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Morris DP, Snipes LC, Hill SA, Woods MM, Mbugua MM, Wade LR, McMurry JL. Corrigendum: A reversible cell penetrating peptide-cargo linkage allows dissection of cell penetrating peptide-and cargo- dependent effects on internalization and identifies new functionalities of putative endolytic peptides. Front Pharmacol 2023; 14:1152506. [PMID: 37144219 PMCID: PMC10152549 DOI: 10.3389/fphar.2023.1152506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Accepted: 03/30/2023] [Indexed: 05/06/2023] Open
Abstract
[This corrects the article DOI: 10.3389/fphar.2022.1070464.].
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Morris DP, Snipes LC, Hill SA, Woods MM, Mbugua MM, Wade LR, McMurry JL. A reversible cell penetrating peptide-cargo linkage allows dissection of cell penetrating peptide- and cargo-dependent effects on internalization and identifies new functionalities of putative endolytic peptides. Front Pharmacol 2022; 13:1070464. [PMID: 36479201 PMCID: PMC9720253 DOI: 10.3389/fphar.2022.1070464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 11/09/2022] [Indexed: 11/23/2022] Open
Abstract
Cell penetrating peptides (CPPs) are a promising technology for therapeutic delivery of macromolecular cargos. CPPs have generally used covalent linkages to cargo, ensuring a common fate as one molecule. Conversely, our CPP-adaptor, TAT-CaM, noncovalently binds calmodulin binding sequence (CBS)-containing cargos in calcium rich media then dissociates in the calcium-poor endosomal environment following internalization, enhancing endosomal escape relative to standard CPPs. In this study, we report cell entry of positively charged protein cargos that were not increased by TAT-CaM while cargos based on the negatively charged maltose binding protein (MBP) displayed little intrinsic internalization but were internalized by TAT-CaM. In addition, association of positively charged proteins with negatively charged nucleic acids reduced internalization. This evidence points to the dominant role cargo charge plays in apparent CPP effectiveness. There has been little systematic investigation as to how interaction between CPPs and cargos impacts internalization efficiency. Our adaptors provide a tool that allows combinatorial assays to detect emergent properties. Toward this end we added 4 endolytic peptide (EP) sequences between cargo CBS and MBP moieties to create 4 new cargos and between TAT and CaM to create 4 new adaptors. The new cargos were assayed for internalization alone and with a panel of CPP-adaptors to identify combinations that displayed increased internalization efficiency or other properties. Among the most important results, addition of the EP LAH4 improved adaptor performance and provided some CPP capability to cargos. MBP-LAH4-CBS was internalized more effectively by most adaptors, suggesting this sequence has general stimulatory ability. Two other EPs, Aurein 1.2 and HA2, also provided some CPP capability to their MBP cargos but were unexpectedly antagonistic to internalization by most adaptors due to retention of adaptor/cargo complexes on the cell surface. We thus identified LAH4 as stimulator of internalization in both adaptors and cargos and uncovered new functionality for Aurein 1.2 and HA2, which may be related to their identification as EPs. Future experiments will test new endolytic capabilities made possible with combinatorial approaches.
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Sepulveda DE, Morris DP, Raup-Konsavage WM, Sun D, Vrana KE, Graziane NM. Evaluating the Antinociceptive Efficacy of Cannabidiol Alone or in Combination with Morphine Using the Formalin Test in Male and Female Mice. Cannabis Cannabinoid Res 2022; 7:648-657. [PMID: 34846928 PMCID: PMC9587782 DOI: 10.1089/can.2021.0108] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Introduction: Phytocannabinoids have emerged as a potential alternative treatment option for individuals experiencing persistent pain. However, evidence-based research regarding their clinical utility in both males and females remains incomplete. In addition, it is unknown whether combining readily available cannabinoids with opioids has a synergistic or subadditive effect on pain modulation. To begin to fill this knowledge gap, we investigated the antinociceptive effects of the phytocannabinoid, CBD, either alone or in combination with opioids in male and female C57BL/6J mice. Results: Using the formalin test, our results show that CBD (10 mg/kg, i.p.) treatment evoked antinociception in phase I, but not in phase II, of the formalin test in male mice. However, in female mice, CBD showed no significant antinociceptive effect. In addition, a direct sex comparison showed that CBD evoked a significant increase in nociceptive behaviors in female versus male mice during phase I of the formalin test. Furthermore, we show that CBD (10 mg/kg, i.p.) in combination with low-dose morphine (1 mg/kg, i.p.) was ineffective at eliciting a synergistic antinociceptive response in both male and female mice. Lastly, consistent with previous literature, we showed that females treated with a relatively higher dose of morphine (10 mg/kg, i.p.) displayed a significant increase in the variability of nociceptive behaviors compared to morphine-treated male mice. Conclusion: Overall, our results suggest that CBD treatment may have beneficial antinociceptive effects during the acute phase of persistent pain, but these effects are more beneficial to males than females. We provide further pre-clinical support that treatments geared toward reducing nociceptive behaviors differentially affect males and females.
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Affiliation(s)
- Diana E. Sepulveda
- Department of Pharmacology, Penn State University College of Medicine, Hershey, Pennsylvania, USA
- Department of Department of Anesthesiology and Perioperative Medicine, Penn State University College of Medicine, Hershey, Pennsylvania, USA
| | | | - Wesley M. Raup-Konsavage
- Department of Pharmacology, Penn State University College of Medicine, Hershey, Pennsylvania, USA
| | - Dongxiao Sun
- Department of Pharmacology, Penn State University College of Medicine, Hershey, Pennsylvania, USA
| | - Kent E. Vrana
- Department of Pharmacology, Penn State University College of Medicine, Hershey, Pennsylvania, USA
| | - Nicholas M. Graziane
- Department of Pharmacology, Penn State University College of Medicine, Hershey, Pennsylvania, USA
- Department of Department of Anesthesiology and Perioperative Medicine, Penn State University College of Medicine, Hershey, Pennsylvania, USA
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Sepulveda DE, Morris DP, Raup-Konsavage WM, Sun D, Vrana KE, Graziane NM. Cannabigerol (CBG) attenuates mechanical hypersensitivity elicited by chemotherapy-induced peripheral neuropathy. Eur J Pain 2022; 26:1950-1966. [PMID: 35899583 DOI: 10.1002/ejp.2016] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 07/18/2022] [Accepted: 07/24/2022] [Indexed: 12/24/2022]
Abstract
BACKGROUND Cannabigerol (CBG) is a non-psychoactive phytocannabinoid produced by the plant Cannabis sativa with affinity to various receptors involved in nociception. As a result, CBG is marketed as an over-the-counter treatment for many forms of pain. However, there is very little research-based evidence for the efficacy of CBG as an anti-nociceptive agent. METHODS To begin to fill this knowledge gap, we assessed the anti-nociceptive effects of CBG in C57BL/6 mice using three different models of pain; cisplatin-induced peripheral neuropathy, the formalin test, and the tail-flick assay. RESULTS Using the von Frey test, we found that CBG-attenuated mechanical hypersensitivity evoked by cisplatin-induced peripheral neuropathy in both male and female mice. Additionally, we observed that this CBG-induced reduction in mechanical hypersensitivity was attenuated by the α2 -adrenergic receptor antagonist atipamezole (3 mg/kg, i.p.) and the CB1 R antagonist, AM4113 (3 mg/kg, i.p.), and blocked by the CB2 R antagonist/inverse agonist, SR144528 (10 mg/kg, i.p.). We found that the TRPV1 antagonist, SB705498 (20 mg/kg, i.p.) was unable to prevent CBG actions. Furthermore, we show that CBG:CBD oil (10 mg/kg, i.p.) was more effective than pure CBG (10 mg/kg) at reducing mechanical hypersensitivity in neuropathic mice. Lastly, we show that pure CBG and CBG:CBD oil were ineffective at reducing nociception in other models of pain, including the formalin and tail flick assays. CONCLUSIONS Our findings support the role of CBG in alleviating mechanical hypersensitivity evoked by cisplatin-induced peripheral neuropathy, but highlight that these effects may be limited to specific types of pain. SIGNIFICANCE There are few effective treatments for neuropathic pain and neuropathic pain is projected to increase with the aging population. We demonstrate that CBG (cannabigerol) and CBG:CBD oil attenuate neuropathy-induced mechanical hypersensitivity mice. Second, we identify receptor targets that mediate CBG-induced reduction in mechanical hypersensitivity in neuropathic mice. Third, we demonstrate that an acute injection of CBG is anti-nociceptive specifically for neuropathic pain rather than other forms of pain, including persistent pain and thermal pain.
