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Vaughan RA, Henry LK, Foster JD, Brown CR. Post-translational mechanisms in psychostimulant-induced neurotransmitter efflux. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2024; 99:1-33. [PMID: 38467478 DOI: 10.1016/bs.apha.2023.10.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
Abstract
The availability of monoamine neurotransmitters in the brain is under the control of dopamine, norepinephrine, and serotonin transporters expressed on the plasma membrane of monoaminergic neurons. By regulating transmitter levels these proteins mediate crucial functions including cognition, attention, and reward, and dysregulation of their activity is linked to mood and psychiatric disorders of these systems. Amphetamine-based transporter substrates stimulate non-exocytotic transmitter efflux that induces psychomotor stimulation, addiction, altered mood, hallucinations, and psychosis, thus constituting a major component of drug neurochemical and behavioral outcomes. Efflux is under the control of transporter post-translational modifications that synergize with other regulatory events, and this review will summarize our knowledge of these processes and their role in drug mechanisms.
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Affiliation(s)
- Roxanne A Vaughan
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, United States.
| | - L Keith Henry
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, United States
| | - James D Foster
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, United States
| | - Christopher R Brown
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, United States
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The complex interactions among serotonin, insulin, leptin, and glycolipid metabolic parameters in human obesity. CNS Spectr 2022; 27:99-108. [PMID: 32921339 DOI: 10.1017/s1092852920001820] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
OBJECTIVE To provide evidence to the link between serotonin (5-HT), energy metabolism, and the human obese phenotype, the present study investigated the binding and function of the platelet 5-HT transporter (SERT), in relation to circulating insulin, leptin, and glycolipid metabolic parameters. METHODS Seventy-four drug-free subjects were recruited on the basis of divergent body mass index (BMIs) (16.5-54.8 Kg/m2). All subjects were tested for their blood glycolipid profile together with platelet [3H]-paroxetine ([3H]-Par) binding and [3H]-5-HT reuptake measurements from April 1st to June 30th, 2019. RESULTS The [3H]-Par Bmax (fmol/mg proteins) was progressively reduced with increasing BMIs (P < .001), without changes in affinity. Moreover, Bmax was negatively correlated with BMI, waist/hip circumferences (W/HC), triglycerides (TD), glucose, insulin, and leptin, while positively with high-density lipoprotein (HDL) cholesterol (P < .01). The reduction of 5-HT uptake rate (Vmax, pmol/min/109 platelets) among BMI groups was not statistically significant, but Vmax negatively correlated with leptin and uptake affinity values (P < .05). Besides, [3H]-Par affinity values positively correlated with glycemia and TD, while [3H]-5-HT reuptake affinity with glycemia only (P < .05). Finally, these correlations were specific of obese subjects, while, from multiple linear-regression analysis conducted on all subjects, insulin (P = .006) resulting negatively related to Bmax independently from BMI. CONCLUSIONS Present findings suggest the presence of a possible alteration of insulin/5-HT/leptin axis in obesity, differentially impinging the density, function, and/or affinity of the platelet SERT, as a result of complex appetite/reward-related interactions between the brain, gut, pancreatic islets, and adipose tissue. Furthermore, they support the foremost cooperation of peptides and 5-HT in maintaining energy homeostasis.
