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Coulie B, Matsuura B, Dong M, Hadac EM, Pinon DI, Feighner SD, Howard AD, Miller LJ. Identification of peptide ligand-binding domains within the human motilin receptor using photoaffinity labeling. J Biol Chem 2001; 276:35518-22. [PMID: 11461914 DOI: 10.1074/jbc.m104489200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cDNA encoding the human motilin receptor was recently cloned and found to represent a G protein-coupled receptor that is structurally related to the growth hormone secretagogue receptors. Together, these represent a new Class I receptor family. Our aim in the present work is to gain insight into the molecular basis of binding of motilin to its receptor using photoaffinity labeling. To achieve this, we developed a Chinese hamster ovary cell line that overexpressed functional motilin receptor (CHO-MtlR; 175,000 sites per cell, with K(i) = 2.3 +/- 0.4 nm motilin and EC(50) = 0.3 +/- 0.1 nm motilin) and a radioiodinatable peptide analogue of human motilin that incorporated a photolabile p-benzoyl-l-phenylalanine (Bpa) residue into its pharmacophoric domain. This probe, [Bpa(1),Ile(13)]motilin, was a full agonist at the motilin receptor that increased intracellular calcium in a concentration-dependent manner (EC(50) = 1.5 +/- 0.4 nm). This photolabile ligand bound specifically and with high affinity to the motilin receptor (K(i) = 12.4 +/- 1.0 nm), and covalently labeled that molecule within its M(r) = 45,000 deglycosylated core. Cyanogen bromide cleavage demonstrated its covalent attachment to fragments of the receptor having apparent M(r) = 6,000 and M(r) = 31,000. These were demonstrated to represent fragments that included both the first and the large second extracellular loop domains, with the latter representing a unique structural feature of this receptor. The spatial approximation of the pharmacophoric domain of motilin with these receptor domains support their functional importance as well.
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Nardone G, Holicky EL, Uhl JR, Sabatino L, Staibano S, Rocco A, Colantuoni V, Manzo BA, Romano M, Budillon G, Cockerill FR, Miller LJ. In vivo and in vitro studies of cytosolic phospholipase A2 expression in Helicobacter pylori infection. Infect Immun 2001; 69:5857-63. [PMID: 11500464 PMCID: PMC98704 DOI: 10.1128/iai.69.9.5857-5863.2001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2000] [Accepted: 06/11/2001] [Indexed: 02/07/2023] Open
Abstract
Modifications of mucosal phospholipids have been detected in samples from patients with Helicobacter pylori-positive gastritis. These alterations appear secondary to increased phospholipase A2 activity (PLA2). The cytosolic form of this enzyme (cPLA2), normally involved in cellular signaling and growth, has been implicated in cancer pathogenesis. The aim of this study was to investigate cPLA2 expression and PLA2 activity in the gastric mucosae of patients with and without H. pylori infection. In gastric biopsies from 10 H. pylori-positive patients, cPLA2 levels, levels of mRNA as determined by reverse transcriptase PCR, levels of protein as determined by immunohistochemistry, and total PLA2 activity were higher than in 10 H. pylori-negative gastritis patients. To clarify whether H. pylori had a direct effect on the cellular expression of cPLA2, we studied cPLA2 expression in vitro with different human epithelial cell lines, one from a patient with larynx carcinoma (i.e., HEp-2 cells) and two from patients with gastric adenocarcinoma (i.e., AGS and MKN 28 cells), incubated with different H. pylori strains. The levels of cPLA2, mRNA, and protein expression were unchanged in Hep-2 cells independently of cellular adhesion or invasion of the bacteria. Moreover, no change in cPLA2 protein expression was observed in AGS or MKN 28 cells treated with wild-type H. pylori. In conclusion, our study shows increased cPLA2 expression and PLA2 activity in the gastric mucosae of patients with H. pylori infection and no change in epithelial cell lines exposed to H. pylori.
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Ding XQ, Ding WQ, Miller LJ. Receptor biology and signal transduction. Curr Opin Gastroenterol 2001; 17:410-5. [PMID: 17031193 DOI: 10.1097/00001574-200109000-00002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
This year has witnessed substantial advances in receptor biology and signal transduction that are relevant to the function and regulation of the healthy pancreas and to the pathogenesis and potential therapy of pancreatitis and pancreatic carcinoma. There has been an expansion in the cast of pancreatic regulatory molecules, now including protease-activated receptors, chemokines, and chemokine receptors. There have been new insights into the cellular distribution and signaling initiated at the classic pancreatic receptors. There have also been dramatic advances in insights into the structure of G protein-coupled receptors, with the first solution of a crystal structure of a member of this superfamily, and into the molecular basis of ligand binding and activation of these important molecules. This will clearly improve the opportunities for the rational design and refinement of receptor-active drugs. In addition to these fundamental advances, there has been renewed attention to the expression, function, and regulation of receptors and signaling pathways in pancreatic cells present in the setting of pancreatitis and pancreatic carcinoma. It is hoped that this will contribute toward earlier diagnosis, more successful therapy, and new chemopreventive strategies for these illnesses.
