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Biomedical subjects

Paul Anderson

Publications and source records attributed to Paul Anderson.

At least 19 recordsLinked to original sources
PubMed2006

Tristetraprolin (TTP)-14-3-3 complex formation protects TTP from dephosphorylation by protein phosphatase 2a and stabilizes tumor necrosis factor-alpha mRNA.

Tumor necrosis factor (TNF)-alpha is a major cytokine produced by alveolar macrophages in response to pathogen-associated molecular patterns such as lipopolysaccharide. TNF-alpha secretion is regulated at both transcriptional and post-transcriptional levels. Post-transcriptional regulation occurs by modulation of TNF-alpha mRNA stability via the binding of tristetraprolin (TTP) to the adenosine/uridine-rich elements found in the 3'-untranslated region of the TNF-alpha transcript. Phosphorylation plays important roles in modulating mRNA stability, because activation of p38 MAPK by lipopolysaccharide stabilizes TNF-alpha mRNA. We hypothesized that the protein phosphatase 2A (PP2A) regulates this signaling pathway. Our results show that inhibition of PP2A by okadaic acid or small interference RNA significantly enhanced the stability of TNF-alpha mRNA. This result was associated with increased phosphorylation of p38 MAPK and MAPK-activated kinase 2 (MK-2). PP2A inhibition increased TTP phosphorylation and enhanced complex formation with chaperone protein 14-3-3. TTP physically interacted with PP2A in transfected mammalian cells. A functional consequence of TTP-14-3-3 complex formation appeared to be protection of TTP from dephosphorylation by inhibition of the binding of PP2A to phosphorylated TTP. Mutation of the MK-2 phosphorylation sites of TTP did not influence TNF-alpha adenosine/uridine-rich element binding and did not alter the increased TNF-alpha 3'-untranslated region-dependent luciferase activity induced by PP2A-small interference RNA silencing. Our data indicate that, although phosphorylation stabilizes TNF-alpha mRNA, PP2A regulates the mRNA stability by modulating the phosphorylation state of members of the p38/MK-2/TTP pathway.

14-3-3 Proteins↗
PubMed2006

Eukaryotic initiation factor 2alpha-independent pathway of stress granule induction by the natural product pateamine A.

Stress granules are aggregates of small ribosomal subunits, mRNA, and numerous associated RNA-binding proteins that include several translation initiation factors. Stress granule assembly occurs in the cytoplasm of higher eukaryotic cells under a wide variety of stress conditions, including heat shock, UV irradiation, hypoxia, and exposure to arsenite. Thus far, a unifying principle of eukaryotic initiation factor 2alpha phosphorylation prior to stress granule formation has been observed from the majority of experimental evidence. Pateamine A, a natural product isolated from marine sponge, was recently reported to inhibit eukaryotic translation initiation and induce the formation of stress granules. In this report, the protein composition and fundamental progression of stress granule formation and disassembly induced by pateamine A was found to be similar to that for arsenite. However, pateamine A-induced stress granules were more stable and less prone to disassembly than those formed in the presence of arsenite. Most significantly, pateamine A induced stress granules independent of eukaryotic initiation factor 2alpha phosphorylation, suggesting an alternative mechanism of formation from that previously described for other cellular stresses. Taking into account the known inhibitory effect of pateamine A on eukaryotic translation initiation, a model is proposed to account for the induction of stress granules by pateamine A as well as other stress conditions through perturbation of any steps prior to the rejoining of the 60S ribosomal subunit during the entire translation initiation process.

Animals↗
PubMed2006

RNA granules.

Cytoplasmic RNA granules in germ cells (polar and germinal granules), somatic cells (stress granules and processing bodies), and neurons (neuronal granules) have emerged as important players in the posttranscriptional regulation of gene expression. RNA granules contain various ribosomal subunits, translation factors, decay enzymes, helicases, scaffold proteins, and RNA-binding proteins, and they control the localization, stability, and translation of their RNA cargo. We review the relationship between different classes of these granules and discuss how spatial organization regulates messenger RNA translation/decay.

Animals↗
PubMed2006

Neurologic deterioration secondary to unrecognized spinal instability following trauma--a multicenter study.