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Blom T, Meinsma R, di Summa F, van den Akker E, van Kuilenburg ABP, Hansen M, Tytgat GAM. Thrombocytopenia after meta-iodobenzylguanidine (MIBG) therapy in neuroblastoma patients may be caused by selective MIBG uptake via the serotonin transporter located on megakaryocytes. EJNMMI Res 2021; 11:81. [PMID: 34424429 PMCID: PMC8382772 DOI: 10.1186/s13550-021-00823-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Accepted: 08/11/2021] [Indexed: 11/10/2022] Open
Abstract
Background The therapeutic use of [131I]meta-iodobenzylguanidine ([131I]MIBG) is often accompanied by hematological toxicity, primarily consisting of severe and persistent thrombocytopenia. We hypothesize that this is caused by selective uptake of MIBG via the serotonin transporter (SERT) located on platelets and megakaryocytes. In this study, we have investigated whether in vitro cultured human megakaryocytes are capable of selective plasma membrane transport of MIBG and whether pharmacological intervention with selective serotonin reuptake inhibitors (SSRIs) may prevent this radiotoxic MIBG uptake. Methods Peripheral blood CD34+ cells were differentiated to human megakaryocytic cells using a standardized culture protocol. Prior to [3H]serotonin and [125I]MIBG uptake experiments, the differentiation status of megakaryocyte cultures was assessed by flow cytometry. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to assess SERT and NET (norepinephrine transporter) mRNA expression. On day 10 of differentiation, [3H]serotonin and [125I]MIBG uptake assays were conducted. Part of the samples were co-incubated with the SSRI citalopram to assess SERT-specific uptake. HEK293 cells transfected with SERT, NET, and empty vector served as controls. Results In vitro cultured human megakaryocytes are capable of selective plasma membrane transport of MIBG. After 10 days of differentiation, megakaryocytic cell culture batches from three different hematopoietic stem and progenitor cell donors showed on average 9.2 ± 2.4 nmol of MIBG uptake per milligram protein per hour after incubation with 10–7 M MIBG (range: 6.6 ± 1.0 to 11.2 ± 1.0 nmol/mg/h). Co-incubation with the SSRI citalopram led to a significant reduction (30.1%—41.5%) in MIBG uptake, implying SERT-specific uptake of MIBG. A strong correlation between the number of mature megakaryocytes and SERT-specific MIBG uptake was observed. Conclusion Our study demonstrates that human megakaryocytes cultured in vitro are capable of MIBG uptake. Moreover, the SSRI citalopram selectively inhibits MIBG uptake via the serotonin transporter. The concomitant administration of citalopram to neuroblastoma patients during [131I]MIBG therapy might be a promising strategy to prevent the onset of thrombocytopenia. Supplementary Information The online version contains supplementary material available at 10.1186/s13550-021-00823-5.
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Affiliation(s)
- Thomas Blom
- Princess Máxima Center for Pediatric Oncology, Heidelberglaan 25, 3584 CS, Utrecht, The Netherlands. .,Department of Clinical Chemistry, Cancer Center Amsterdam, Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam University Medical Centers, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
| | - Rutger Meinsma
- Department of Clinical Chemistry, Cancer Center Amsterdam, Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam University Medical Centers, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands
| | - Franca di Summa
- Department of Hematopoiesis, Sanquin Research and Landsteiner Laboratory, Amsterdam University Medical Centers, University of Amsterdam, Plesmanlaan 125, 1066 CX, Amsterdam, The Netherlands
| | - Emile van den Akker
- Department of Hematopoiesis, Sanquin Research and Landsteiner Laboratory, Amsterdam University Medical Centers, University of Amsterdam, Plesmanlaan 125, 1066 CX, Amsterdam, The Netherlands
| | - André B P van Kuilenburg
- Department of Clinical Chemistry, Cancer Center Amsterdam, Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam University Medical Centers, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands
| | - Marten Hansen
- Department of Hematopoiesis, Sanquin Research and Landsteiner Laboratory, Amsterdam University Medical Centers, University of Amsterdam, Plesmanlaan 125, 1066 CX, Amsterdam, The Netherlands
| | - Godelieve A M Tytgat
- Princess Máxima Center for Pediatric Oncology, Heidelberglaan 25, 3584 CS, Utrecht, The Netherlands
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Blom T, Meinsma R, Rutgers M, Buitenhuis C, Dekken-Van den Burg M, van Kuilenburg ABP, Tytgat GAM. Selective serotonin reuptake inhibitors (SSRIs) prevent meta-iodobenzylguanidine (MIBG) uptake in platelets without affecting neuroblastoma tumor uptake. EJNMMI Res 2020; 10:78. [PMID: 32642907 PMCID: PMC7343696 DOI: 10.1186/s13550-020-00662-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 06/25/2020] [Indexed: 12/21/2022] Open