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Chari ST, Klee GG, Miller LJ, Raimondo M, DiMagno EP. Islet amyloid polypeptide is not a satisfactory marker for detecting pancreatic cancer. Gastroenterology 2001; 121:640-5. [PMID: 11522748 DOI: 10.1053/gast.2001.27210] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
BACKGROUND & AIMS Islet amyloid polypeptide (IAPP) levels are elevated in pancreatic cancer and may be a useful marker of pancreatic cancer-associated diabetes. The aim of this study was to compare the sensitivity and specificity for pancreatic cancer of IAPP with that of CA19-9, examine clinical characteristics of diabetes in pancreatic cancer, and define the relationship of IAPP to diabetes of pancreatic cancer. METHODS Fasting serum glucose, IAPP, and CA 19-9 were measured in 130 subjects with pancreatic cancer, 250 subjects with other pancreatic and peripancreatic diseases, and 116 controls. In pancreatic cancer patients, we noted tumor stage and the presence and duration of diabetes. RESULTS IAPP was markedly elevated in pancreatic cancer, especially in patients with diabetes. However, the sensitivity of IAPP for pancreatic cancer was less than that of CA 19-9 (40% vs. 75%; P < 0.001). Diabetes was present in 46% of pancreatic cancers and 55% of resectable tumors. In pancreatic cancer with diabetes, the sensitivity of IAPP was only 50%. In resectable cancer it was 27%. CONCLUSIONS IAPP is elevated in pancreatic cancer but is not sensitive enough to replace or complement existing tests. Diabetes occurs early and frequently in pancreatic cancer. Development of a sensitive and specific marker for pancreatic-associated diabetes might lead to diagnosis of resectable pancreatic cancer.
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Holicky EL, Hadac EM, Ding XQ, Miller LJ. Molecular characterization and organ distribution of type A and B cholecystokinin receptors in cynomolgus monkey. Am J Physiol Gastrointest Liver Physiol 2001; 281:G507-14. [PMID: 11447031 DOI: 10.1152/ajpgi.2001.281.2.g507] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Differences in the molecular structure or organ distribution of receptors can limit the usefulness of a given species for drug studies. In this work, we have studied cholecystokinin (CCK) receptors in cynomolgus monkey, an animal model useful for preclinical testing. The type A CCK receptor cDNA was cloned and predicted to encode a 428 amino acid peptide that was 98% identical to the human receptor. Only 2 of the 10 residues that were distinct from the human receptor were not present in other cloned CCK receptor species. A Chinese hamster ovary cell line that stably expressed this receptor was developed. The cynomolgus receptor expressed in this environment was functionally indistinguishable from the human receptor, binding CCK with high affinity [inhibition constant (K(I)) = 1.8 +/- 0.5 nM] and exhibiting a potent intracellular calcium signaling response to this hormone (EC(50) = 6.6 +/- 2.1 pM). Like the human type A CCK receptor, this receptor was expressed prominently in monkey gallbladder and stomach and was expressed in low levels in brain and pancreas. The type B CCK receptor cDNA was cloned from stomach and brain (450 residue receptor that is 96% identical to the human receptor), where it was highly expressed yet was undetectable in gallbladder or pancreas. This work confirms the relevance of the cynomolgus species for preclinical testing of drugs acting on the type A CCK receptor.
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Ding XQ, Miller LJ. Characterization of the type A cholecystokinin receptor hormone-binding domain: use of contrasting and complementary methodologies. Peptides 2001; 22:1223-8. [PMID: 11457514 DOI: 10.1016/s0196-9781(01)00445-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Insights into the molecular basis of binding of the peptide hormone, cholecystokinin, to its G protein-coupled receptor is of substantial interest and may contribute to the successful production and refinement of receptor-active drugs. A number of methodological approaches provide complementary data to contribute to these insights. These include receptor mutagenesis, ligand structure-activity data, conformational analysis of ligand and receptor fragments, and photoaffinity labeling. In this work, we compare and contrast each of these methods and provide our current view of the cumulative impact of the current data on molecular conformational models of the agonist-occupied type A cholecystokinin receptor. These support the key roles played by extracellular loop and tail regions of this receptor for binding its natural peptide ligand.