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Affiliation(s)
- Diana E Sepulveda
- Department of Pharmacology, Penn State University College of Medicine, Hershey, Pennsylvania, USA.,Department of Anesthesiology and Perioperative Medicine, Penn State University College of Medicine, Hershey, Pennsylvania, USA
| | | | - Wesley M Raup-Konsavage
- Department of Pharmacology, Penn State University College of Medicine, Hershey, Pennsylvania, USA
| | - Dongxiao Sun
- Department of Pharmacology, Penn State University College of Medicine, Hershey, Pennsylvania, USA
| | - Kent E Vrana
- Department of Pharmacology, Penn State University College of Medicine, Hershey, Pennsylvania, USA
| | - Nicholas M Graziane
- Department of Pharmacology, Penn State University College of Medicine, Hershey, Pennsylvania, USA.,Department of Anesthesiology and Perioperative Medicine, Penn State University College of Medicine, Hershey, Pennsylvania, USA
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Moretta D, Papamatheakis DG, Morris DP, Giri PC, Blood Q, Murray S, Ramzy M, Romero M, Vemulakonda S, Lauw S, Longo LD, Zhang L, Wilson SM. Long-Term High-Altitude Hypoxia and Alpha Adrenoceptor-Dependent Pulmonary Arterial Contractions in Fetal and Adult Sheep. Front Physiol 2019; 10:1032. [PMID: 31555139 PMCID: PMC6723549 DOI: 10.3389/fphys.2019.01032] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 07/26/2019] [Indexed: 01/01/2023] Open
Abstract
Autonomic innervation of the pulmonary vasculature triggers vasomotor contractility predominately through activation of alpha-adrenergic receptors (α-ARs) in the fetal circulation. Long-term hypoxia (LTH) modulates pulmonary vasoconstriction potentially through upregulation of α1-AR in the vasculature. Our study aimed to elucidate the role of α-AR in phenylephrine (PE)-induced pulmonary vascular contractility, comparing the effects of LTH in the fetal and adult periods on α-AR subtypes and PE-mediated Ca2+ responses and contractions. To address this, we performed wire myography, Ca2+ imaging, and mRNA analysis of pulmonary arteries from ewes and fetuses exposed to LTH or normoxia. Postnatal maturation depressed PE-mediated contractile responses. α2-AR activation contracted fetal vessels; however, this was suppressed by LTH. α1A- and α1B-AR subtypes contributed to arterial contractions in all groups. The α1D-AR was also important to contractility in fetal normoxic vessels and LTH mitigated its function. Postnatal maturity increased the number of myocytes with PE-triggered Ca2+ responses while LTH decreased the percentage of fetal myocytes reacting to PE. The difference between myocyte Ca2+ responsiveness and vessel contractility suggests that fetal arteries are sensitized to changes in Ca2+. The results illustrate that α-adrenergic signaling and vascular function change during development and that LTH modifies adrenergic signaling. These changes may represent components in the etiology of pulmonary vascular disease and foretell the therapeutic potential of adrenergic receptor antagonists in the treatment of pulmonary hypertension.
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Affiliation(s)
- Dafne Moretta
- Pulmonary and Critical Care, School of Medicine, Loma Linda University, Loma Linda, CA, United States
| | | | - Daniel P Morris
- Lawrence D. Longo MD Center for Perinatal Biology, School of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Paresh C Giri
- Pulmonary and Critical Care, School of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Quintin Blood
- Lawrence D. Longo MD Center for Perinatal Biology, School of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Samuel Murray
- Lawrence D. Longo MD Center for Perinatal Biology, School of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Marian Ramzy
- Lawrence D. Longo MD Center for Perinatal Biology, School of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Monica Romero
- Advanced Imaging and Microscopy Core, School of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Srilakshmi Vemulakonda
- Pulmonary and Critical Care, School of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Sidney Lauw
- Lawrence D. Longo MD Center for Perinatal Biology, School of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Lawrence D Longo
- Lawrence D. Longo MD Center for Perinatal Biology, School of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Lubo Zhang
- Lawrence D. Longo MD Center for Perinatal Biology, School of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Sean M Wilson
- Lawrence D. Longo MD Center for Perinatal Biology, School of Medicine, Loma Linda University, Loma Linda, CA, United States.,Advanced Imaging and Microscopy Core, School of Medicine, Loma Linda University, Loma Linda, CA, United States
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Affiliation(s)
- Maria M. Mbugua
- Department of Chemistry & BiochemistryKennesaw State UniversityMariettaGA
| | - Stephanie A. Hill
- Department of Molecular and Cellular BiologyKennesaw State UniversityKennesawGA
| | - Daniel P. Morris
- Department of Molecular and Cellular BiologyKennesaw State UniversityKennesawGA
| | - Jonathan L. McMurry
- Department of Molecular and Cellular BiologyKennesaw State UniversityKennesawGA
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Morris DP, Lei B, Longo LD, Bomsztyk K, Schwinn DA, Michelotti GA. Temporal Dissection of Rate Limiting Transcriptional Events Using Pol II ChIP and RNA Analysis of Adrenergic Stress Gene Activation. PLoS One 2015; 10:e0134442. [PMID: 26244980 PMCID: PMC4526373 DOI: 10.1371/journal.pone.0134442] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 07/10/2015] [Indexed: 12/13/2022] Open
Abstract
In mammals, increasing evidence supports mechanisms of co-transcriptional gene regulation and the generality of genetic control subsequent to RNA polymerase II (Pol II) recruitment. In this report, we use Pol II Chromatin Immunoprecipitation to investigate relationships between the mechanistic events controlling immediate early gene (IEG) activation following stimulation of the α1a-Adrenergic Receptor expressed in rat-1 fibroblasts. We validate our Pol II ChIP assay by comparison to major transcriptional events assessable by microarray and PCR analysis of precursor and mature mRNA. Temporal analysis of Pol II density suggests that reduced proximal pausing often enhances gene expression and was essential for Nr4a3 expression. Nevertheless, for Nr4a3 and several other genes, proximal pausing delayed the time required for initiation of productive elongation, consistent with a role in ensuring transcriptional fidelity. Arrival of Pol II at the 3’ cleavage site usually correlated with increased polyadenylated mRNA; however, for Nfil3 and probably Gprc5a expression was delayed and accompanied by apparent pre-mRNA degradation. Intragenic pausing not associated with polyadenylation was also found to regulate and delay Gprc5a expression. Temporal analysis of Nr4a3, Dusp5 and Nfil3 shows that transcription of native IEG genes can proceed at velocities of 3.5 to 4 kilobases/min immediately after activation. Of note, all of the genes studied here also used increased Pol II recruitment as an important regulator of expression. Nevertheless, the generality of co-transcriptional regulation during IEG activation suggests temporal and integrated analysis will often be necessary to distinguish causative from potential rate limiting mechanisms.