Abstract
Background The therapeutic use of [131I]meta-iodobenzylguanidine ([131I]MIBG) is often accompanied by hematological toxicity, mainly consisting of persistent and severe thrombocytopenia. While MIBG accumulates in neuroblastoma cells via selective uptake by the norepinephrine transporter (NET), the serotonin transporter (SERT) is responsible for cellular uptake of MIBG in platelets. In this study, we have investigated whether pharmacological intervention with selective serotonin reuptake inhibitors (SSRIs) may prevent radiotoxic MIBG uptake in platelets without affecting neuroblastoma tumor uptake. Methods To determine the transport kinetics of SERT for [125I]MIBG, HEK293 cells were transfected with SERT and uptake assays were conducted. Next, a panel of seven SSRIs was tested in vitro for their inhibitory potency on the uptake of [125I]MIBG in isolated human platelets and in cultured neuroblastoma cells. We investigated in vivo the efficacy of the four best performing SSRIs on the accumulation of [125I]MIBG in nude mice bearing subcutaneous neuroblastoma xenografts. In ex vivo experiments, the diluted plasma of mice treated with SSRIs was added to isolated human platelets to assess the effect on [125I]MIBG uptake. Results SERT performed as a low-affinity transporter of [125I]MIBG in comparison with NET (Km = 9.7 μM and 0.49 μM, respectively). Paroxetine was the most potent uptake inhibitor of both serotonin (IC50 = 0.6 nM) and MIBG (IC50 = 0.2 nM) in platelets. Citalopram was the most selective SERT inhibitor of [125I]MIBG uptake, with high SERT affinity in platelets (IC50 = 7.8 nM) and low NET affinity in neuroblastoma cells (IC50 = 11.940 nM). The in vivo tested SSRIs (citalopram, fluvoxamine, sertraline, and paroxetine) had no effect on [125I]MIBG uptake levels in neuroblastoma xenografts. In contrast, treatment with desipramine, a NET selective inhibitor, resulted in profoundly decreased xenograft [125I]MIBG levels (p < 0.0001). In ex vivo [125I]MIBG uptake experiments, 100- and 34-fold diluted murine plasma of mice treated with citalopram added to isolated human platelets led to a decrease in MIBG uptake of 54–76%, respectively. Conclusion Our study demonstrates for the first time that SSRIs selectively inhibit MIBG uptake in platelets without affecting MIBG accumulation in an in vivo neuroblastoma model. The concomitant application of citalopram during [131I]MIBG therapy seems a promising strategy to prevent thrombocytopenia in neuroblastoma patients.
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Affiliation(s)
- Thomas Blom
- Princess Máxima Center for Pediatric Oncology, Utrecht, The Netherlands.,Gastroenterology & Metabolism, Department of Clinical Chemistry, Amsterdam University Medical Center, Amsterdam, The Netherlands
| | - Rutger Meinsma
- Gastroenterology & Metabolism, Department of Clinical Chemistry, Amsterdam University Medical Center, Amsterdam, The Netherlands
| | - Marja Rutgers
- Department of Experimental Therapy, Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Corine Buitenhuis
- Department of Experimental Therapy, Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Marieke Dekken-Van den Burg
- Department of Pediatric Oncology, Emma Children's Hospital, Amsterdam University Medical Center, Amsterdam, The Netherlands
| | - André B P van Kuilenburg
- Gastroenterology & Metabolism, Department of Clinical Chemistry, Amsterdam University Medical Center, Amsterdam, The Netherlands
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Rudnick G, Sandtner W. Serotonin transport in the 21st century. J Gen Physiol 2019; 151:1248-1264. [PMID: 31570504 PMCID: PMC6829555 DOI: 10.1085/jgp.201812066] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 08/24/2019] [Indexed: 12/16/2022] Open
Abstract
Rudnick and Sandtner review the history of serotonin transporter research in light of structural and electrophysiological advances. Serotonin (5-hydroxytryptamine [5-HT]) is accumulated within nerve endings by the serotonin transporter (SERT), which terminates its extracellular action and provides cytoplasmic 5-HT for refilling of synaptic vesicles. SERT is the target for many antidepressant medications as well as psychostimulants such as cocaine and ecstasy (3,4-methylenedioxymethamphetamine). SERT belongs to the SLC6 family of ion-coupled transporters and is structurally related to several other transporter families. SERT was studied in the 1970s and 1980s using membrane vesicles isolated from blood platelets. These studies led to a proposed stoichiometry of transport that has been challenged by high-resolution structures of SERT and its homologues and by studies of SERT electrophysiology. Here, we review the original evidence alongside more recent structural and electrophysiological evidence. A self-consistent picture emerges with surprising insights into the ion fluxes that accompany 5-HT transport.