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Miller LJ, Haven CP, McCollum SG, Lee AM, Kamman MR, Baumann DK, Anderson ME, Buderer MC. The International Space Station human life sciences experiment implementation process. ACTA ASTRONAUTICA 2001; 49:477-482. [PMID: 11669134 DOI: 10.1016/s0094-5765(01)00130-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The selection, definition, and development phases of a Life Sciences flight research experiment has been consistent throughout the past decade. The implementation process, however, has changed significantly within the past two years. This change is driven primarily by the shift from highly integrated, dedicated research missions on platforms with well defined processes to self contained experiments with stand alone operations on platforms which are being concurrently designed. For experiments manifested on the International Space Station (ISS) and/or on short duration missions, the more modular, streamlined, and independent the individual experiment is, the more likely it is to be successfully implemented before the ISS assembly is completed. During the assembly phase of the ISS, science operations are lower in priority than the construction of the station. After the station has been completed, it is expected that more resources will be available to perform research. The complexity of implementing investigations increases with the logistics needed to perform the experiment. Examples of logistics issues include- hardware unique to the experiment; large up and down mass and volume needs; access to crew and hardware during the ascent or descent phases; maintenance of hardware and supplies with a limited shelf life,- baseline data collection schedules with lengthy sessions or sessions close to the launch or landing; onboard stowage availability, particularly cold stowage; and extensive training where highly proficient skills must be maintained. As the ISS processes become better defined, experiment implementation will meet new challenges due to distributed management, on-orbit resource sharing, and adjustments to crew availability pre- and post-increment.
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Jiang SW, Dong M, Trujillo MA, Miller LJ, Eberhardt NL. DNA binding of TEA/ATTS domain factors is regulated by protein kinase C phosphorylation in human choriocarcinoma cells. J Biol Chem 2001; 276:23464-70. [PMID: 11313339 DOI: 10.1074/jbc.m010934200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transcription enhancer factor 1 (TEF-1) controls the expression of a diverse set of genes. Previous studies implicated protein kinase C (PKC)-mediated signal transduction in modulating TEF function. We demonstrate that in human choriocarcinoma BeWo cells, the PKC activator 12-O-tetradecanoyl phorbol 13-acetate and PKC inhibitor bisindolylmaleimide reciprocally down- and up-regulate, respectively, TEF-mediated GGAATG core enhancer activity. In vitro TEF-1 phosphorylation with several PKC isozymes and phosphoamino acid analysis confirmed that TEF-1 is a potential PKC substrate. TEF-1.DNA complexes formed by BeWo nuclear extracts are supershifted by phosphoserine- and phosphothreonine- but not phosphotyrosine-specific antibodies, indicating that TEF-1 is phosphorylated in vivo at serine and threonine residues. The TEF-1 phosphorylation domain was localized to the third alpha-helix of the DNA binding domain and adjacent hinge region by phosphopeptide analysis. TEF-1 phosphorylation significantly reduced its DNA binding activity both in vitro and in vivo, providing a possible mechanism for the inhibitory action of PKC. Finally, BeWo cells contained abundant levels of gamma and delta PKC isoforms, and their overexpression resulted in even greater inhibition of GGAATG core enhancer activity after 12-O-tetradecanoyl phorbol 13-acetate treatment. These data strongly suggest that PKC-mediated phosphorylation is a key factor controlling TEF function.
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Mangeot SD, Miller LJ, McIntosh DN, McGrath-Clarke J, Simon J, Hagerman RJ, Goldson E. Sensory modulation dysfunction in children with attention-deficit-hyperactivity disorder. Dev Med Child Neurol 2001; 43:399-406. [PMID: 11409829 DOI: 10.1017/s0012162201000743] [Citation(s) in RCA: 183] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This study investigates the presence of sensory modulation dysfunction (SMD) among children with attention-deficit-hyperactivity disorder (ADHD). Twenty-six children with ADHD (mean age 8.3 years, 18 males, 8 females), and 30 typically developing children (mean age 8.2 years, 21 males, 9 females) were tested using a laboratory procedure that gauges responses to repeated sensory stimulation by measuring electrodermal reactivity (EDR). Parental report measures of limitations in sensory, emotional, and attentional dimensions were administered using the Short Sensory Profile, the Leiter International Performance Scale-Revised, Parent Rating subscales, and the Child Behavior Checklist (CBCL). Compared to the typical sample, the children with ADHD displayed greater abnormalities in sensory modulation on both physiological and parent-report measures. The children with ADHD also displayed more variability in responses. Within the group with ADHD, levels of SMD were highly correlated with measures of psychopathology on the CBCL. Implications of findings relate to the importance of considering sensory processing abilities in a subgroup of children with ADHD.