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Affiliation(s)
- Daniel P. Morris
- Center for Perinatal Biology, Loma Linda University, Loma Linda, California, United States of America
- * E-mail:
| | - Beilei Lei
- Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Lawrence D. Longo
- Center for Perinatal Biology, Loma Linda University, Loma Linda, California, United States of America
| | - Karol Bomsztyk
- Department of Medicine, University of Washington, Seattle, Washington, United States of America
| | - Debra A. Schwinn
- Department of Anesthesiology, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States of America
- Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States of America
- Department of Biochemistry, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States of America
| | - Gregory A. Michelotti
- Department of Medicine, Division of Gastroenterology, Duke University Medical Center, Durham, North Carolina, United States of America
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Lei B, Schwinn DA, Morris DP. Stimulation of α1a adrenergic receptors induces cellular proliferation or antiproliferative hypertrophy dependent solely on agonist concentration. PLoS One 2013; 8:e72430. [PMID: 23991110 PMCID: PMC3749976 DOI: 10.1371/journal.pone.0072430] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 07/08/2013] [Indexed: 12/05/2022] Open
Abstract
Stimulation of α1aAdrenergic Receptors (ARs) is known to have anti-proliferative and hypertrophic effects; however, some studies also suggests this receptor can increase cell proliferation. Surprisingly, we find the α1aAR expressed in rat-1 fibroblasts can produce either phenotype, depending exclusively on agonist concentration. Stimulation of the α1aAR by high dose phenylephrine (>10−7 M) induces an antiproliferative, hypertrophic response accompanied by robust and extended p38 activation. Inhibition of p38 with SB203580 prevented the antiproliferative response, while inhibition of Erk or Jnk had no effect. In stark contrast, stimulation of the α1aAR with low dose phenylephrine (∼10−8 M) induced an Erk-dependent increase in cellular proliferation. Agonist-induced Erk phosphorylation was preceded by rapid FGFR and EGFR transactivation; however, only EGFR inhibition blocked Erk activation and proliferation. The general matrix metalloprotease inhibitor, GM6001, blocked agonist induced Erk activation within seconds, strongly suggesting EGFR activation involved extracellular triple membrane pass signaling. Erk activation required little Ca2+ release and was blocked by PLCβ or PKC inhibition but not by intracellular Ca2+ chelation, suggesting Ca2+ independent activation of novel PKC isoforms. In contrast, Ca2+ release was essential for PI3K/Akt activation, which was acutely maximal at non-proliferative doses of agonist. Remarkably, our data suggests EGFR transactivation leading to Erk induced proliferation has the lowest activation threshold of any α1aAR response. The ability of α1aARs to induce proliferation are discussed in light of evidence suggesting antagonistic growth responses reflect native α1aAR function.
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Affiliation(s)
- Beilei Lei
- Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Debra A. Schwinn
- Departments of Anesthesiology, Pharmacology, Biochemistry, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States of America
| | - Daniel P. Morris
- Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, Washington, United States of America
- * E-mail:
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Morris DP, Roush ED, Thompson JW, Moseley MA, Murphy JW, McMurry JL. Kinetic characterization of Salmonella FliK-FlhB interactions demonstrates complexity of the Type III secretion substrate-specificity switch. Biochemistry 2010; 49:6386-93. [PMID: 20586476 DOI: 10.1021/bi100487p] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The bacterial flagellum is a complex macromolecular machine consisting of more than 20 000 proteins, most of which must be exported from the cell via a dedicated Type III secretion apparatus. At a defined point in flagellar morphogenesis, hook completion is sensed and the apparatus switches substrate specificity type from rod and hook proteins to filament ones. How the switch works is a subject of intense interest. FliK and FlhB play central roles. In the present study, two optical biosensing methods were used to characterize FliK-FlhB interactions using wild-type and two variant FlhBs from mutants with severe flagellar structural defects. Binding was found to be complex with fast and slow association and dissociation components. Surprisingly, wild-type and variant FlhBs had similar kinetic profiles and apparent affinities, which ranged between 1 and 10.5 microM, suggesting that the specificity switch is more complex than presently understood. Other binding experiments provided evidence for a conformational change after binding. Liquid chromatography-mass spectrometry (LC-MS) and NMR experiments were performed to identify a cyclic intermediate product whose existence supports the mechanism of autocatalytic cleavage at FlhB residue N269. The present results show that while autocatalytic cleavage is necessary for proper substrate specificity switching, it does not result in an altered interaction with FliK, strongly suggesting the involvement of other proteins in the mechanism.
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Affiliation(s)
- Daniel P Morris
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA
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Lei B, Morris DP, Smith MP, Schwinn DA. Lipid rafts constrain basal alpha(1A)-adrenergic receptor signaling by maintaining receptor in an inactive conformation. Cell Signal 2009; 21:1532-9. [PMID: 19520158 DOI: 10.1016/j.cellsig.2009.06.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2009] [Revised: 05/20/2009] [Accepted: 06/01/2009] [Indexed: 12/16/2022]
Abstract
We have reported that the alpha(1A)-adrenergic receptor (alpha(1A)AR) in rat-1 fibroblasts is a lipid raft protein. Here we examined whether disrupting lipid rafts by methyl-beta-cyclodextrin (MCD) sequestration of cholesterol affects alpha(1A)AR signaling. Unexpectedly, MCD increased alpha(1A)AR-dependent basal inositol phosphate formation and p38 mitogen-activated protein kinase activation in a cholesterol-dependent manner. It also initiated internalization of surface alpha(1A)AR, which was partially blocked by receptor inhibition. Binding assays revealed MCD-mediated increases in receptor agonist affinity as well as reciprocal decreases in inverse agonist affinity, a behavior that is usually interpreted as a shift toward the active receptor conformation. In untreated cells a fraction of the receptor was found to be present in preassociated receptor/G protein complexes, which rapidly dissociate upon receptor stimulation. Consistent with MCD-induced signaling, raft disruption resulted in an increase in receptor/G protein complexes. These results strongly suggest that lipid rafts constrain basal alpha(1A)AR activity; however, preassembled receptor/G protein complexes could still provide a mechanism for accelerating alpha(1A)AR signaling following stimulation.
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Affiliation(s)
- Beilei Lei
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA.
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Hui D, Nawaz M, Morris DP, Edwards MR, Saunders BR. Study of pH-triggered heteroaggregation and gel formation within mixed dispersions. J Colloid Interface Sci 2008; 324:110-7. [DOI: 10.1016/j.jcis.2008.05.035] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2008] [Revised: 05/16/2008] [Accepted: 05/19/2008] [Indexed: 11/28/2022]
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Morris DP, Lei B, Wu YX, Michelotti GA, Schwinn DA. The alpha1a-adrenergic receptor occupies membrane rafts with its G protein effectors but internalizes via clathrin-coated pits. J Biol Chem 2008; 283:2973-85. [PMID: 18048357 PMCID: PMC2566898 DOI: 10.1074/jbc.m705795200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The alpha(1a)-adrenergic receptor (alpha(1a)AR) occupies intracellular and plasma membranes in both native and heterologous expression systems. Based on multiple independent lines of evidence, we demonstrate the alpha(1a)AR at the cell surface occupies membrane rafts but exits from rafts following stimulation. In non-detergent raft preparations, basal alpha(1a)AR is present in low density membrane rafts and colocalizes with its G protein effectors on density gradients. Raft disruption by cholesterol depletion with methyl-beta-cyclodextrin eliminates these light rafts. To confirm the presence of the alpha(1a)AR in plasma membrane rafts, fluorescence resonance energy transfer measurements were used to demonstrate colocalization of surface receptor and the raft marker, cholera toxin B. This colocalization was largely lost following alpha(1a)AR stimulation with phenylephrine. Similarly, receptor stimulation causes exit of the alpha(1a)AR from light rafts within 3-10 min in contrast to the G proteins, which largely remain in light rafts. Importantly, this delayed exit of the alpha(1a)AR suggests acute receptor signaling and desensitization occur entirely within rafts. Interestingly, both confocal analysis and measurement of surface alpha(1a)AR levels indicate modest receptor internalization during the 10 min following stimulation, suggesting most of the receptor has entered non-raft plasma membrane. Nevertheless, activation does increase the rate of receptor internalization as does disruption of rafts with methyl-beta-cyclodextrin, suggesting raft exit enables internalization. Confocal analysis of surface-labeled hemagglutinin-alpha(1a)AR reveals that basal and stimulated receptor occupies clathrin pits in fixed cells consistent with previous indirect evidence. The evidence presented here strongly suggests the alpha(1a)AR is a lipid raft protein under basal conditions and implies agonist-mediated signaling occurs from rafts.
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Affiliation(s)
- Daniel P Morris
- Department of Anesthesiology, Duke University Medical Center, 595 LaSalle Street, Durham, NC 27710, USA.