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Affiliation(s)
- Gary Rudnick
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT
| | - Walter Sandtner
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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Jin DC, Cao HL, Xu MQ, Wang SN, Wang YM, Yan F, Wang BM. Regulation of the serotonin transporter in the pathogenesis of irritable bowel syndrome. World J Gastroenterol 2016; 22:8137-8148. [PMID: 27688655 PMCID: PMC5037082 DOI: 10.3748/wjg.v22.i36.8137] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2016] [Revised: 05/28/2016] [Accepted: 06/15/2016] [Indexed: 02/06/2023] Open
Abstract
Serotonin (5-HT) and the serotonin transporter (SERT) have earned a tremendous amount of attention regarding the pathogenesis of irritable bowel syndrome (IBS). Considering that enteric 5-HT is responsible for the secretion, motility and perception of the bowel, the involvement of altered enteric 5-HT metabolism in the pathogenesis of IBS has been elucidated. Higher 5-HT availability is commonly associated with depressed SERT mRNA in patients with IBS compared with healthy controls. The expression difference of SERT between IBS patients and healthy controls might suggest that SERT plays an essential role in IBS pathogenesis, and SERT was expected to be a novel therapeutic target for IBS. Progress in this area has begun to illuminate the complex regulatory mechanisms of SERT in the etiology of IBS. In this article, current insights regarding the regulation of SERT in IBS are provided, including aspects of SERT gene polymorphisms, microRNAs, immunity and inflammation, gut microbiota, growth factors, among others. Potential SERT-directed therapies for IBS are also described. The potential regulators of SERT are of clinical importance and are important for better understanding IBS pathophysiology and therapeutic strategies.
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Rivera-Baltanas T, Olivares JM, Martinez-Villamarin JR, Fenton EY, Kalynchuk LE, Caruncho HJ. Serotonin 2A receptor clustering in peripheral lymphocytes is altered in major depression and may be a biomarker of therapeutic efficacy. J Affect Disord 2014; 163:47-55. [PMID: 24836087 DOI: 10.1016/j.jad.2014.03.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 03/06/2014] [Accepted: 03/07/2014] [Indexed: 12/28/2022]
Abstract
BACKGROUND In a previous report, we showed that the clustering of serotonin (5HT) transporter (SERT) protein on cell membranes of peripheral lymphocytes predicts responsivity to antidepressant medication in two subpopulations of naïve depression patients (Rivera-Baltanas et al., J Affect Disord, 2012, 137, 46-55). In this study, we extended this idea to 5-HT2A receptor clusters in a similar patient population. METHODS We collected blood samples from a subset of patients from our previous study on SERT clustering (20 untreated and newly diagnosed depression patients, and 20 matched control subjects). Blood samples were collected at the time of diagnosis and after 8 weeks of pharmacological treatment and at analogous times in control subjects. We used the Hamilton scale to quantify the level of depression in patients both before and after treatment. We then used immunocytochemistry to assess 5-HT2A receptor clusters in lymphocytes at the same time points. RESULTS We found that both the size and number of 5-HT2A receptor clusters were increased in naïve depression patients compared to control subjects. Interestingly, there were individual differences in the distribution of 5-HT2A receptor cluster size that allowed us to differentiate the depression patients into two subgroups: a D-I group and a D-II group. After 8 weeks of pharmacological treatment, patients in both groups showed an improvement of symptoms, but patients in the D-II group had a much better outcome with many of them showing remission of symptoms. Furthermore, although treatment decreased cluster number and size in both D-I and D-II groups, only the D-II patients showed an increase in the number of clusters within the modal peak. Importantly, the same patients that belonged in the D-I or D-II groups in the present report were also assigned to the same groups in our previous study on SERT clustering. LIMITATIONS The data should be replicated within a proper clinical trial. CONCLUSIONS 5-HT2A receptor clusters in peripheral lymphocytes are altered in major depression, partially reversed by antidepressant treatment, and may be considered a putative biomarker of therapeutic efficacy in major depression.