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Mullick M, Miller LJ, Jacobsen T. Insight into mental illness and child maltreatment risk among mothers with major psychiatric disorders. Psychiatr Serv 2001; 52:488-92. [PMID: 11274495 DOI: 10.1176/appi.ps.52.4.488] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
OBJECTIVES This study examined the relationship between insight into mental illness and current child maltreatment risk among mothers who had a major psychiatric disorder and who had lost custody of a child because of abuse, neglect, or having placed the child at risk of harm. Specifically, a measure of insight was examined in relation to systematically observed parenting behaviors known to be correlated with past child maltreatment and in relation to a comprehensive clinical determination of risk. METHODS Forty-four mothers who had a major psychiatric disorder were independently rated for their insight into their illness, the quality of mother-child interaction, and the overall clinical risk of maltreatment. RESULTS Better insight into mental illness was associated with more sensitive mothering behavior and with lower assessed clinical risk of maltreatment. The association remained when mothers with current psychotic symptoms were excluded from the analyses. Better insight did not appear to be associated with past psychotic symptoms, maternal psychiatric diagnosis, or the mother's level of education. CONCLUSIONS Insight into mental illness may function as a protective factor that influences the risk of child maltreatment in mothers with mental illness. Measures of insight could be usefully incorporated into comprehensive parenting assessments for mothers with psychiatric disorders.
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Abstract
BACKGROUND Controversy persists regarding the reasons for persistent subjective complaints after mild traumatic head injury (THI). STATEMENT OF PURPOSE To evaluate the influence of injury severity, psychological factors, and financial contingencies on symptomatology after THI. METHODS Subjective complaints about cognitive, emotional, and somatic symptoms, as assessed by a standardized self-report inventory (Minnesota Multiphasic Personality Inventory-2; MMPI-2) were evaluated in 150 patients with THI. RESULTS Individuals with mild THI demonstrated paradoxically greater symptomatology on the MMPI-2 than patients with moderate-to-severe THI. Furthermore, specific actuarial criteria for possible symptom magnification (Fake Bad Scale) were met about twice as often in patients with mild THI who were seeking financial compensation for alleged acquired dysfunction than in patients with mild THI without such external contingencies. CONCLUSION The evaluation of persistent subjective complaints after THI should consider injury severity in concert with psychological and financial/motivational factors. Great caution should be taken in attributing persistent symptomatology after mild THI to cerebral dysfunction.
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Miller LJ. Gabapentin for treatment of behavioral and psychological symptoms of dementia. Ann Pharmacother 2001; 35:427-31. [PMID: 11302405 DOI: 10.1345/aph.10217] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
OBJECTIVE To report the use of gabapentin in the treatment of behavioral and psychological symptoms of dementia (BPSD) and to review the available literature relating to the use of gabapentin in this population. CASE SUMMARY A 62-year-old white man was admitted to the hospital due to a worsening state of confusion, anxiety, depressed mood, insomnia, and verbal and physical aggressiveness toward his wife. He had a past medical history significant for vascular dementia. He had been intolerant of or had failed to respond to numerous antidepressants, benzodiazepines, and neuroleptics. The addition of gabapentin to the patient's medication regimen resulted in reduced agitation, sexual inappropriateness, and lability. He was discharged to his home on a dose of gabapentin 300 mg three times daily. DATA SOURCES A MEDLINE search (1966-August 2000) was performed to identify case reports and clinical trials discussing the efficacy of gabapentin in the treatment of BPSD. DISCUSSION Gabapentin, like other anticonvulsants, has been used with success in several psychiatric illnesses. Available literature indicates that the drug may have some efficacy in the treatment of BPSD. It has a favorable adverse effect profile in the elderly, which makes it an attractive altemative to standard therapies, including benzodiazepines and neuroleptics. Optimal dosing remains unclear. CONCLUSIONS This case suggests that gabapentin is a reasonable alternative therapy for patients whose behavioral symptoms do not respond to conventional agents.
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Dong M, Wang Y, Miller LJ. Dual contacts between peptide agonist ligands and the secretin receptor directly established by photoaffinity labeling. Ann N Y Acad Sci 2001; 921:381-6. [PMID: 11193860 DOI: 10.1111/j.1749-6632.2000.tb07000.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Structural analysis of secretin in solution has demonstrated extended helical domains within both amino- and carboxyl-terminal halves, with a possible turn in between. However, the conformation of this peptide as it resides in its binding site within the receptor has not been established. In the work reported here, we performed affinity labeling of the secretin receptor with radioiodinated secretin analogues having photolabile benzoyl-phenylalanine residues positioned in each half of the peptide. The probes had sites of covalent attachment in positions 6 and 22, and have been recently synthesized and characterized to represent high affinity agonist ligands. Both covalently labeled the secretin receptor in a saturable, specific, and efficient manner. After purification of the labeled receptor, we used a series of chemical and enzymatic cleavage techniques to define the domain of labeling. We complemented this by receptor mutagenesis, followed by additional cleavage and Edman degradation sequencing to refine our insights into the labeled residues. This has allowed us to demonstrate that sites of attachment were both within the extracellular aminoterminal domain of the receptor. Of particular interest, both probes labeled residues within the amino-terminal thirty residues at the distal end of the receptor. It will be particularly interesting to use these molecular approximations to model the binding domain of this important receptor.
