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Biomedical subjects

B M Sullivan

Publications and source records attributed to B M Sullivan.

16 recordsLinked to original sources
PubMed2002

The transcription factor T-bet regulates mucosal T cell activation in experimental colitis and Crohn's disease.

The balance between pro and antiinflammatory cytokines secreted by T cells regulates both the initiation and perpetuation of inflammatory bowel diseases (IBD). In particular, the balance between interferon (IFN)-gamma/interleukin (IL)-4 and transforming growth factor (TGF)-beta activity controls chronic intestinal inflammation. However, the molecular pathways that evoke these responses are not well understood. Here, we describe a critical role for the transcription factor T-bet in controlling the mucosal cytokine balance and clinical disease. We studied the expression and function of T-bet in patients with IBD and in mucosal T cells in various T helper (Th)1- and Th2-mediated animal models of chronic intestinal inflammation by taking advantage of mice that lack T-bet and retroviral transduction techniques, respectively. Whereas retroviral transduction of T-bet in CD62L(+) CD4(+) T cells exacerbated colitis in reconstituted SCID mice, T-bet-deficient T cells failed to induce colitis in adoptive transfer experiments suggesting that overexpression of T-bet is essential and sufficient to promote Th1-mediated colitis in vivo. Furthermore, T-bet-deficient CD62L(-) CD4(+) T cells showed enhanced protective functions in Th1-mediated colitis and exhibited increased TGF-beta signaling suggesting that a T-bet driven pathway of T cell activation controls the intestinal balance between IFN-gamma/IL-4 and TGF-beta responses and the development of chronic intestinal inflammation in T cell-mediated colitis. Furthermore, TGF-beta was found to suppress T-bet expression suggesting a reciprocal relationship between TGF-beta and T-bet in mucosal T cells. In summary, our data suggest a key regulatory role of T-bet in the pathogenesis of T cell-mediated colitis. Specific targeting of this pathway may be a promising novel approach for the treatment of patients with Crohn's disease and other autoimmune diseases mediated by Th1 T lymphocytes.

Adult↗
PubMed2001

Polycystin-1 interacts with intermediate filaments.

Polycystin-1, the protein defective in a majority of patients with autosomal dominant polycystic kidney disease, is a ubiquitously expressed multi-span transmembrane protein of unknown function. Subcellular localization studies found this protein to be a component of various cell junctional complexes and to be associated with the cytoskeleton, but the specificity and nature of such associations are not known. To identify proteins that interact with the polycystin-1 C-tail (P1CT), this segment was used as bait in a yeast two-hybrid screening of a kidney epithelial cell library. The intermediate filament (IF) protein vimentin was identified as a strong polycystin-1-interacting partner. Cytokeratins K8 and K18 and desmin were also found to interact with P1CT. These interactions were mediated by coiled-coil motifs in polycystin-1 and IF proteins. Vimentin, cytokeratins K8 and K18, and desmin also bound directly to P1CT in GST pull-down and in in vitro filament assembly assays. Two observations confirmed these interactions in vivo: (i) a cell membrane-anchored form of recombinant P1CT decorated the IF network and was found to associate with the cytoskeleton in detergent-solubilized cells and (ii) endogenous polycystin-1 distributed with IF at desmosomal junctions. Polycystin-1 may utilize this association for structural, storage, or signaling functions.

Amino Acid Sequence↗
PubMed2001

The V protein of human parainfluenza virus 2 antagonizes type I interferon responses by destabilizing signal transducer and activator of transcription 2.

Type I interferon (IFN) induces antiviral responses through the activation of the ISGF3 transcription factor complex that contains the subunit proteins STAT1, STAT2, and p48/ISGF3 gamma/IRF9. The ability of some human paramyxoviruses to overcome IFN actions by specific proteolysis of STAT proteins has been examined. Infection of cells with type 2, but not type 1 or type 3 human parainfluenza virus (HPIV) leads to a loss of cellular STAT2 protein. Expression of a single HPIV2 protein derived from the V open reading frame blocks IFN-dependent transcriptional responses in the absence of other viral proteins. The loss of IFN response is due to V-protein-induced proteolytic degradation of STAT2. Expression of HPIV2 V causes the normally stable STAT2 protein to be rapidly degraded, and this proteolytic activity can be partially alleviated by proteasome inhibition. No V-protein-specific effects on STAT2 mRNA levels were observed. The results indicate that the V protein of HPIV2 is sufficient to recognize and target a specific cellular transcription factor for destruction by cellular machinery.

Cell Line↗
PubMed2000

RGS4 and RGS2 bind coatomer and inhibit COPI association with Golgi membranes and intracellular transport.

