human and rat steroid 5 alpha-reductases.
TL;DR: Using quantitative immunocytochemistry, it is shown that this receptor is highly clustered on the cell surface; these clusters are preferentially associated with uncoated membrane invaginations rather than clathrin-coated pits; and the receptor is not present in endosomes or lysosomes.
Abstract: The folate receptor, also known as the membrane folate-binding protein, is maximally expressed on the surface of folate-depleted tissue culture cells and mediates the high affinity accumulation of 5-methyltetrahydrofolic acid in the cytoplasm of these cells. Recent evidence suggests that this receptor recycles during folate internalization and that it is anchored in the membrane by a glycosyl-phosphatidylinositol linkage. Using quantitative immunocytochemistry, we now show that (a) this receptor is highly clustered on the cell surface; (b) these clusters are preferentially associated with uncoated membrane invaginations rather than clathrin-coated pits; and (c) the receptor is not present in endosomes or lysosomes. This receptor appears to physically move in and out of the cell using a novel uncoated pit pathway that does not merge with the clathrin-coated pit endocytic machinery.
TL;DR: The complete primary structure of the inositol 1,4,5-trisphosphate receptor from rat brain was elucidated using a series of overlapping cDNA clones, suggesting that it folded normally and that the amino-terminal sequences of the receptor are part of the ligand binding domain.
TL;DR: The low density lipoprotein receptor-related protein (LRP) from rat liver membranes binds apoprotein E (apoE)-enriched rabbit beta-migrating very lowdensity lipoproteins (beta-VLDL) in a ligand blotting assay on nitrocellulose membranes, raising the possibility that LRP functions as a receptor for apoE-enriched forms of these lipop Protein receptors in intact animals.
TL;DR: Results indicate that substantial amounts of ANG peptides are released into or generated within intrarenal fluid compartments, in which local ANG is likely to effect regulation of renal function independently of systemic ANG.
Abstract: To examine angiotensin (ANG) concentrations in fluid compartments near known intrarenal ANG receptors, we measured ANG concentrations in glomerular filtrate (GF), star vessel plasma (SVP), and luminal fluid from the early, mid, and late proximal tubule (E, M, and L PT). Samples were collected from euvolemic Munich-Wistar rats by free-flow micropuncture; ANG concentrations were measured by RIA. In one group of rats, concentrations of total immunoreactive ANG (reflecting ANG II and lesser amounts of three fragments) in GF and E, M, and L PT fluid averaged 29-40 nM compared with 32 pM in systemic plasma. In a second group, immunoreactive ANG concentrations in SVP also exceeded systemic levels by a factor of 1,000. In a final group, samples of GF and LPT fluid were purified by HPLC before RIA to measure ANG II and III concentrations specifically: their respective concentrations were 6-8 nM and 14-25 nM. We interpret these results to indicate that substantial amounts of ANG peptides are released into or generated within intrarenal fluid compartments, in which local ANG is likely to effect regulation of renal function independently of systemic ANG.
TL;DR: The results suggest that the weaker androgenic potency of testosterone compared to that of dihydrotestosterone resides in its weaker interaction with the androgen receptor, most clearly demonstrable as an increase in the dissociation rate of testosterone from the receptor.
Abstract: Testosterone and dihydrotestosterone are believed to exert their androgenic effects by interacting with a single intracellular receptor protein in androgen target tissues. During fetal life, however, testosterone mediates the virilization of the Wolffian ducts into the epididymis, vas deferens, and seminal vesicles, whereas the urogenital sinus and external genitalia require the in situ conversion of testosterone to dihydrotestosterone to undergo male development. The reason why the signal provided by testosterone needs to be amplified in some androgen target tissues but not in others remains an enigma. To provide insight into the different actions of these androgens we studied their interaction with the human androgen receptor in fibroblasts cultured from the genital skin of a patient with 5α-reductase deficiency. Dihydrotestosterone was formed in negligible amounts in these cells, and in some experiments the residual 5α-reductase activity was further blocked with the 5α-reductase inhibitor finasteride. ...
TL;DR: Cympathetic activity in patients with heart transplants or myasthenia gravis who were not being treated with cyclosporine was no different from that in Patients with essential hypertension or in normal controls, and cyclospora-induced hypertension is associated with sympathetic neural activation.