STUDY DESIGN: A retrospective study was undertaken that evaluated the medical records and imaging studies of a subset of patients with spinal injury from large level I trauma centers. OBJECTIVE: To characterize patients with spinal injuries who had neurologic deterioration due to unrecognized instability. SUMMARY OF BACKGROUND DATA: Controversy exists regarding the most appropriate imaging studies required to "clear" the spine in patients suspected of having a spinal column injury. Although most bony and/or ligamentous spine injuries are detected early, an occasional patient has an occult injury, which is not detected, and a potentially straightforward problem becomes a neurologic catastrophe. METHODS: The study was designed as a retrospective review of patients who had neurologic deterioration as a direct result of an unrecognized fracture, subluxation, or soft tissue injury of the cervical, thoracic, or lumbar spine from 8 level I trauma centers. Demographics, injury information, and neurologic outcome were collected. The etiology and incidence of the missed injury were determined. RESULTS: A total of 24 patients were identified who were treated or referred to 1 of the participating trauma centers and had an adverse neurologic outcome as a result of the missed injury. The average age of the patients was 50 years (range 18-92), and average delay in diagnosis was 19.8 days. Radiculopathy developed in 5 patients, 16 had spinal cord injuries, and 3 patients died as a result of their neurologic injury. The most common reason for the missed injury was insufficient imaging studies (58.3%), while only 33.3% were a result of misread radiographs or 8.3% poor quality radiographs. The incidence of missed injuries resulting in neurologic injury in patients with spine fractures or strains was 0.21%, and the incidence as a percentage of all trauma patients evaluated was 0.025%. CONCLUSIONS: This multicenter study establishes that missed spinal injuries resulting in a neurologic deficit continue to occur in major trauma centers despite the presence of experienced personnel and sophisticated imaging techniques. Older age, high impact accidents, and patients with insufficient imaging are at highest risk.

Adolescent↗
PubMed2006

Characterization of peripheral natural killer cells in primary Sjögren's syndrome: impaired NK cell activity and low NK cell number.

The aim of this study was to compare the number of peripheral blood natural killer (NK) cells, NK cell activity, expression of NK cell activating receptors, and serum cytokine levels in patients with primary Sjögren's syndrome (SS) vs normal controls. The authors found that NK cell number, NK cell killing activity, and the expression of activating receptors CD2 and NKG2D were significantly decreased, and the expression of NKp46, as well as the percentage of apoptotic NK cells, were significantly increased in primary SS patients compared with healthy controls. NK cell killing activity on a per-cell basis was similar in primary SS patients and healthy controls. Moreover, the levels of IL-18 and TNF-alpha, cytokines that have been shown to promote NK cell death, were significantly increased in sera from patients with primary SS compared with controls. These data suggest that reduced NK cell numbers, probably a result of apoptotic death, may contribute to impaired NK cell activity in patients with primary SS.

Apoptosis↗
PubMed2006

Posttranscriptional mechanisms regulating the inflammatory response.

The inflammatory response is a complex physiologic process that requires the coordinate induction of cytokines, chemokines, angiogenic factors, effector-enzymes, and proteases. Although transcriptional activation is required to turn on the inflammatory response, recent studies have revealed that posttranscriptional mechanisms play an important role by determining the rate at which mRNAs encoding inflammatory effector proteins are translated and degraded. Most posttranscriptional control mechanisms function to dampen the expression of pro-inflammatory proteins to ensure that potentially injurious proteins are not overexpressed during an inflammatory response. Here we discuss the factors that regulate the stability and translation of mRNAs encoding pro-inflammatory proteins.

Animals↗
PubMed2006

ARE-mRNA degradation requires the 5'-3' decay pathway.

As an important mode of suppressing gene expression, messenger RNAs containing an AU-rich element (ARE) in the 3' untranslated region are rapidly degraded in the cytoplasm. ARE-mediated mRNA decay (AMD) is initiated by deadenylation, and in vitro studies have indicated that subsequent degradation occurs in the 3'-5' direction through a complex of exonucleases termed the exosome. An alternative pathway of mRNA degradation occurs at processing bodies, cytoplasmic foci that contain decapping enzymes, the 5'-3' exonuclease Xrn1 and the Lsm1-7 heptamer. To determine which of the two pathways is important for AMD in live cells, we targeted components of both pathways using short interfering RNA in human HT1080 cells. We show that Xrn1 and Lsm1 are essential for AMD. On the other side, out of three exosome components tested, only knockdown of PmScl-75 caused a strong inhibition of AMD. Our results show that mammalian cells, similar to yeast, require the 5'-3' Xrn1 pathway to degrade ARE-mRNAs.

3' Untranslated Regions↗
PubMed2006

KTP laser versus transurethral resection: early results of a randomized trial.