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Ding XQ, Dolu V, Hadac EM, Holicky EL, Pinon DI, Lybrand TP, Miller LJ. Refinement of the structure of the ligand-occupied cholecystokinin receptor using a photolabile amino-terminal probe. J Biol Chem 2001; 276:4236-44. [PMID: 11050076 DOI: 10.1074/jbc.m003798200] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Affinity labeling is a powerful tool to establish spatial approximations between photolabile residues within a ligand and its receptor. Here, we have utilized a cholecystokinin (CCK) analogue with a photolabile benzoylphenylalanine (Bpa) sited in position 24, adjacent to the pharmacophoric domain of this hormone (positions 27-33). This probe was a fully efficacious agonist that bound to the CCK receptor saturably and with high affinity (K(i) = 8.9 +/- 1.1 nm). It covalently labeled the CCK receptor either within the amino terminus (between Asn(10) and Lys(37)) or within the third extracellular loop (Glu(345)), as demonstrated by proteolytic peptide mapping, deglycosylation, micropurification, and Edman degradation sequencing. Truncation of the receptor to eliminate residues 1-30 had no detrimental effect on CCK binding, stimulated signaling, or affinity labeling through a residue within the pharmacophore (Bpa(29)) but resulted in elimination of the covalent attachment of the Bpa(24) probe to the receptor. Thus, the distal amino terminus of the CCK receptor resides above the docked ligand, compressing the portion of the peptide extending beyond its pharmacophore toward the receptor core. Exposure of wild type and truncated receptor constructs to extracellular trypsin damaged the truncated construct but not the wild type receptor, suggesting that this domain also may play a protective role. Use of these additional insights into molecular approximations provided key constraints for molecular modeling of the peptide-receptor complex, supporting the counterclockwise organization of the transmembrane helical domains.
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Tietz PS, Hadac EM, Miller LJ, LaRusso NF. Upregulation of secretin receptors on cholangiocytes after bile duct ligation. REGULATORY PEPTIDES 2001; 97:1-6. [PMID: 11166400 DOI: 10.1016/s0167-0115(00)00109-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Secretin not only increases ductular bile secretion in vivo in rats after bile duct ligation (BDL) [1], but also increases cAMP levels and stimulates exocytosis in isolated cholangiocytes [2]. Although we have previously reported that secretin receptor mRNA was upregulated in cholangiocytes after BDL [3], the cholangiocyte secretin receptor has not been functionally characterized or quantified after BDL. In this work, we used a novel, photolabile and biologically active analogue of secretin to quantify and characterize secretin receptors on cholangiocytes isolated from normal and BDL rats. The cholangiocyte secretin receptor bound radioligand with high affinity and in a rapid, reversible, and temperature-dependent manner. While receptors on cholangiocytes from normal and BDL rats were functionally and biochemically identical, receptor density on cholangiocytes was increased 5-fold following BDL. The combination of increased cell number with increased functional secretin receptors per cell is due to the fact that cholangiocyte hyperplasia represents a reactive response to a cholestatic condition and this effort on the part of the organism to maintain bile secretion, explains the increased hormone-responsive choleresis observed after BDL and may reflect an adaptive response of the organism to cholestasis.
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Ding XQ, Rao RV, Kuntz SM, Holicky EL, Miller LJ. Impaired resensitization and recycling of the cholecystokinin receptor by co-expression of its second intracellular loop. Mol Pharmacol 2000; 58:1424-33. [PMID: 11093782 DOI: 10.1124/mol.58.6.1424] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Intermolecular interaction represents an important theme in regulation of intracellular trafficking of organelles that can be interrupted by competitive overexpression of a relevant molecular domain. We attempted to identify the functional importance of intracellular domains of the cholecystokinin (CCK) receptor by their over-expression in receptor-bearing Chinese hamster ovary (CHO-CCKR) cell lines. Although clathrin-dependent endocytosis and recycling of this receptor are well-established (J Cell Biol 128:1029-1042, 1995), any influence of distinct receptor domains is not understood. In this work, constructs representing each of the intracellular domains of the CCK receptor were coexpressed with wild-type receptor, and stable clonal cell lines were selected. Each was characterized for ligand binding and agonist-stimulated biological activity (inositol 1,4,5-trisphosphate generation), desensitization, resensitization, receptor internalization, and recycling. Each cell line expressed normal CCK radioligand binding, signaling, internalization, and desensitization. Three independent cell lines that coexpressed the 25-residue second intracellular loop domain exhibited deficient resensitization. In morphological assessment of receptor trafficking, this construct was also shown to interfere with receptor recycling to the plasma membrane. As a control, recycling of an unrelated G protein-coupled receptor was demonstrated to occur normally in this cell line. These observations suggest that rather than representing passive cargo within an endosome, a receptor can influence its own trafficking within the cell.