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Affiliation(s)
- Tania Rivera-Baltanas
- Department of Cell Biology, University of Santiago de Compostela, Spain; Hospital Meixoeiro, CHUVI, Vigo, Spain
| | | | | | - Erin Y Fenton
- Department of Psychology, University of Saskatchewan, Saskatoon, SK, Canada
| | - Lisa E Kalynchuk
- Department of Medicine, University of Saskatchewan, Saskatoon, SK, Canada
| | - Hector J Caruncho
- Department of Cell Biology, University of Santiago de Compostela, Spain; College of Pharmacy and Nutrition, University of Saskatchewan, Academic Health Sciences Bldg # 1B23, 107 Wiggins Road, Saskatoon, Saskatoon, SK, Canada S7N 5E5.
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Giannaccini G, Betti L, Palego L, Marsili A, Santini F, Pelosini C, Fabbrini L, Schmid L, Giusti L, Maffei M, Lanza M, Cristofaro M, Baroni S, Mauri M, Vitti P, Fierabracci P, Lucacchini A. The expression of platelet serotonin transporter (SERT) in human obesity. BMC Neurosci 2013; 14:128. [PMID: 24138674 PMCID: PMC4016247 DOI: 10.1186/1471-2202-14-128] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 10/09/2013] [Indexed: 01/20/2023] Open
Abstract
Background Serotonin (5-HT) is a well-known modulator of eating behavior. However, the molecular mechanisms linking its action to body weight balance have been only partially elucidated. Since platelets are a suitable peripheral model to study 5-HT transport, metabolism and release, we herein evaluated the expression of the platelet 5-HT re-uptake system (SERT) by [3H]-paroxetine binding assay. A cohort of 114 unrelated individuals (34 males, 80 females; age, mean ± SD: 38.57 ± 12.47 years) without major psychiatric disorders, was recruited following a naturalistic design regarding age or gender and classified accordingly to their body mass index (BMI). Subjects were divided into 5 groups: normal-weight (NW), overweight (OW) and grade I-III obese (OB) individuals. For gender analyses, data were transformed into [3H]-paroxetine density (Bmax)/BMI ratios to overcome both the disparity of women vs. men number and anthropometric differences between sexes. Results [3H]-paroxetine Bmax (SERT density, fmol/mg proteins) was reduced in platelet membranes of grade II (p < 0.01) and III (p < 0.001) obese subjects vs. controls and in overweight subjects (p < 0.05) vs. grade III obese individuals. Considering all patients together, a strong negative correlation between Bmax and BMI (r = −0.449; P < 0.0001) was demonstrated. Conversely, [3H]-paroxetine KD (dissociation constant, nM) did not differ among groups. No gender-related variation concerning Bmax/BMI ratios was observed in this cohort of subjects. Conclusions The down-regulation of SERT in platelet membranes of severe human obesity (BMI > 35 Kg/m2) confirms the involvement of 5-HT system in body weight gain. Moreover, this findings may help to elucidate those monoamine-endocrine networks acting on fat storage, adipocyte signaling and energy balance. Targeting 5-HT/5-HT-related markers will possibly uncover the existence of human obesity subtypes.
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Affiliation(s)
- Gino Giannaccini
- Department of Pharmacy, University of Pisa, via Bonanno 6, Pisa 56126-I, Italy.