Abstract: Background. Hypertension is a frequent complication of cyclosporine-induced immunosuppression, but the underlying mechanism is unknown. In anesthetized animals, the administration of cyclosporine increases sympathetic-nerve discharge, which may contribute to hypertension. Methods. To determine whether cyclosporine-induced hypertension is accompanied by sustained sympathetic neural activation in patients, we recorded sympathetic action potentials using intraneural microelectrodes (in the peroneal nerve) in heart-transplant recipients receiving azathioprine and prednisone alone (n = 5) or in combination with cyclosporine (n = 14). We performed the same studies in eight patients with myasthenia gravis who were receiving cyclosporine and eight who were not, in five patients with essential hypertension, and in nine normal controls. Results. Heart-transplant recipients receiving cyclo-sporine had higher mean arterial blood pressure (±SE) than those not receiving cyclosporine (112±3 vs. 96±4 mm Hg; P<0....
Journal Article•
TL;DR: The results suggest that bile acids and sterols are able to alter the transcription of the 7 alpha-hydroxylase gene and that this control explains the previously observed feedback regulation of bile acid synthesis.
TL;DR: It is concluded that the presence of the HLA Class II antigen DQw1.2 is strongly protective against the development of IDDM, and that complete HLA-DQ typing is necessary for accurate assessment of susceptibility to IDDM.
Abstract: There is evidence that certain alleles at the HLA-DQ locus are correlated with susceptibility to insulin-dependent diabetes mellitus (IDDM) and in particular that DQ beta-chain alleles containing aspartic acid at position 57 are protective. The availability of a large group of patients with IDDM enabled us to assess the role of HLA-DQ alleles in susceptibility to the disease in order to confirm and extend recent observations derived from studies of smaller numbers of patients. Using allele-specific oligonucleotide probes and the polymerase chain reaction, we studied 266 unrelated patients with IDDM and 203 unrelated normal subjects for eight HLA-DQ beta-chain alleles. Two major findings emerged from these studies. First, the presence of an HLA-DQw1.2 allele was protective. Only 6 of the 266 patients with IDDM (2.3 percent) were positive for HLA-DQw1.2, as compared with 74 of the 203 normal subjects (36.4 percent; P less than 0.001). Thus, persons with the HLA-DQw1.2 allele, which is one of the polymorphic forms of the beta chain of the HLA-DQ molecule, rarely had IDDM, no matter which other HLA-DQ beta-chain allele they inherited ("dominant protection"). Second, the presence of the HLA-DQw8 allele increased the risk of IDDM. The relative risk of IDDM was 5.6 in persons homozygous for HLA-DQw8, and it was similar in persons with the HLA-DQw1.1/DQw8 or HLA-DQw2/DQw8 haplotype ("dominant susceptibility"). However, the relative risk of IDDM in persons who had the HLA-DQw1.2/DQw8 haplotype was 0.37, demonstrating that the protective effect of HLA-DQw1.2 predominated over the effect of HLA-DQw8. We conclude that the presence of the HLA Class II antigen DQw1.2 is strongly protective against the development of IDDM, and that complete HLA-DQ typing is necessary for accurate assessment of susceptibility to IDDM.
TL;DR: In this study the orthotropic elastic moduli, structural density, and fabric components were measured for 11 cancellous bone specimens from five bovine femora and for 75 specimens from three human proximal tibiae and fitted to these relationships using a least squares analysis.
TL;DR: Gel filtration experiments demonstrate a large conformational change of the receptor as a function of ligand binding, suggesting a mechanism by which ligandbinding might cause channel opening.
Abstract: The inositol-1,4,5-triphosphate (InsP3) receptor consists of a homotetramer of highly conserved 313 kd subunits that contain multiple transmembrane regions in the C-terminal part of the protein. The receptor was expressed in COS cells and its domain structure was studied by mutagenesis. Deletion of the transmembrane regions from the receptor results in the synthesis of a soluble receptor protein that efficiently binds InsP3 but which instead of associating into homotetramers remains monomeric. This result suggests a role for the transmembrane regions in the association of the receptor subunits into tetramers but not in ligand binding. To localize the ligand binding site, further cDNAs encoding truncated receptor proteins were constructed. Assays of InsP3 binding to these truncated InsP3 receptors revealed that sequences in the N-terminal fourth of the InsP3 receptor are sufficient for ligand binding. Accordingly, each subunit of the InsP3 receptor homotetramer contains an independent ligand binding site that is located on the N-terminal ends of each subunit and is separated from the putative channel-forming transmembrane regions by greater than 1400 amino acids. Gel filtration experiments demonstrate a large conformational change of the receptor as a function of ligand binding, suggesting a mechanism by which ligand binding might cause channel opening.