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Rao RV, Holicky EL, Kuntz SM, Miller LJ. CCK receptor phosphorylation exposes regulatory domains affecting phosphorylation and receptor trafficking. Am J Physiol Cell Physiol 2000; 279:C1986-92. [PMID: 11078715 DOI: 10.1152/ajpcell.2000.279.6.c1986] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Agonist-stimulated phosphorylation of guanine nucleotide-binding protein (G protein)-coupled receptors has been recognized as an important mechanism for desensitization by interfering with coupling of the activated receptor with its G protein. We recently described a mutant of the CCK receptor that modified two of five key sites of phosphorylation (S260,264A) and eliminated agonist-stimulated receptor phosphorylation, despite normal ligand binding and signaling (20). As expected, this nonphosphorylated mutant had impaired rapid desensitization but was ultimately able to be desensitized by normal receptor internalization. Here we demonstrate that this mutant receptor is also defective in resensitization, with abnormal recycling to the cell surface. To explore this, another receptor mutant was prepared, replacing the same serines with aspartates to mimic the charge of serine-phosphate (S260,264D). This mutant was expressed in a Chinese hamster ovary cell line and shown to bind CCK normally. It had accelerated kinetics of signaling and desensitization and was phosphorylated in response to agonist occupation, with all other normal sites of phosphorylation modified. It was internalized like wild-type receptors and was resensitized and trafficked normally. This provides evidence for an additional important function for phosphorylation of G protein-coupled receptors. Phosphorylation may induce a conformational change in the receptor to expose other potential sites of phosphorylation and to expose domains involved in the targeting and trafficking of endosomes. The hierarchical phosphorylation of these sites may play a key role in receptor regulation.
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Asmann YW, Dong M, Ganguli S, Hadac EM, Miller LJ. Structural insights into the amino-terminus of the secretin receptor: I. Status of cysteine and cystine residues. Mol Pharmacol 2000; 58:911-9. [PMID: 11040037 DOI: 10.1124/mol.58.5.911] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The secretin receptor is prototypic of the class II family of G protein-coupled receptors, with a long extracellular amino-terminal domain containing six highly conserved Cys residues and one Cys residue (Cys(11)) that is present only in the most closely related family members. This domain is critical for function, with some component Cys residues believed to be involved in key disulfide bonds, although these have never been directly demonstrated. Here, we examine the functional importance of each of these residues and determine their involvement in disulfide bonds. Secretin binding was markedly diminished after treating cells with cell-impermeant reducing reagents, supporting the presence of important extracellular disulfide bonds. To determine whether the amino-terminal domain was covalently attached to the receptor body by disulfide linkage, a strategy was implemented that involved introduction of an acid-labile Asp-Pro sequence to enable specific cleavage at the boundary of these domains. Under nonreducing conditions, the amino terminus was released from the receptor body, supporting the absence of covalent association between these domains. Quantitative [(14)C]iodoacetamide incorporation into the isolated amino-terminal domain of the receptor in the absence and presence of chemical reduction established the ratio of free to total Cys residues as 1:7, consistent with three disulfide bonds. Mutagenesis of each of the amino-terminal Cys residues to Ala was tolerated only for Cys(11), suggesting that these bonds linked the conserved Cys residues. This was further supported by treatment of intact cells expressing wild-type or C11A mutant secretin receptor with a cell-impermeant sulfhydryl-reactive reagent. Thus, the functionally important amino terminus of the secretin receptor represents a structurally independent, highly folded, and disulfide-bonded domain, with a pattern that is likely critical and conserved throughout this receptor family.