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Harrington RA, Lee LC, Crum RM, Zimmerman AW, Hertz-Picciotto I. Serotonin Hypothesis of Autism: Implications for Selective Serotonin Reuptake Inhibitor Use during Pregnancy. Autism Res 2013; 6:149-68. [DOI: 10.1002/aur.1288] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Accepted: 02/15/2013] [Indexed: 11/11/2022]
Affiliation(s)
- Rebecca A. Harrington
- Department of Epidemiology; Johns Hopkins Bloomberg School of Public Health; Baltimore; Maryland
| | - Li-Ching Lee
- Department of Epidemiology; Johns Hopkins Bloomberg School of Public Health; Baltimore; Maryland
| | - Rosa M. Crum
- Departments of Epidemiology, Psychiatry, and Mental Health; Johns Hopkins Medical Institutions; Baltimore; Maryland
| | - Andrew W. Zimmerman
- Lurie Center for Autism; Massachusetts General Hospital for Children; Lexington; Massachusetts
| | - Irva Hertz-Picciotto
- Department of Public Health Sciences and the M.I.N.D. Institute; MS1C; University of California, Davis; Davis; California
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Ambrosio AL, Boyle JA, Di Pietro SM. Mechanism of platelet dense granule biogenesis: study of cargo transport and function of Rab32 and Rab38 in a model system. Blood 2012; 120:4072-81. [PMID: 22927249 PMCID: PMC3496959 DOI: 10.1182/blood-2012-04-420745] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 08/12/2012] [Indexed: 12/21/2022] Open
Abstract
Dense granules are important in platelet aggregation to form a hemostatic plug as evidenced by the increased bleeding time in mice and humans with dense granule deficiency. Dense granules also are targeted by antiplatelet agents because of their role in thrombus formation. Therefore, the molecular understanding of the dense granule and its biogenesis is of vital importance. In this work, we establish a human megakaryocytic cell line (MEG-01) as a model system for the study of dense granule biogenesis using a variety of cell biology and biochemical approaches. Using this model system, we determine the late endocytic origin of these organelles by colocalization of the internalized fluid phase marker dextran with both mepacrine and transmembrane dense granule proteins. By mistargeting of mutant dense granule proteins, we demonstrate that sorting signals recognized by adaptor protein-3 are necessary for normal transport to dense granules. Furthermore, we show that tissue-specific Rab32 and Rab38 are crucial for the fusion of vesicles containing dense granule cargo with the maturing organelle. This work sheds light on the biogenesis of dense granules at the molecular level and opens the possibility of using this powerful model system for the investigation of new components of the biogenesis machinery.
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Affiliation(s)
- Andrea L Ambrosio
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870, USA
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Serotonin transporter clustering in blood lymphocytes as a putative biomarker of therapeutic efficacy in major depressive disorder. J Affect Disord 2012; 137:46-55. [PMID: 22257570 DOI: 10.1016/j.jad.2011.12.041] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Revised: 12/21/2011] [Accepted: 12/22/2011] [Indexed: 12/13/2022]
Abstract
BACKGROUND Serotonin transporter (SERT) binding is decreased in lymphocytes of depression patients and this decrease is partially reversed by antidepressant medication. However, recent evidence has shown that clustering of SERT on cell membranes is very important for receptor functionality. Alteration in SERT clustering on peripheral lymphocytes does not affect symptoms severity. At the most it is associated or predicts responsivity to treatment. METHODS We collected blood samples from 38 untreated and newly diagnosed depression patients at the time of diagnosis and after 8weeks of pharmacological treatment and of 38 control subjects. We used the Hamilton Scale to quantify the level of depression in patients both before and after pharmacological treatment. We then used immunocytochemistry to assess SERT protein clusters in lymphocyte blood samples. RESULTS We found an increase in SERT cluster size, but not the number of SERT clusters, in naïve depression patients compared to control subjects. Based on the distribution of SERT cluster size we differentiated the naïve depression patients into two groups (D-I and D-II). Naïve D-I and D-II patients initially showed similar Hamilton scores. However, after pharmacological treatment the D-II patients showed a greater decrease in Hamilton scores than did the D-I patients, and they had an increase in the number of SERT clusters. LIMITATIONS The data should be replicated in a larger cohort of patients and with a proper clinical trial. CONCLUSIONS We propose that SERT clustering in blood lymphocytes may be a putative biomarker for antidepressant efficacy in major depressive disorder.