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Michelotti GA, Brinkley DM, Morris DP, Smith MP, Louie RJ, Schwinn DA. Epigenetic regulation of human alpha1d-adrenergic receptor gene expression: a role for DNA methylation in Sp1-dependent regulation. FASEB J 2007; 21:1979-93. [PMID: 17384146 PMCID: PMC2279228 DOI: 10.1096/fj.06-7118com] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
A growing body of evidence implicates alpha1-adrenergic receptors (alpha1ARs) as potent regulators of growth pathways. The three alpha1AR subtypes (alpha1aAR, alpha1bAR, alpha1dAR) display highly restricted tissue expression that undergoes subtype switching with many pathological stimuli, the mechanistic basis of which remains unknown. To gain insight into transcriptional pathways governing cell-specific regulation of the human alpha1dAR subtype, we cloned and characterized the alpha1dAR promoter region in two human cellular models that display disparate levels of endogenous alpha1dAR expression (SK-N-MC and DU145). Results reveal that alpha1dAR basal expression is regulated by Sp1-dependent binding of two promoter-proximal GC boxes, the mutation of which attenuates alpha1dAR promoter activity 10-fold. Mechanistically, chromatin immunoprecipitation data demonstrate that Sp1 binding correlates with expression of the endogenous gene in vivo, correlating highly with alpha1dAR promoter methylation-dependent silencing of both episomally expressed reporter constructs and the endogenous gene. Further, analysis of methylation status of proximal GC boxes using sodium bisulfite sequencing reveals differential methylation of proximal GC boxes in the two cell lines examined. Together, the data support a mechanism of methylation-dependent disruption of Sp1 binding in a cell-specific manner resulting in repression of basal alpha1dAR expression.
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MESH Headings
- Azacitidine/analogs & derivatives
- Azacitidine/pharmacology
- Base Sequence
- Cell Line, Tumor
- Chromatin/chemistry
- DNA (Cytosine-5-)-Methyltransferases/antagonists & inhibitors
- DNA Methylation
- Decitabine
- Gene Expression Regulation
- Gene Silencing
- Humans
- Immunoprecipitation
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Promoter Regions, Genetic/genetics
- Protein Binding
- RNA, Messenger/biosynthesis
- Receptors, Adrenergic, alpha-1/biosynthesis
- Receptors, Adrenergic, alpha-1/genetics
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/genetics
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Analysis, DNA
- Sp1 Transcription Factor/metabolism
- Sulfites/pharmacology
- Transcription, Genetic
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Affiliation(s)
- Gregory A Michelotti
- Department of Pharmacology/Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
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Morris DP, Michelotti GA, Schwinn DA. Evidence that phosphorylation of the RNA polymerase II carboxyl-terminal repeats is similar in yeast and humans. J Biol Chem 2005; 280:31368-77. [PMID: 16012166 PMCID: PMC2277102 DOI: 10.1074/jbc.m501546200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Using an improved chromatin immunoprecipitation assay designed to increase immunoprecipitation efficiency, we investigated changes in RNA polymerase II (Pol II) density and carboxyl-terminal domain (CTD) phosphorylation during transcription of the cyclophilin A (PPIA), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and several androgen-responsive genes in LNCaP cells. As generally observed in higher eukaryotes, promoter proximal pausing of Pol II appeared to occur on the PPIA and GAPDH genes, but apparently not on the androgen-responsive genes PSA and NKX3-1. Unlike some mammalian studies, we found that the CTD of Pol II in promoter regions contains little phosphorylation at Ser-2 of the heptad repeat, suggesting that Ser-2 phosphorylation is not involved in polymerase exit from the promoter region. In contrast, Pol II near the promoter displayed high levels of Ser-5 phosphorylation, which decreased as polymerase transcribed beyond the promoter region of the PPIA and GAPDH genes. However, total Pol II levels appear to decrease as much or more, suggesting that Ser-5 phosphorylation is maintained. In support of this conclusion, a phosphoserine 5-specific antibody quantitatively immunoprecipitates native hyperphosphorylated Pol II, suggesting that all polymerase with phosphoserine 2 also contains phosphoserine 5. Given reports indicating that phosphoserine 5 is present during elongation in yeast, our data suggest that gross changes in CTD phosphorylation patterns during transcription may be more conserved in yeast and humans than recognized previously.
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Affiliation(s)
- Daniel P Morris
- Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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Lei B, Morris DP, Smith MP, Svetkey LP, Newman MF, Rotter JI, Buchanan TA, Beckstrom-Sternberg SM, Green ED, Schwinn DA. Novel human alpha1a-adrenoceptor single nucleotide polymorphisms alter receptor pharmacology and biological function. Naunyn Schmiedebergs Arch Pharmacol 2005; 371:229-39. [PMID: 15900517 PMCID: PMC2367253 DOI: 10.1007/s00210-005-1019-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2004] [Accepted: 12/21/2004] [Indexed: 11/26/2022]
Abstract
We identified nine naturally-occurring human single nucleotide polymorphisms (SNPs) in the alpha(1a)-adrenoceptor (alpha(1a)AR) coding region, seven of which result in amino acid change. Utilizing rat-1 fibroblasts stably expressing wild type alpha(1a)AR or each SNP at both high and low levels, we investigated the effect of these SNPs on receptor function. Compared with wild type, two SNPs (R166K, V311I) cause a decrease in binding affinity for agonists norepinephrine, epinephrine, and phenylephrine, and also shift the dose-response curve for norepinephrine stimulation of inositol phosphate (IP) production to the right (reduced potency) without altering maximal IP activity. In addition, SNP V311I and I200S display altered antagonist binding. Interestingly, a receptor with SNP G247R (located in the third intracellular loop) displays increased maximal receptor IP activity and stimulates cell growth. The increased receptor signaling for alpha(1a)AR G247R is not mediated by altered ligand binding or a deficiency in agonist-mediated desensitization, but appears to be related to enhanced receptor-G protein coupling. In conclusion, four naturally-occurring human alpha(1a)AR SNPs induce altered receptor pharmacology and/or biological activity. This finding has potentially important implications in many areas of medicine and can be used to guide alpha(1a)AR SNP choice for future clinical studies.