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Park CG, Ganguli SC, Pinon DI, Hadac EM, Miller LJ. Cross-chimeric analysis of selectivity of secretin and VPAC(1) receptor activation. J Pharmacol Exp Ther 2000; 295:682-8. [PMID: 11046106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023] Open
Abstract
Agonist action at receptors is highly specific, affected by the structure of both ligand and receptor. Chimeric constructs of structurally related receptors and/or ligands that have biological differences provide an opportunity to correlate a specific structural domain with function. In this work, we have used a cross-chimeric approach to explore the structural basis for rat secretin and vasoactive intestinal polypeptide action at their closely related secretin and VPAC(1) receptors, belonging to class II of the G protein-coupled receptor superfamily. Multiple domains of both ligands and receptors contributed toward their selectivity, with differing combinations of such domains able to support high-potency interactions. The amino-terminal 15 residues of secretin were most critical for potent stimulation of secretin receptors, whereas either the amino- or carboxyl-terminal halves of vasoactive intestinal polypeptide, when complemented by Lys(15), provided potent stimulation of the VPAC(1) receptor. The amino terminus of the VPAC(1) receptor was most critical for potent response to vasoactive intestinal polypeptide, whereas the amino terminus of the secretin receptor was important, but not adequate, requiring the complementation of an extracellular loop domain for potent response to secretin. Differences in the distribution of these determinants within these receptors provided an opportunity to produce a more "universal" receptor that contained the first extracellular loop of the secretin receptor and the remainder of the VPAC(1) receptor. This cross-chimeric approach should be applied to other members of this receptor family to test the emerging themes and to expand these insights as broadly as possible.
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Ferrer FA, Pantschenko AG, Miller LJ, Anderson K, Grunnet M, McKenna PH, Kreutzer D. Angiogenesis and neuroblastomas: interleukin-8 and interleukin-8 receptor expression in human neuroblastoma. J Urol 2000. [PMID: 10958731 DOI: 10.1016/s0022-5347(05)67240-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE Studies have demonstrated that the pro-angiogenic cytokine interleukin-8 (IL-8) and the IL-8 receptors likely have a role in the growth and metastasis of various solid tumors. We hypothesized that in vivo neuroblastoma expresses IL-8 and the IL-8 receptors A and B, and that factors known to regulate IL-8 expression are present and active in the neuroblastoma microenvironment. MATERIALS AND METHODS To confirm the presence of IL-8/IL-8 receptors in neuroblastoma, immunohistochemical analysis for IL-8 and its receptors was performed on 10 archival specimens, including benign adrenal and well to poorly differentiated neuroblastoma samples. Immunohistochemical analysis was also performed for interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha. Cultured neuroblastoma cells SK-N-MC and SK-N-SH were stimulated with 10 ng./ml. IL-1beta or tumor necrosis factor-alpha and control media (15 each). Cell culture supernatants were analyzed with enzyme-linked immunosorbant assay for IL-8 levels at 24 and 48 hours. RESULTS Minimal expression of IL-8 was noted in benign adrenal tissue but expression for IL-8 was present in all neuroblastoma specimens. Microvessel staining was present in 30% of the specimens. All tumor specimens expressed IL-8 receptor B, and both receptors were expressed in the tumor microvasculature. Immunohistochemical analysis confirmed the presence of IL-1beta and tumor necrosis factor in the neuroblastoma microenvironment. In vitro studies demonstrated that SK-N-MC and SK-N-SH cells express low levels of IL-8 under normal conditions and that IL-1beta and tumor necrosis factor-alpha significantly increased expression of IL-8 at 24 and 48 hours. CONCLUSIONS Our results indicate that IL-8 and its receptors are expressed in neuroblastoma tumor specimens. In addition, the fact that IL-1beta and tumor necrosis factor-alpha are expressed in the neuroblastoma microenvironment combined with our in vitro results suggests that these cytokines may be involved in in vivo regulation of IL-8 in human neuroblastoma. Understanding the angiogenic factors and regulatory cascade promoting angiogensis in neuroblastoma may lead to the development of effective anti-angiogenic strategies.