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Differential expression of neuronal dopamine and serotonin transporters DAT and SERT in megakaryocytes and platelets generated from human MEG-01 megakaryoblasts. Cell Tissue Res 2011; 346:151-61. [PMID: 22006250 DOI: 10.1007/s00441-011-1256-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Accepted: 09/16/2011] [Indexed: 10/16/2022]
Abstract
In the central nervous system, serotonergic and dopaminergic signaling is terminated by the activity of specialized transporter proteins for serotonin (SERT) and dopamine (DAT). These transporter proteins are found both on the cell surface and in intracellular transport vesicles. Trafficking between these subcellular domains regulates the efficiency of removal of extracellular neurotransmitters and hence the efficacy of neuronal signaling. Therefore, it is of high interest to gain more insight into the regulatory mechanisms of the human DAT and SERT cell surface expression in their natural surroundings, i.e., in human cells. Because it is not possible to cultivate human neuronal cells expressing these transporter proteins, there is a need to find other human cells expressing these neuronal proteins. Here, we have investigated the expression of human SERT and DAT on developing megakaryocytes and platelet-like particles derived from the megakaryocyte progenitor cell line MEG-01 upon differentiation by valproic acid (VPA) and all-trans retinoic acid (ATRA). Our results show that MEG-01 cells express SERT and DAT and that VPA and ATRA induce a significant increase of transporter expression on developing megakaryocytes and platelets. As compared to ATRA, VPA more efficiently induced SERT expression but not DAT expression. Comparable to naïve platelets and neurons, SERT was localized to both the cell surface and intracellular compartments. Hence, VPA and ATRA-treated MEG-01 cells provide a model well-suited to studying neuronal monoamine transporter expression, not only during transcription and translation but also with respect to protein trafficking to and from the cell surface.
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Thornton S, Schedel A, Besenfelder S, Klüter H, Bugert P. Cholinergic drugs inhibit in vitro megakaryopoiesis via the alpha7-nicotinic acetylcholine receptor. Platelets 2011; 22:390-5. [DOI: 10.3109/09537104.2010.551304] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Giannaccini G, Betti L, Palego L, Pirone A, Schmid L, Lanza M, Fabbrini L, Pelosini C, Maffei M, Santini F, Pinchera A, Lucacchini A. Serotonin transporter (SERT) and translocator protein (TSPO) expression in the obese ob/ob mouse. BMC Neurosci 2011; 12:18. [PMID: 21299850 PMCID: PMC3044656 DOI: 10.1186/1471-2202-12-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Accepted: 02/07/2011] [Indexed: 02/03/2023] Open
Abstract
Background An ever growing body of evidences is emerging concerning metabolism hormones, neurotransmitters or stress-related biomarkers as effective modulators of eating behavior and body weight in mammals. The present study sought at examining the density and affinity of two proteins related to neurotransmission and cell metabolism, the serotonin transporter SERT and the cholesterol import-benzodiazepine site TSPO (translocator protein), in a rodent leptin-lacking mutant, the obese ob/ob mouse. Binding studies were thus carried out in brain or peripheral tissues, blood platelets (SERT) and kidneys (TSPO), of ob/ob and WT mice supplied with a standard diet, using the selective radiochemical ligands [3H]-paroxetine and [3H]-PK11195. Results We observed comparable SERT number or affinity in brain and platelets of ob/ob and WT mice, whilst a significantly higher [3H]-PK11195 density was reported in the brain of ob/ob animals. TSPO binding parameters were similar in the kidneys of all tested mice. By [3H]-PK11195 autoradiography of coronal hypothalamic-hippocampal sections, an increased TSPO signal was detected in the dentate gyrus (hippocampus) and choroids plexus of ob/ob mice, without appreciable changes in the cortex or hypothalamic-thalamic regions. Conclusions These findings show that TSPO expression is up-regulated in cerebral regions of ob/ob leptin-deficient mice, suggesting a role of the translocator protein in leptin-dependent CNS trophism and metabolism. Unchanged SERT in mutant mice is discussed herein in the context of previous literature as the forerunner to a deeper biochemical investigation.
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Affiliation(s)
- Gino Giannaccini
- Department of Psychiatry, Neurobiology, Pharmacology and Biotechnology, University of Pisa, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy.
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