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MESH Headings
- Adrenergic alpha-Agonists/pharmacology
- Adrenergic alpha-Antagonists/pharmacology
- Amino Acid Sequence
- Amino Acid Substitution
- Animals
- Cell Division/genetics
- Cells, Cultured
- Dose-Response Relationship, Drug
- GTP-Binding Proteins/metabolism
- Humans
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Phosphoric Monoester Hydrolases/metabolism
- Polymorphism, Single Nucleotide
- Radioligand Assay
- Rats
- Receptors, Adrenergic, alpha-1/drug effects
- Receptors, Adrenergic, alpha-1/genetics
- Receptors, Adrenergic, alpha-1/metabolism
- Signal Transduction
- Transfection
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Affiliation(s)
- Beilei Lei
- Department of Anesthesiology, Duke University Medical Center, Box 3094 Durham, NC, 27710, USA
- Department of Pharmacology/Cancer Biology Duke University Medical Center, Durham, NC, USA
| | - Daniel P. Morris
- Department of Anesthesiology, Duke University Medical Center, Box 3094 Durham, NC, 27710, USA
- Department of Pharmacology/Cancer Biology Duke University Medical Center, Durham, NC, USA
| | - Michael P. Smith
- Department of Anesthesiology, Duke University Medical Center, Box 3094 Durham, NC, 27710, USA
- Department of Pharmacology/Cancer Biology Duke University Medical Center, Durham, NC, USA
| | - Laura P. Svetkey
- Department of Medicine, Duke University Medical Center, Durham, NC, USA
| | - Mark F. Newman
- Department of Anesthesiology, Duke University Medical Center, Box 3094 Durham, NC, 27710, USA
| | - Jerome I. Rotter
- Department of Medicine, Cedars-Sinai Medical Center and the University of California, Los Angeles, CA, USA
- Department of Pediatrics, Cedars-Sinai Medical Center and the University of California, Los Angeles, CA, USA
- Department of Human Genetics, Cedars-Sinai Medical Center and the University of California, Los Angeles, CA, USA
| | - Thomas A. Buchanan
- Department of Medicine, University of Southern California, Los Angeles, CA, USA
| | | | - Eric D. Green
- Genome Technology Branch and NIH Intramural Sequencing Center, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - Debra A. Schwinn
- Department of Anesthesiology, Duke University Medical Center, Box 3094 Durham, NC, 27710, USA, e-mail: , Tel.: +1-919-6814781, Fax: +1-919-6814776
- Department of Pharmacology/Cancer Biology Duke University Medical Center, Durham, NC, USA
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Morris DP, Price RR, Smith MP, Lei B, Schwinn DA. Cellular trafficking of human alpha1a-adrenergic receptors is continuous and primarily agonist-independent. Mol Pharmacol 2004; 66:843-54. [PMID: 15258254 DOI: 10.1124/mol.104.000430] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Alpha1a-adrenergic receptors (alpha1aARs) are present intracellularly and at the cell surface in cultured and natural cell models, where they are subject to agonist-mediated desensitization and internalization. To explore alpha1aAR trafficking, a hemagglutinin (HA)-tagged alpha1aAR/enhanced green fluorescent protein (EGFP) fusion protein was expressed in rat-1 fibroblasts and tracked by EGFP fluorescence and antibody labeling of surface receptors. Confocal analysis of antibody-labeled surface receptors revealed unexpected constitutive internalization in the absence of agonist stimulation. In partial agreement, the inverse agonist prazosin also caused a modest 20 +/- 2% increase in surface receptor levels, suggesting a partial block of constitutive internalization caused by decreased basal activation. However, prazosin was unable to prevent internalization of antibody-tagged surface receptors observed by confocal microscopy or cause obvious redistribution of intracellular receptor to the surface, suggesting that the alpha1aAR is internalizing even in a basal-inactive state. In contrast to the alpha1aAR, surface labeling of an HA-tagged alpha1b-EGFP fusion protein did not result in any apparent constitutive internalization. Constitutive internalization of the alpha1aAR seems to occur alongside reversible agonist-induced internalization, and both seem to involve clathrin-mediated endocytosis but not degradation in lysozymes. Surface receptor density must be maintained by recycling, because the protein synthesis inhibitor cycloheximide has no effect on total or surface receptor density in agonist-treated or untreated cells for 6 h. Constitutive agonist-independent trafficking of alpha1aARs may provide a novel mechanism by which an internal pool of alpha1aARs are maintained and recycled to allow continuous agonist-induced signaling.
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Affiliation(s)
- Daniel P Morris
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA
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17
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Morris DP, Bance M, Van Wijhe RG. Vibration characteristics and function of atelectatic segments in the tympanic membrane in fresh human cadaveric temporal bones. ACTA ACUST UNITED AC 2004; 29:133-7. [PMID: 15113296 DOI: 10.1111/j.1365-2273.2004.00799.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dimeric segments are commonly encountered in otological practice. They may be associated with a mild conductive hearing loss and often coexist with other tympanic membrane and middle ear abnormalities. Some otologists have advocated surgical management but the consequences of dimeric segment stiffening, shielding or excision and grafting on acoustic transfer to the stapes footplate has been poorly explored. In this study, laser Doppler vibrometry was used to measure vibrations at the tympanic membrane and the stapes footplate in the fresh cadaveric human temporal bone. The dimeric segment vibrates more than the adjacent, thicker normal tympanic membrane. Shielding or excision and grafting of the dimeric segment with thicker and stiffer materials has little effect on displacement at the stapes footplate.
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Affiliation(s)
- D P Morris
- The Ear and Auditory Research Laboratory (EAR Lab.), Dalhousie University, Halifax, Nova Scotia, Canada
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Price RR, Morris DP, Biswas G, Smith MP, Schwinn DA. Acute agonist-mediated desensitization of the human alpha 1a-adrenergic receptor is primarily independent of carboxyl terminus regulation: implications for regulation of alpha 1aAR splice variants. J Biol Chem 2002; 277:9570-9. [PMID: 11781325 DOI: 10.1074/jbc.m111762200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Despite important roles in myocardial hypertrophy and benign prostatic hyperplasia, little is known about acute effects of agonist stimulation on alpha(1a)-adrenergic receptor (alpha(1a)AR) signaling and function. Regulatory mechanisms are likely complex since 12 distinct human alpha(1a)AR carboxyl-terminal splice variants have been isolated. After determining the predominance of the alpha(1a-1)AR isoform in human heart and prostate, we stably expressed an epitope-tagged alpha(1a-1)AR cDNA in rat-1 fibroblasts and subsequently examined regulation of signaling, phosphorylation, and internalization of the receptor. Human alpha(1a)AR-mediated inositol phosphate signaling is acutely desensitized in response to both agonist and phorbol 12-myristate 13-acetate (PMA) exposure. Concurrent with desensitization, alpha(1a)ARs in (32)P(i)-labeled cells are rapidly phosphorylated in response to both NE and PMA stimulation. Despite the ability of PKC to desensitize alpha(1a)ARs when directly activated with PMA, inhibitors of PKC have no effect on agonist-mediated desensitization. In contrast, involvement of GRK kinases is suggested by the ability of GRK2 to desensitize alpha(1a)ARs. Internalization of cell surface alpha(1a)ARs also occurs in response to agonist stimulation (but not PKC activation), but is initiated more slowly than receptor desensitization. Significantly, deletion of the alpha(1a)AR carboxyl terminus has no effect on receptor internalization or either agonist-induced or GRK-mediated receptor desensitization. Because mechanisms underlying acute agonist-mediated regulation of human alpha(1a)ARs are primarily independent of the carboxyl terminus, they may be common to all functional alpha(1a)AR isoforms.
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Affiliation(s)
- R Reyn Price
- Department of Pharmacology, Duke University Medical Center, Durham, North Carolina 27710, USA
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22
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Abstract
It is essential for the Otologist in training to become familiar with the anatomy of the temporal bone. Generations of trainees have acquired this knowledge, together with basic surgical skills and techniques by dissection of cadaver temporal bones. In recent years, however, the supply of temporal bones for dissection has become a contentious issue in many British hospitals. Media and public attention has recently focused on issues surrounding the retention of human tissues following post-mortem examinations. In response, the Chief Medical Officer, the Royal College of Pathologists in the UK, the Faculty of Pathology of the Royal College of Physicians in Ireland, the British Medical Association, and other bodies have issued new guidelines that are of relevance to the Otolaryngologist. This paper gives details of some of the UK guidelines and where they can be accessed. A copy of the Royal College of Pathologists preferred post-mortem consent form is presented. The authors' experience in Manchester is discussed and details of an information leaflet on the subject of temporal bone donation are given. It is concluded that, with knowledge of the existing guidelines and good communication with other hospital colleagues, as well as families of the deceased, it is still possible legally to obtain temporal bones for dissection.
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Affiliation(s)
- D P Morris
- Department of Otolaryngology, Head and Neck Surgery, Manchester Royal Infirmary, Oxford Road, Manchester, UK.
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23
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Myers JK, Morris DP, Greenleaf AL, Oas TG. Phosphorylation of RNA polymerase II CTD fragments results in tight binding to the WW domain from the yeast prolyl isomerase Ess1. Biochemistry 2001; 40:8479-86. [PMID: 11456485 DOI: 10.1021/bi0027884] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The yeast prolyl isomerase, Ess1, has recently been shown to interact via its WW domain with the hyperphosphorylated form of the RNA polymerase II C-terminal domain (CTD). We have investigated folding of the Ess1 WW domain and its binding to peptides representing the CTD by circular dichroism and fluorescence. Ess1 WW folds and unfolds reversibly, but in the absence of ligand is only marginally stable with a melting temperature of 19 degrees C. The WW domain is stabilized by the addition of anionic ligands, namely, chloride, inorganic phosphate, phosphoserine, and phosphorylated CTD peptides. Dissociation constants were measured to be 70--100 microM for CTD peptides phosphorylated at one serine, and 16--21 microM for peptides with two or more phosphorylated serines. Weaker or no affinity was observed for nonphosphorylated CTD peptides. There is surprisingly little difference in the affinity for peptides phosphorylated at Ser 2 or Ser 5 of the consensus repeat, or for peptides with different patterns of multiple phosphorylation. The binding of Ess1 to phosphorylated CTD peptides is consistent with a model wherein the WW domain positions Ess1 to catalyze isomerization of the many pSer--Pro peptide bonds in the phosphorylated CTD. We suggest that cis/trans isomerization of prolyl peptide bonds plays a crucial role in CTD function during eukaryotic transcription.