COPI, a protein complex consisting of coatomer and the small GTPase ARF1, is an integral component of some intracellular transport carriers. The association of COPI with secretory membranes has been implicated in the maintenance of Golgi integrity and the normal functioning of intracellular transport in eukaryotes. The regulator of G protein signaling, RGS4, interacted with the COPI subunit beta'-COP in a yeast two-hybrid screen. Both recombinant RGS4 and RGS2 bound purified recombinant beta'-COP in vitro. Endogenous cytosolic RGS4 from NG108 cells and RGS2 from HEK293T cells cofractionated with the COPI complex by gel filtration. Binding of beta'-COP to RGS4 occurred through two dilysine motifs in RGS4, similar to those contained in some aminoglycoside antibiotics that are known to bind coatomer. RGS4 inhibited COPI binding to Golgi membranes independently of its GTPase-accelerating activity on G(ialpha). In RGS4-transfected LLC-PK1 cells, the amount of COPI in the Golgi region was considerably reduced compared with that in wild-type cells, but there was no detectable difference in the amount of either Golgi-associated ARF1 or the integral Golgi membrane protein giantin, indicating that Golgi integrity was preserved. In addition, RGS4 expression inhibited trafficking of aquaporin 1 to the plasma membrane in LLC-PK1 cells and impaired secretion of placental alkaline phosphatase from HEK293T cells. The inhibitory effect of RGS4 in these assays was independent of GTPase-accelerating activity but correlated with its ability to bind COPI. Thus, these data support the hypothesis that these RGS proteins sequester coatomer in the cytoplasm and inhibit its recruitment onto Golgi membranes, which may in turn modulate Golgi-plasma membrane or intra-Golgi transport.

Alkaline Phosphatase↗
PubMed1998

Expression of GTPase-deficient Gialpha2 results in translocation of cytoplasmic RGS4 to the plasma membrane.

The members of a recently identified protein family termed regulators of G-protein signaling (RGS) act as GTPase-activating proteins for certain Galpha subunits in vitro, but their physiological effects in cells are uncertain in the face of similar biochemical activity and overlapping patterns of tissue expression. Consistent with its activity in in vitro GTPase-activating protein assays, RGS4 interacts efficiently with endogenous proteins of the Gi and Gq subclasses of Galpha subunits but not with G12alpha or Gsalpha. Unlike other RGS proteins such as RGS9, RGS-GAIP, and Sst2p, which have been reported to be largely membrane-associated, a majority of cellular RGS4 is found as a soluble protein in the cytoplasm. However, the expression of a GTPase-deficient Gialpha subunit (Gialpha2-Q204L) resulted in the translocation of both wild type RGS4 and a non-Gialpha-binding mutant (L159F) to the plasma membrane. These data suggest that RGS4 may be recruited to the plasma membrane indirectly by G-protein activation and that multiple RGS proteins within a given cell might be differentially localized to determine a physiologic response to a G-protein-linked stimulus.

Animals↗
PubMed1997

Localization of human heparan glucosaminyl N-deacetylase/N-sulphotransferase to the trans-Golgi network.

In order to determine the intracellular location of heparan N-deacetylase/N-sulphotransferase, cDNAs encoding human heparan glucosaminyl N-deacetylase/N-sulphotransferase were cloned from human umbilical vein endothelial cells. The deduced amino acid sequence was identical to that of the human heparan N-sulphotransferase cloned previously [Dixon, Loftus, Gladwin, Scambler, Wasmuth and Dixon (1995) Genomics 26, 239-244]. RNA blot analysis indicated that two heparan N-sulphotransferase transcripts of approx. 8.5 and 4 kb were produced in all tissues. Expression was most abundant in heart, liver and pancreas. A cDNA encoding a Flag-tagged human heparan N-sulphotransferase (where Flag is an epitope with the sequence DYKDDDDK) was transfected into mouse LTA cells. Immunofluorescence detection using anti-Flag monoclonal antibodies demonstrated that the enzyme was localized to the trans-Golgi network. A truncated Flag-tagged heparan N-sulphotransferase was also retained in the Golgi, indicating that, as for many other Golgi enzymes, the N-terminal region of heparan N-sulphotransferase is sufficient for retention in the Golgi apparatus.

Amidohydrolases↗
PubMed1996

A role for endothelial NO synthase in LTP revealed by adenovirus-mediated inhibition and rescue.

Pharmacological studies support the idea that nitric oxide (NO) serves as a retrograde messenger during long-term potentiation (LTP) in area CA1 of the hippocampus. Mice with a defective form of the gene for neuronal NO synthase (nNOS), however, exhibit normal LTP. The myristoyl protein endothelial NOS (eNOS) is present in the dendrites of CA1 neurons. Recombinant adenovirus vectors containing either a truncated eNOS (a putative dominant negative) or an eNOS fused to a transmembrane protein were used to demonstrate that membrane-targeted eNOS is required for LTP. The membrane localization of eNOS may optimally position the enzyme both to respond to Ca2+ influx and to release NO into the extracellular space during LTP induction.

Adenoviridae↗
PubMed1996

Detection of immobilized amplicons by ELISA-like techniques.

The NucleoLink surface is a physically modified, thermostable, optically clear resin. It allows the covalent binding of 5'-phosphorylated oligonucleotides. Target DNA amplification by polymerase chain reaction (PCR) is accomplished by asymmetric amplification on the covalently immobilized primer that develops into immobilized amplicons. A DNA fragment of bovine leukemia virus is used as a model system for the detection of immobilized amplicons by ELISA-like techniques. Covalently bound oligonucleotides are also utilized as capture probe in the hybridization-based signal amplification for detection of an infectious organism.