BACKGROUND AND PURPOSE: Many technologies have been mooted as equal to transurethral resection of the prostate (TURP) without gaining widespread acceptance because of the lack of randomized trials. The Greenlight laser system (Laserscope, San Jose, Ca.), an 80 W system for photovaporization of the prostate (PVP), was compared with TURP in such a trial. PATIENTS AND METHODS: A series of 120 patients was randomized to undergo TURP or PVP after evaluation, which was repeated at 1, 3, 6, and 12 months after treatment. Irrigation use, length of catherization (LOC), length of hospital stay (LOS), postvoiding residual volume, sexual function, blood loss, cost, and operative time also were assessed. RESULTS: To date, 76 patients are evaluable. Both groups showed a significant (P < 0.5) increase in maximum flow rate from baseline. In the TURP group, flow increased from 8.7 to 17.9 mL/sec (149%) and in the PVP group from 8.5 to 20.6 mL/sec (167%). The International Prostate Symptom Score decreased from 25.4 to 12.4(50.23%) in the TURP group and from 25.7 to 12.0 (49.83%) in the PVP group. Postvoiding residual volumes also showed significant decreases. Similar trends were seen in relation to bother and quality of life scores. There was no difference in sexual function as measured by a questionnaire. The LOC was significantly less in the PVP group (P < 0.001), the mean being 12.2 hours (range 0-24 hours) versus 44.5 hours for TURP (range 6-192 hours). A similar situation was seen in relation to LOS (P < 0.0001), with the mean of the PVP group being 1.08 days (range 1-2 days) and the mean for the TURP group being 3.4 days (range 3-9 days). Adverse events were less frequent in the PVP group, and the costs were 22% less. CONCLUSIONS: This trial demonstrates that PVP is effective compared with TURP, producing equivalent improvements in flow rates and IPSS with markedly reduced LOS, LOC, and adverse events. Long-term follow- up is being undertaken to assess the durability of these results.

Aged↗
PubMed2005

Non-destructive studies of tissue-engineered phalanges by magnetic resonance microscopy and X-ray microtomography.

One of the intents of tissue engineering is to fabricate biological materials for the augmentation or replacement of impaired, damaged, or diseased human tissue. In this context, novel models of the human phalanges have been developed recently through suturing of polymer scaffolds supporting osteoblasts, chondrocytes, and tenocytes to mimic bone, cartilage, and tendon, respectively. Characterization of the model constructs has been accomplished previously through histological and biochemical means, both of which are necessarily destructive to the constructs. This report describes the application of two complementary, non-destructive, non-invasive techniques, magnetic resonance microscopy (MRM) and X-ray microtomography (XMT or quantitative computed tomography), to evaluate the spatial and temporal growth and developmental status of tissue elements within tissue-engineered constructs obtained after 10 and 38 weeks of implantation in athymic (nude) mice. These two times represent respective points at which model middle phalanges are comprised principally of organic components while being largely unmineralized and later become increasingly more mineralized. The spatial distribution of mineralized deposits within intact constructs was readily detected by XMT (qCT) and was comparable to low intensity zones observed on MRM hydration maps. Moreover, the MRM-derived hydration values for mineralized zones were inversely correlated with mineral densities measured by XMT. In addition, the MRM method successfully mapped fat deposits, collagenous tissues, and the hydration state of the soft tissue elements comprising the specimens. These results support the application of non-destructive, non-invasive, quantitative MRM and XMT for the evaluation of constituent tissue elements within complex constructs of engineered implants.

Animals↗
PubMed2005

HuR as a negative posttranscriptional modulator in inflammation.

HuR is an RNA binding protein with an alleged role in the posttranscriptional activation of inflammatory mRNAs bearing AU-rich elements (AREs). Here, we show that the inducible increase of HuR in murine innate compartments suppresses inflammatory responses in vivo. In macrophages, HuR overexpression induced the translational silencing of specific cytokine mRNAs despite positive or nominal effects on their corresponding turnover. By using a model system of ARE dysfunction, we demonstrate that HuR does not alter the accumulation of target mRNAs in the absence of the destabilizing functions of Tristetraprolin but synergizes with the translational silencer TIA-1 to reduce the translation of cytokine mRNAs. Our data suggest that HuR acts in a pleiotropic fashion in inflammation through its functional interactions with specific mRNA subsets and negative posttranscriptional modules.

Animals↗
PubMed2005

Stress granules and processing bodies are dynamically linked sites of mRNP remodeling.