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Affiliation(s)
- J K Myers
- Department of Biochemistry, Box 3711, Duke University Medical Center, Durham, North Carolina 27710, USA
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24
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Banerjee SS, Morris DP, Rothera MP, Routledge RC. Relapsing polychondritis associated with monoclonal gammopathy in a patient with myelodysplastic syndrome. J Laryngol Otol 2001; 115:482-4. [PMID: 11429073 DOI: 10.1258/0022215011907983] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Relapsing polychondritis is a rare condition characterized by inflammation and subsequent degeneration of cartilages. Deformity of the pinna, nasal saddling and stridor due to involvement of the cartilages of the respiratory tract may lead to patients being referred to the otolaryngologist for initial assessment and further management. Recent observations have suggested that relapsing polychondritis may occur as a paraneoplastic phenomenon in cases of myelodysplasia. The case of a patient with relapsing polychondritis, myelodysplastic syndrome and a monoclonal gammopathy is presented. The authors highlight the apparent existence of this association and encourage otolaryngologists to consider such possible links when cases of relapsing polychondritis present to the outpatients department.
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Affiliation(s)
- S S Banerjee
- Department of Otolaryngology, Hope Hospital, Salford, UK
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25
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Malik T, Luff D, Morris DP, Curley J. A modification to aid open tracheostomy. J R Coll Surg Edinb 2001; 46:190. [PMID: 11478026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
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Abstract
The authors describe the adaptation of a Montgomery T-tube laryngo-tracheal stent to incorporate an uncuffed fenestrated Shiley tracheostomy tube in the management of a complex case of subglottic stenosis. The combined 'trache-stent' provided a secure, unobstructed airway and optimal phonation. The presence of a removable inner tube facilitated cleaning and reduced patient anxiety regarding the perceived risks of stent obstruction with dried secretions. The combined 'trache-stent' was upsized at four weeks with minimal evidence of local granulation formation. The device was removed entirely six weeks later after direct laryngoscopy reconfirmed the above findings. Almost two years later the patient retains a good voice and airway using a simple fenestrated tracheostomy tube and speaking valve. The subglottic area is stable and the patient has returned to full-time employment.
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Affiliation(s)
- D P Morris
- Department of Otolaryngology, Hope Hospital, Salford and The Royal Manchester Children's Hospital, Pendlebury, UK.
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27
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Abstract
We showed previously that the WW domain of the prolyl isomerase, Ess1, can bind the phosphorylated carboxyl-terminal domain (phospho-CTD) of the largest subunit of RNA Polymerase II. Analysis of phospho-CTD binding by four other WW domain-containing Saccharomyces cerevisiae proteins indicates the splicing factor, Prp40, and the RNA polymerase II ubiquitin ligase, Rsp5, can also bind the phospho-CTD. The identification of Prp40 as a phospho-CTD binding protein represents the first demonstration of direct interaction between a documented splicing factor and the phospho-CTD. Domain dissection studies reveal that phospho-CTD binding occurs at multiple locations in Prp40, including sites in both the WW and FF domain regions. Because the conserved repeats of the CTD make it an ideal ligand for multi-site binding events, the implications of multi-site binding are discussed. Our data suggest a mechanism by which the phospho-CTD of elongating RNA polymerase II facilitates commitment complex formation by juxtaposing the 5' and 3' splice sites.
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Affiliation(s)
- D P Morris
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA
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Morris DP, Rothera MP. The application of computer-enhanced imaging to improve preoperative counselling and informed consent in children considering bone anchored auricular prosthesis surgery. Int J Pediatr Otorhinolaryngol 2000; 55:181-6. [PMID: 11035174 DOI: 10.1016/s0165-5876(00)00382-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVES Bone anchored auricular prostheses have become a valuable option in the treatment of congenital and acquired deformities of the pinna. However, preoperative counselling and informed consent remains a challenging issue. Until recently it has been difficult to provide the child with a realistic prediction of their own postoperative appearance. This is particularly relevant when a remnant pinna needs to be excised prior to the second stage. The potential for psychological repercussions and the possibility that remnant excision might compromise future autologous tissue reconstruction make it imperative that the decision to proceed with surgery is founded on the best possible information. METHODS The authors describe the use of computer enhanced images using the Adobe Photoshop (Apple Mac. Inc.) software package to provide such a preview. This technique is used in the outpatient clinic as an adjunct to counselling provided by clinic staff and is reinforced by meeting children who have already enrolled on to the implant programme. Children are encouraged to follow the stages of their planned operation on the computer screen, providing an accurate insight into the physical consequences of surgery. RESULTS Our experiences suggest that this approach has encouraged a better qualitative understanding of implant surgery which has helped to foster the on-going commitment that is required to maintain a long-lasting, trouble-free implant site. CONCLUSIONS This application of the Adobe Photoshop package has strengthened our basis for a personal informed consent and has provided an opportunity to lessen the adverse psychological consequences of such irreversible surgery. It is commended for its simplicity as it employs established software to enhance photographic prints or slides taken from the child's clinical records.
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Affiliation(s)
- D P Morris
- Department of Paediatric Otolaryngology, The Royal Manchester Children's Hospital, Pendlebury, UK.
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Abstract
Amyloidosis of the upper aerodigestive tract is relatively rare. A case of localized amyloidosis involving all components of Waldeyer's ring with added laryngeal involvement is described. This has not been previously reported. A literature review of this conditions is presented.
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Affiliation(s)
- K M Green
- Department of Otolaryngology, Fairfield General Hospital, Bury, UK
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30
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Morris DP, Saeed SR. The common causes of hearing loss in adults. Practitioner 2000; 244:70-4, 76-7, 79-80 passim. [PMID: 10892040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
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Morris DP, Phatnani HP, Greenleaf AL. Phospho-carboxyl-terminal domain binding and the role of a prolyl isomerase in pre-mRNA 3'-End formation. J Biol Chem 1999; 274:31583-7. [PMID: 10531363 DOI: 10.1074/jbc.274.44.31583] [Citation(s) in RCA: 123] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A phospho-carboxyl-terminal domain (CTD) affinity column created with yeast CTD kinase I and the CTD of RNA polymerase II was used to identify Ess1/Pin1 as a phospho-CTD-binding protein. Ess1/Pin1 is a peptidyl prolyl isomerase involved in both mitotic regulation and pre-mRNA 3'-end formation. Like native Ess1, a GSTEss1 fusion protein associates specifically with the phosphorylated but not with the unphosphorylated CTD. Further, hyperphosphorylated RNA polymerase II appears to be the dominant Ess1 binding protein in total yeast extracts. We demonstrate that phospho-CTD binding is mediated by the small WW domain of Ess1 rather than the isomerase domain. These findings suggest a mechanism in which the WW domain binds the phosphorylated CTD of elongating RNA polymerase II and the isomerase domain reconfigures the CTD though isomerization of proline residues perhaps by a processive mechanism. This process may be linked to a variety of pre-mRNA maturation events that use the phosphorylated CTD, including the coupled processes of pre-mRNA 3'-end formation and transcription termination.
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Affiliation(s)
- D P Morris
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA
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Abstract
We describe the technique of implant-site split-skin grafting for the bone-anchored hearing aid (BAHA). Twenty-five patients have undergone this procedure (20 adults and five children) since 1993 with a minimum follow-up of 1 year. Fifteen adults were operated upon as single stage surgery, all other cases (including all children) were performed in two stages. In four patients (16%) significant early graft inflammation was encountered which settled with outpatient treatment. In one the abutment had to be temporarily removed to allow the graft to settle. All patients now have a stable graft site. This surgical technique is straightforward and a separate graft donor site is avoided. It would appear this technique results in a stable BAHA graft site with low associated morbidity.