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Ferrer FA, Pantschenko AG, Miller LJ, Anderson K, Grunnet M, McKenna PH, Kreutzer D. Angiogenesis and neuroblastomas: interleukin-8 and interleukin-8 receptor expression in human neuroblastoma. J Urol 2000; 164:1016-20. [PMID: 10958731 DOI: 10.1097/00005392-200009020-00024] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE Studies have demonstrated that the pro-angiogenic cytokine interleukin-8 (IL-8) and the IL-8 receptors likely have a role in the growth and metastasis of various solid tumors. We hypothesized that in vivo neuroblastoma expresses IL-8 and the IL-8 receptors A and B, and that factors known to regulate IL-8 expression are present and active in the neuroblastoma microenvironment. MATERIALS AND METHODS To confirm the presence of IL-8/IL-8 receptors in neuroblastoma, immunohistochemical analysis for IL-8 and its receptors was performed on 10 archival specimens, including benign adrenal and well to poorly differentiated neuroblastoma samples. Immunohistochemical analysis was also performed for interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha. Cultured neuroblastoma cells SK-N-MC and SK-N-SH were stimulated with 10 ng./ml. IL-1beta or tumor necrosis factor-alpha and control media (15 each). Cell culture supernatants were analyzed with enzyme-linked immunosorbant assay for IL-8 levels at 24 and 48 hours. RESULTS Minimal expression of IL-8 was noted in benign adrenal tissue but expression for IL-8 was present in all neuroblastoma specimens. Microvessel staining was present in 30% of the specimens. All tumor specimens expressed IL-8 receptor B, and both receptors were expressed in the tumor microvasculature. Immunohistochemical analysis confirmed the presence of IL-1beta and tumor necrosis factor in the neuroblastoma microenvironment. In vitro studies demonstrated that SK-N-MC and SK-N-SH cells express low levels of IL-8 under normal conditions and that IL-1beta and tumor necrosis factor-alpha significantly increased expression of IL-8 at 24 and 48 hours. CONCLUSIONS Our results indicate that IL-8 and its receptors are expressed in neuroblastoma tumor specimens. In addition, the fact that IL-1beta and tumor necrosis factor-alpha are expressed in the neuroblastoma microenvironment combined with our in vitro results suggests that these cytokines may be involved in in vivo regulation of IL-8 in human neuroblastoma. Understanding the angiogenic factors and regulatory cascade promoting angiogensis in neuroblastoma may lead to the development of effective anti-angiogenic strategies.
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Dong M, Asmann YW, Zang M, Pinon DI, Miller LJ. Identification of two pairs of spatially approximated residues within the carboxyl terminus of secretin and its receptor. J Biol Chem 2000; 275:26032-9. [PMID: 10859300 DOI: 10.1074/jbc.m000612200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The carboxyl-terminal domains of secretin family peptides have been shown to contain key determinants for high affinity binding to their receptors. In this work, we have examined the interaction between carboxyl-terminal residues within secretin and the prototypic secretin receptor. We previously utilized photoaffinity labeling to demonstrate spatial approximation between secretin residue 22 and the receptor domain that includes the first 30 residues of the amino terminus (Dong, M., Wang, Y., Pinon, D. I., Hadac, E. M., and Miller, L. J. (1999) J. Biol. Chem. 274, 903-909). Here, we further refined the site of labeling with the p-benzoyl-phenylalanine (Bpa(22)) probe to receptor residue Leu(17) using progressive cleavage of wild type and mutant secretin receptors (V13M and V16M) and sequence analysis. We also developed a new probe incorporating a photolabile Bpa at position 26 of secretin, closer to its carboxyl terminus. This analogue was also a potent agonist (EC(50) = 72 +/- 6 pm) and bound to the secretin receptor specifically and with high affinity (K(i) = 10.3 +/- 2.4 nm). It covalently labeled the secretin receptor at a single site saturably and specifically. This was localized to the segment between residues Gly(34) and Ala(41) using chemical and enzymatic cleavage of labeled wild type and A41M mutant receptor constructs and immunoprecipitation of epitope-tagged receptor fragments. Radiochemical sequencing identified the site of covalent attachment as residue Leu(36). These new insights, along with our recent report of contact between residue 6 within the amino-terminal half of secretin and this same amino-terminal region of this receptor (Dong, M., Wang, Y., Hadac, E. M., Pinon, D. I., Holicky, E. L., and Miller, L. J. (1999) J. Biol. Chem. 274, 19161-19167), support a key role for this region, making the molecular details of this interaction of major interest.
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Miller LJ, Kurtzman SH, Anderson K, Wang Y, Stankus M, Renna M, Lindquist R, Barrows G, Kreutzer DL. Interleukin-1 family expression in human breast cancer: interleukin-1 receptor antagonist. Cancer Invest 2000; 18:293-302. [PMID: 10808364 DOI: 10.3109/07357900009012171] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We hypothesize that interleukin-1 alpha, beta, and receptor antagonist (IL-1 alpha, IL-1 beta, and IL-1 ra, respectively) are present and tumor cell associated in human breast cancer (HBC). We believe the levels of these cytokines in breast tumor homogenates relate to other known prognosticators of patient survival (i.e., estrogen receptor [ER] status). Our results demonstrated that, immunohistochemically, tumor cells express IL-1 alpha, IL-1 beta, and IL-1 ra in most specimens tested. In breast tissue homogenates, IL-1 alpha levels correlated inversely with ER levels (p < 0.06), whereas IL-1 ra levels correlated directly with both ER levels (p < 0.009) and IL-1 beta levels (p < 0.06). When analyzing cytokine levels for the ER (-) versus ER (+) patient groups, we found that in many instances these groups showed a different cytokine profile. These studies suggest that the IL-1 family of cytokines may be important in regulating protumorigenic activities within the HBC tumor microenvironment.
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