Stress granules (SGs) are cytoplasmic aggregates of stalled translational preinitiation complexes that accumulate during stress. GW bodies/processing bodies (PBs) are distinct cytoplasmic sites of mRNA degradation. In this study, we show that SGs and PBs are spatially, compositionally, and functionally linked. SGs and PBs are induced by stress, but SG assembly requires eIF2alpha phosphorylation, whereas PB assembly does not. They are also dispersed by inhibitors of translational elongation and share several protein components, including Fas-activated serine/threonine phosphoprotein, XRN1, eIF4E, and tristetraprolin (TTP). In contrast, eIF3, G3BP, eIF4G, and PABP-1 are restricted to SGs, whereas DCP1a and 2 are confined to PBs. SGs and PBs also can harbor the same species of mRNA and physically associate with one another in vivo, an interaction that is promoted by the related mRNA decay factors TTP and BRF1. We propose that mRNA released from disassembled polysomes is sorted and remodeled at SGs, from which selected transcripts are delivered to PBs for degradation.

Animals↗
PubMed2005

Importance of eIF2alpha phosphorylation and stress granule assembly in alphavirus translation regulation.

Alphavirus infection results in the shutoff of host protein synthesis in favor of viral translation. Here, we show that during Semliki Forest virus (SFV) infection, the translation inhibition is largely due to the activation of the cellular stress response via phosphorylation of eukaryotic translation initiation factor 2alpha subunit (eIF2alpha). Infection of mouse embryo fibroblasts (MEFs) expressing a nonphosphorylatable mutant of eIF2alpha does not result in efficient shutoff, despite efficient viral protein production. Furthermore, we show that the SFV translation enhancer element counteracts the translation inhibition imposed by eIF2alpha phosphorylation. In wild-type MEFs, viral infection induces the transient formation of stress granules (SGs) containing the cellular TIA-1/R proteins. These SGs are disassembled in the vicinity of viral RNA replication, synchronously with the switch from cellular to viral gene expression. We propose that phosphorylation of eIF2alpha and the consequent SG assembly is important for shutoff to occur and that the localized SG disassembly and the presence of the enhancer aid the SFV mRNAs to elude general translational arrest.

Alphavirus↗
PubMed2005

Heme-regulated inhibitor kinase-mediated phosphorylation of eukaryotic translation initiation factor 2 inhibits translation, induces stress granule formation, and mediates survival upon arsenite exposure.

Exposure to arsenite inhibits protein synthesis and activates multiple stress signaling pathways. Although arsenite has diverse effects on cell metabolism, we demonstrated that phosphorylation of eukaryotic translation initiation factor 2 at Ser-51 on the alpha subunit was necessary to inhibit protein synthesis initiation in arsenite-treated cells and was essential for stress granule formation. Of the four protein kinases known to phosphorylate eukaryotic translation initiation factor 2alpha, only the heme-regulated inhibitor kinase (HRI) was required for the translational inhibition in response to arsenite treatment in mouse embryonic fibroblasts. In addition, HRI expression was required for stress granule formation and cellular survival after arsenite treatment. In vivo studies elucidated a fundamental requirement for HRI in murine survival upon acute arsenite exposure. The results demonstrated an essential role for HRI in mediating arsenite stress-induced phosphorylation of eukaryotic translation initiation factor 2alpha, inhibition of protein synthesis, stress granule formation, and survival.

Animals↗
PubMed2005

Granzyme B and natural killer (NK) cell death.

Granzyme B is a unique serine protease, which plays a crucial role for target cell death. Several mechanisms of delivery of granzyme B to target cells have been recently identified. Granzyme B directly activates Bid, a specific substrate for granzyme B, resulting in caspase activation. Granzyme B efficiently cleaves many prominent autoantigens, and the hypothesis that autoantibodies arise when cryptic determinants are revealed to the immune system has been proposed. Some autoantibodies directed against granzyme B-specific neoepitopes are present in serum from patients with autoimmune diseases. In the tissues from autoimmune diseases, granzyme B might play an important role for disease progression (i.e., rheumatoid arthritis synovium) or inhibition (i.e., regulatory T cells). We have identified a novel type of activation-induced cell death (granzyme B leakage-induced cell death). Activation-induced natural killer (NK) cell death is accompanied by the leakage of granzyme B from intracellular granules into the cytoplasm, and it triggers apoptosis by directing Bid to mitochondrial membranes. An excess of "leaked" granzyme B over its inhibitor, serpin proteinase inhibitor 9, is a major determinant of cell death. The role of granzyme B in autoimmunity and its influence on NK cell death are discussed.

Journal Article↗
PubMed2005

A Place for RNAi.

Processing bodies (P bodies) are discrete cytoplasmic foci to which mRNA is routed for degradation. In mammalian cells, they are also associated with miRNA-induced translational silencing and siRNA-induced mRNA degradation. In a recent issue of Molecular Cell, Ding and coworkers described an argonaute-interacting protein that appears to promote the assembly of P bodies in C. elegans (Ding et al., 2005).

Animals↗