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Morris DP, Luff DA, Hargreaves SP, Rothera MP. Bones of contention. The supply of temporal bones for dissection: the legalities, problems and solutions. J Laryngol Otol 1998; 112:1138-41. [PMID: 10209607 DOI: 10.1017/s0022215100142689] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Temporal bone dissection is considered to be an important aspect of the otological training of the Specialist Registrar with dissection skills being formally assessed in the Intercollegiate Fellowship Examination. However the procurement of cadaveric specimens suitable for dissection may be fraught with difficulties. The authors take an historical perspective to clarify the existing legal issues and outline the means available to improve supply.
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Affiliation(s)
- D P Morris
- Department of Otolaryngology, Hope Hospital, Salford, UK
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Abstract
The CTD (carboxy-terminal repeat domain) of the largest subunit of RNA Polymerase II in most eukaryotes consists of from 26 to 52 seven amino acid repeats, the consensus sequence of which is YSPTSPS. Even though this consensus repeat does not contain residues that are normally protonated under the conditions used for positive ion electrospray mass spectrometry, we find that the CTD acquires about one proton per repeat when analyzed by this procedure. We have termed this phenomenon superprotonation. Superprotonation is apparently a property of the consensus sequence as the repeat peptide, (YSPTSPS)4, is superprotonated whereas other proteins and the repeat peptides (YSPTSPK)4, (YSPTSPR)4 and (YSPTAPR)4 are not. The highly conserved nature of the contiguous consensus repeats in organisms ranging from yeast to mammals implies that the functionally significant behavior of the domain is easily perturbed. We propose that CTD superprotonation is a manifestation of a unique biophysical property that will influence and could be the basis for consensus repeat function in vivo.
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Affiliation(s)
- D P Morris
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina, 27710, USA
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Morris DP, Lee JM, Sterner DE, Brickey WJ, Greenleaf AL. Assaying CTD kinases in vitro and phosphorylation-modulated properties of RNA polymerase II in vivo. Methods 1997; 12:264-75. [PMID: 9237170 DOI: 10.1006/meth.1997.0478] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The functional properties of RNA polymerase II are modulated by hyperphosphorylation of its unique C-terminal repeat domain (CTD). A number of enzymes with CTD kinase activity have been identified, and correlations between CTD phosphorylation and RNA polymerase II function have been made. Here we describe methods for assaying CTD kinases and for characterizing them enzymologically. In addition we present approaches for studying phosphorylation-mediated behavior of chromosome-associated RNA polymerase II by using CTD-directed, phosphorylation state-sensitive antibodies and in situ localization techniques. The methods described here should, in conjunction with genetic approaches, contribute to elucidating the physiological roles of CTD kinases.
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Affiliation(s)
- D P Morris
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA
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Abstract
Factor IX activation by factor XIa is thought to proceed through the singly-cleaved free intermediate, factor IX alpha. However, we observed no intermediate development during factor IX activation by factor XIa when using a low substrate to enzyme ratio (44:1 mol/mol). This result can be explained by one of two mechanisms: (1) factor XIa-catalyzed activation proceeds via a singly-cleaved free intermediate with a much higher efficiency of cleavage than factor IX zymogen, or (2) the reaction occurs without free intermediate generation, whereby factor XIa makes both proteolytic cleavages in a single substrate molecule before releasing the final product (processive mechanism). We compared the factor XIa cleavage rates of free factor IX alpha and factor IXa alpha with that of factor IX zymogen. In contrast to the requirements of mechanism (1), the cleavage rate constants of factor IX zymogen, factor IX alpha, and factor IXa alpha were similar: 0.38 +/- 0.02 s(-1), 0.34 +/- 0.05 s(-1), and 0.27 +/- 0.01 s(-1), respectively. It seems likely that factor XIa-generated intermediates observed under some reaction conditions are produced through the occasional failure of a processive mechanism. Indeed, in reactions using a high substrate to enzyme ratio (1900:1 mol/mol), we observed some factor IX alpha development; however, the pattern of intermediate and product development over time was inconsistent with a mechanism involving an obligate intermediate. Rather, it corresponded to behavior expected from a processive mechanism undergoing a consistent low failure. We conclude that factor XIa-catalyzed activation of factor IX proceeds via a processive mechanism without release of a free intermediate.
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Affiliation(s)
- A S Wolberg
- Department of Biology, University of North Carolina, Chapel Hill 27599-3280, USA
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Morris DP, Stevens RD, Wright DJ, Stafford DW. Processive post-translational modification. Vitamin K-dependent carboxylation of a peptide substrate. J Biol Chem 1995; 270:30491-8. [PMID: 8530480 DOI: 10.1074/jbc.270.51.30491] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Mass spectrometry has been used to demonstrate that vitamin K-dependent carboxylation is a processive post-translational modification (i.e. multiple carboxylations occur during a single association between enzyme and substrate). Purified vitamin K-dependent carboxylase can carboxylate as many as 12 glutamate residues in FIXQ/S, a peptide substrate based on amino acids -18 to 41 of the human blood clotting enzyme factor IX. Mass spectrometry was used to determine the number of gamma-carboxyl groups added to FIXQ/S by the carboxylase during an in vitro reaction. Despite the fact that most substrate molecules in a reaction were uncarboxylated, almost all carboxylated FIXQ/S molecules were carboxylated many times. This observation can only be explained by two types of mechanisms. In a processive mechanism, multiple carboxylations could occur during a single substrate binding event. Alternatively, a distributive mechanism could result in the observed behavior if the initial carboxylation event results in a substrate that is additionally carboxylated far more efficiently than the uncarboxylated FIXQ/S. Kinetic experiments and arguments were used to show that the vitamin K-dependent carboxylase is not distributive but rather is one of the first well documented examples of an enzyme that catalyzes a processive post-translation modification.
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Affiliation(s)
- D P Morris
- Department of Biology, University of North Carolina, Chapel Hill 27599-3280, USA
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Fisher EW, Morris DP, Biemans JM, Palmer CR, Lund VJ. Practical aspects of acoustic rhinometry: problems and solutions. Rhinology 1995; 33:219-23. [PMID: 8919215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Acoustic rhinometry now has an established place in the rhinology laboratory as a measure of nasal geometry. We aimed to investigate several aspects of technique in order to offer some guidance on preferred procedures. We studied the effects of nosepiece seal quality, nosepiece aperture diameter, angle of inclination of the wave tube (in two planes), palate position and inter-observer variation on the nasal area-distance function. One hundred nasal cavities in adults and children were examined: 50 normal and 50 pathological. Each factor was examined intensively in 20 cavities, and reproducibility data obtained on all 100 cavities. The baseline mean coefficient of variation for nasal cavity volume (V1) was 6% and for minimum cross-sectional area (MCA) was 8%. Altering the angle of incidence of the wave tube in the axial and coronal planes caused considerable change in the traces from the anterior nasal cavity, including the I- and C-notches, and affected the MCA significantly (p < 0.01, Wilcoxon signed rank test). Using a small nosepiece aperture accentuated the I-notch, and the nosepiece in some cases became the site of the minimal area. Addition of a silicone-based sealant to the standard nosepiece caused a mean reduction of 14.3% in nasal volume, if the seal quality was suspected to be suboptimal. Nasopharyngeal volume decreased by a mean of 28.6% when the palate is raised by the modified Valsalva manoeuvre, and no difference was found between quiet oral respiration and cessation of nasal respiration. Acoustic rhinometry is sensitive to minor changes in the details of technique. We recommend using an intermediate range of angles in both planes, the addition of a sealant where the nosepiece seal is suspect, use of newer improved nosepieces and synchronizing readings with either cessation of nasal respiration or with quiet oral respiration. There is a pressing need for international agreement on such details if collaboration and clinical application of acoustic rhinometry is to flourish.
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Affiliation(s)
- E W Fisher
- Department of Otorhinolaryngology, Addenbrooke's Hospital, Cambridge, United Kingdom
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Morris DP, Ballagh RH, Hong A, Moffat DA, Hardy DG. Thrombosed posterior-inferior cerebellar artery aneurysm: a rare cerebellopontine angle tumour. J Laryngol Otol 1995; 109:429-30. [PMID: 7798000 DOI: 10.1017/s0022215100130348] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A case report of a thrombosed posterior-inferior cerebellar artery aneurysm is described. The tumour masqueraded as a vestibular schwannoma on imaging but the presenting features were unusual, the facial pain and weakness predominating despite well preserved hearing. This is an example of a rare cerebellopontine angle tumour and highlights the need for suspicion when lesions present atypically.