DNA, Viral↗
PubMed1990

A comparison of overall health between patients with rheumatoid arthritis and a population with and without rheumatoid arthritis.

Women with rheumatoid arthritis (RA) at a rheumatology outpatient clinic (PAT) were compared with women with RA in representative samples of the Gothenburg population (POP), and with non-arthritic women in this population (REF). Clinical routine measures disclosed substantial dysfunction in both RA groups. Their physical, psychosocial, and overall function, assessed by means of the Sickness Impact Profile (SIP), was more impaired than that of the REF. The PAT had a higher disease activity and worse overall health status than the POP. In definite and classical RA, a poorer SIP physical and overall function was noted in the PAT than in the POP group, despite similar mean age and mean disease duration. Women with probable RA in the POP group had worse SIP dysfunction than the REF, particularly regarding ambulation and personal care. The SIP was sensitive to variations in disease activity and comprehensively disclosed dysfunction better than routine clinical measures.

Activities of Daily Living↗
PubMed1985

Emphysema in the renal allograft.

Two diabetic patients in whom emphysematous pyelonephritis developed after renal transplantation are described. Clinical recognition of this unusual and serious infection is masked by the effects of immunosuppression. Abdominal radiographic, ultrasound, and computed tomography findings are discussed. The clinical presentation includes urinary tract infection, sepsis, and acute tubular malfunction of the allograft in insulin-dependent diabetics.

Adult↗
PubMed1984

CT appearance of multifocal hepatic steatosis.

The CT appearance of focal and diffuse fatty infiltration of the liver has been described in recent radiologic literature. Previous reports of focal steatosis have emphasized the differential diagnosis of the solitary lesion. We report a case of multifocal hepatic involvement and describe a new radiologic sign that is useful in differentiating this process from neoplasia.

Aged↗
PubMedDate not supplied

Modification of hippocampal synaptic proteins by nitric oxide-stimulated ADP ribosylation.

Nitric oxide has been shown to be an important neuronal signaling molecule that participates in both behavioral and synaptic plasticity. To better understand the potential mechanisms by which NO regulates synaptic function, the ability of NO to stimulate the modification of synaptic proteins by ADP ribosylation was examined. Two NO donors, sodium nitroprusside and 3-morpholinosydnonimine, stimulated the ADP ribosylation of proteins at apparent molecular masses of 42, 48, 51, 54, and 74 kD in hippocampal synaptosomes. This stimulation was likely owing to the production of NO by the donors; ADP ribosylation was not stimulated by non-NO decomposition products of sodium nitroprusside, and quenching of superoxide anion did not inhibit Sin-1-induced ADP ribosylation. Experiments using NAD+ that was radiolabeled on the nicotinamide moiety demonstrated that the modification of proteins of molecular masses of 30, 33, and 38 kD are not true ADP ribosylation, whereas labeling of the 42-, 48-, 51-, 54-, and 74-kD proteins likely represent ADP ribosylation. Some of the substrates were brain specific (54 and 74 kD), whereas others (42 and 51 kD) were present in multiple nonbrain tissues.

Adenosine Diphosphate Ribose↗
PubMedDate not supplied

The accuracy of tuberculin skin tests: self-assessment by adult outpatients.

Tuberculin skin testing is an accurate, inexpensive screening procedure for detecting tuberculosis infection. The return visit needed to interpret the reaction is inconvenient, costly, and may contribute to under-utilization of the test. Although some clinicians ask patients to read their own purified protein derivative (PPD) test results, patient accuracy and the degree of teaching needed to learn this skill are unclear. This study evaluated the accuracy with which 145 outpatients read their own Mantoux skin test (PPD) reactions and reported by postcard after brief training by nurse practitioners. A total of 89 instructed patients returned postcards and also returned for clinician readings; 46 submitted postcards without returning; 7 returned but did not complete postcards; and 3 neither returned postcards nor returned for readings. Ten of 135 postcards were uninterpretable. For 81 subjects with both interpretable tuberculin self-assessment postcards and clinician readings, overall PPD classification agreement was 88 percent; Kappaw = +0.905 (P less than .001). Compared to clinician readings, 1 of 53 patients falsely reported a positive reaction (greater than or equal to 10 mm) and 2 of 25 patients falsely reported negative PPD readings (0-4 mm). There was 100 percent agreement between postcard readings and clinician classifications in a subgroup of patients (N = 26), prospectively identified by nurse practitioners as capable of accurate tuberculin self-assessment. Inter-clinician reading agreement (N = 37) was 89 percent; Kappaw = +0.943 (P less than .001). The brief standardized teaching protocol described can enable most patients to measure and report their PPD results. Study results suggest thatpostcard reports, especially negative ones, from a subgroup of patients selected for their skill in measuring their initial PPD wheal and ability to paraphrase instructions, might be substituted for clinician readings.

Ambulatory Care↗