TL;DR: Analysis of t(1;14)(p32;q11) chromosome translocations from two patients with T cell acute lymphocytic leukemia has identified sequences within tal that potentially encode an amphipathic helix‐loop‐helix motif, a DNA‐binding domain found in a variety of proteins that control cell growth and differentiation.
Abstract: We have analyzed t(1;14)(p32;q11) chromosome translocations from two patients with T cell acute lymphocytic leukemia The chromosome 1 breakpoints of these patients lie within a kilobasepair of each other, and thus define a genetic locus (designated tal) involved in T cell oncogenesis Moreover, we have identified sequences within tal that potentially encode an amphipathic helix-loop-helix motif, a DNA-binding domain found in a variety of proteins that control cell growth and differentiation The homology domain of tal is especially related to that of lyl-1, a gene on chromosome 19 that has also been implicated in T cell oncogenesis Hence, tal and lyl-1 encode a distinct family of helix-loop-helix proteins involved in the malignant development of lymphocytes
TL;DR: MTF, a murine minor histocompatibility antigen, is maternally inherited and thought to be encoded by a mitochondrial gene, and cells can display peptides derived from mitochondrially encoded proteins, and such peptides can be histOCompatibility antigens.
TL;DR: T(1;14)(p32;q11) translocations and tald rearrangements disrupt the coding potential of tal‐1 in an equivalent manner, and thereby generate a common genetic lesion shared by a significant proportion of T‐ALL patients.
Abstract: The tal-1 gene is altered as a consequence of the t(1;14) (p32;q11) chromosome translocation observed in 3% of patients with T cell acute lymphoblastic leukemia (T-ALL). tal-1 encodes a helix-loop-helix (HLH) domain, a DNA binding and dimerization motif found in a number of proteins involved in cell growth and differentiation. We now report that an additional 25% of T-ALL patients bear tal-1 gene rearrangements that are not detected by karyotype analysis. These rearrangements result from a precise 90 kb deletion (designated tald) that arises independently in different patients by site-specific DNA recombination. Since the deletion junctions resemble the coding joints of assembled immunoglobulin genes, tald rearrangements are likely to be mediated by aberrant activity of the immunoglobulin recombinase. Moreover, t(1;14)(p32;q11) translocations and tald rearrangements disrupt the coding potential of tal-1 in an equivalent manner, and thereby generate a common genetic lesion shared by a significant proportion of T-ALL patients.
TL;DR: Article synthese sur le mecanisme permettant le transport des proteines secretees a partir du reticulum endoplasmique; interet porte au calcium and a son role dans ce transport biologique.
TL;DR: Measurements of outward Na+–Ca2+ exchange current in giant excised sarcolemmal Patches from guinea pig myocytes show a substantial decrease in exchange current during activation by cytoplasmic sodium, which seems to reflect an inactivation process rather than ion concentration changes or a 'first pass' exchange cycle.
Abstract: A plasmalemmal Na(+)-Ca2+ exchange mechanism is an important electrogenic determinant of contractility in cardiac cells. As in other cell types, calcium influx by Na(+)-Ca2+ exchange is secondarily activated by cytoplasmic calcium and probably ATP, but these modulatory mechanisms are either absent or altered in isolated cardiac sarcolemmal vesicles. Involvement of a calcium-dependent protein kinase in exchange regulation has been suggested but not verified. Here I describe measurements of outward Na(+)-Ca2+ exchange current, corresponding to calcium influx, in giant excised sarcolemmal patches from guinea pig myocytes. The exchange current is stimulated by both calcium and Mg-ATP from the cytoplasmic face, evidently through separate mechanisms. Activation by cytoplasmic calcium takes place within seconds, is reversible, and does not require ATP. Stimulation by Mg-ATP reverses only slowly over greater than 10 min, or not at all. Unexpectedly, a substantial decrease in exchange current occurs during activation by cytoplasmic sodium, which seems to reflect an inactivation process rather than ion concentration changes or a 'first pass' exchange cycle. This apparent inactivation, and the modulations by cytoplasmic calcium and Mg-ATP, are all abolished by brief treatment of the cytoplasmic surface with chymotrypsin, leaving the exchanger in a maintained state of high activity. Therefore, limited proteolysis deregulates Na(+)-Ca2+ exchange and could contribute to the loss of secondary regulation of the exchange in isolated sarcolemmal vesicles.