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Affiliation(s)
- D P Morris
- Department of Otoneurosurgery, Addenbrooke's Hospital, Cambridge
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Abstract
The ability of acoustic rhinometry to detect objects of defined size in nasal cavities has hitherto been investigated only in cadavers and models. We aimed to determine the resolution of the technique in the nose of living subjects. Silicone spheres of 3.0, 5.0, and 7.0 mm diameter were placed at two sites in the decongested and locally anaesthetised nasal cavities of 3 healthy adults. Acoustic rhinometry area-distance functions were obtained before and after insertion of the spheres, with further control data obtained after removal of the sphere from the nasal cavity. Six nasal cavities were studied in each test state on two separate occasions. The 3.0 mm sphere caused a statistically significant change in cavity volumes in only 17% of cases when placed in the middle meatus and in 8% at the nasal value (Mann-Whitney U-test; p < 0.05). The detection rates for the 5.0 mm sphere were 50% in the middle meatus and 50% at the nasal valve. When the control and test curves were compared by superimposition and the cross-sectional areas at the site of perturbations compared statistically (Mann-Whitney U-test) the detection rates in the middle meatus were: 33%-3.0 mm and 67%-5.0 mm sphere. The detection rate at the nasal valve region was 25%-3.0 mm sphere and 58%-5.0 mm. The 7.0 mm sphere was detected in 100% cases by volume changes, and 80% by area changes. Acoustic rhinometry can reliably detect changes of volume and area in the living nose resulting from the introduction of a 7 mm sphere into the nasal valve or middle meatal region in most cases. Smaller spheres are detected in only a fraction of cases. The resolution of the technique is therefore close to 7.0 mm (1.44 cm3). These findings are important when interpreting acoustic rhinometry data in monitoring patients with nasal pathology.
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Affiliation(s)
- E W Fisher
- Professorial Unit, Royal National Throat, Nose and Ear Hospital, London, UK
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Fisher EW, Moffat DA, Quinn SJ, Wareing MJ, Von Blumenthal H, Morris DP. Reduction in junior doctors' hours in an otolaryngology unit: effects on the 'out of hours' working patterns of all grades. Ann R Coll Surg Engl 1994; 76:232-5. [PMID: 7979091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
This study aimed to assess the effects of recent controls on juniors' duty hours (the 'New Deal') on the work performed by all grades of ENT medical staff 'out of hours'. For 100 days in 1993 the out of hours duties of all grades of doctor in the Otolaryngology Unit were monitored using daily logs. Three patterns of cover were run in parallel and subjected to comparison: Light: Senior House Officer (SHO)--Consultant (CON); Traditional: SHO-Intermediate (Registrar or Senior Registrar)--Consultant; Cross-cover--Pre-Registration House Officer (PRHO)--Intermediate-Consultant. The SHO 'out of hours' daily workload did not differ significantly between the traditional and light systems (median hours: 5.6 versus 5.0). There was an increase in working hours for the intermediate (registrar or senior registrar) grade of 84 per cent when the cross-cover system was in operation compared with the traditional system (median hours: 5.0 versus 2.8; p < 0.0001--Mann-Whitney U test). Consultant working hours increased by an average of 132 per cent as a result of removal of the intermediate tier (median hours: 1.7 versus 0.80; p < 0.0001). Reduction in on-call hours of junior staff resulted in a need for cross-cover and also in the frequent removal of an intermediate tier of staff. This has been shown to have a considerable effect on working patterns for intermediate and senior grades in an ENT unit of average size. Further reductions would be expected to have major effects on the working patterns of the consultant grade and considerably dilute the emergency experience of trainees.
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Affiliation(s)
- E W Fisher
- Department of Otolaryngology, Addenbrooke's Hospital, Cambridge
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Morris DP, Soute BA, Vermeer C, Stafford DW. Characterization of the purified vitamin K-dependent gamma-glutamyl carboxylase. J Biol Chem 1993; 268:8735-42. [PMID: 8473318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Vitamin K-dependent carboxylase, purified from bovine liver, has properties similar to those reported for the carboxylase activity present in crude, solubilized microsomes. The purified carboxylase was found to possess the vitamin K epoxidase activity, believed to be essential for vitamin K-dependent carboxylation, but did not contain vitamin K epoxide reductase activity. Kinetic studies of the carboxylase done under defined conditions were complicated by the non-Michaelis-Menten kinetic behavior observed for reactions with two of the enzymes substrates, FLEEL and vitamin K1 hydroquinone. Initial rate experiments with the substrate FLEEL demonstrated behavior consistent with substrate inhibition and gave half-maximal activity at 1 mM FLEEL. Experiments with the substrate vitamin K1 hydroquinone also displayed non-Michaelis-Menten kinetics, as maximal activity was reached prematurely in relation to behavior at lower concentrations. Half-maximal activity was observed at 35 microM vitamin K1 hydroquinone. Initial rate experiments with varying NaH14CO3 concentration displayed Michaelis-Menten kinetics and gave a Km(app) of 0.29 mM. At cosubstrate concentrations chosen to obtain near-maximal activity, initial rate studies with varying NaH14CO3 concentration indicated a kcat near 1.0 s-1. Removal of the fourth substrate, oxygen, resulted in the loss of more than 99% of carboxylase activity. The sulfhydryl reagent N-ethylmaleimide inhibited carboxylase irreversibly, as did the anticoagulant warfarin.
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Affiliation(s)
- D P Morris
- Department of Biology, University of North Carolina, Chapel Hill 27599-3280
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Abstract
Vitamin K-dependent carboxylase catalyzes the modification of specific glutamic acids to gamma-carboxyglutamic acid in several blood-coagulation proteins. This modification is required for the blood-clotting activity of these proteins and has thus been the subject of intense investigation. We have now identified the bovine vitamin K-dependent carboxylase and purified it to near homogeneity by an affinity procedure that uses the 59-amino acid peptide FIXQ/S (residues -18 to 41 of factor IX with mutations Arg----Gln at residue -4 and Arg----Ser at residue -1). The carboxylase as purified has a molecular weight of 94,000. It is also the major protein that can be cross-linked to iodinated FIXQ/S and is the only protein whose cross-linking is prevented by a synthetic factor IX propeptide. The degree of purification is about 7000-fold with reference to ammonium sulfate-fractionated microsomal protein from liver.
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Affiliation(s)
- S M Wu
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599-3280
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Shanahan MF, Morris DP, Edwards BM. [3H]forskolin. Direct photoaffinity labeling of the erythrocyte D-glucose transporter. J Biol Chem 1987; 262:5978-84. [PMID: 3106349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Irradiation of erythrocyte ghosts in the presence of [3H]forskolin resulted in a concentration-dependent, covalent incorporation of radiolabel into several of the major membrane protein bands. Most of the incorporation occurred in four regions of the gel. Peak 1 (216 kDa) was a sharp peak near the top of the gel in the region corresponding to spectrin. Peak 2 appeared to be associated with band 3 (89 kDa), while a third peak occurred around the position of band 4.2 (76 kDa). The fourth region of labeling was a broad area between 43-75 kDa which corresponds to the region of the glucose transporter. Forskolin labeling of this region was inhibited by cytochalasin B and D-glucose, but not L-glucose. Extraction of extrinsic membrane proteins resulted in a loss of radiolabeled protein from the 216- and 76-kDa regions. Treatment of membranes labeled with either cytochalasin B or forskolin with endo-beta-galactosidase resulted in identical shifts of the 43 to 75-kDa peaks to 42 kDa. Similarly, trypsinization of membranes photolabeled with either cytochalasin B or forskolin resulted in the generation of a 17-kDa radiolabeled fragment in both cases. Photoincorporation of [3H]cytochalasin B into the glucose transporter was blocked in a concentration-dependent manner by unlabeled forskolin.
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Morris DP. Designing a quality thermodilution catheter. Med Electron 1982; 13:80-2. [PMID: 10260259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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