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Sweedler JV. Are We Virtual Yet? Anal Chem 2013; 85:3463. [DOI: 10.1021/ac400772a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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227
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Nemes P, Rubakhin SS, Aerts JT, Sweedler JV. Qualitative and quantitative metabolomic investigation of single neurons by capillary electrophoresis electrospray ionization mass spectrometry. Nat Protoc 2013; 8:783-99. [PMID: 23538882 PMCID: PMC3655804 DOI: 10.1038/nprot.2013.035] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Single-cell mass spectrometry (MS) empowers metabolomic investigations by decreasing analytical dimensions to the size of individual cells and subcellular structures. We describe a protocol for investigating and quantifying metabolites in individual isolated neurons using single-cell capillary electrophoresis (CE) coupled to electrospray ionization (ESI) time-of-flight (TOF) MS. The protocol requires ∼2 h for sample preparation, neuron isolation and metabolite extraction, and 1 h for metabolic measurement. We used the approach to detect more than 300 distinct compounds in the mass range of typical metabolites in various individual neurons (25-500 μm in diameter) isolated from the sea slug (Aplysia californica) central and rat (Rattus norvegicus) peripheral nervous systems. We found that a subset of identified compounds was sufficient to reveal metabolic differences among freshly isolated neurons of different types and changes in the metabolite profiles of cultured neurons. The protocol can be applied to the characterization of the metabolome in a variety of smaller cells and/or subcellular domains.
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Sweedler JV. Pittcon: Still Vibrant after More than 60 Years. Anal Chem 2013. [DOI: 10.1021/ac4004634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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229
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Knolhoff AM, Nautiyal KM, Nemes P, Kalachikov S, Morozova I, Silver R, Sweedler JV. Combining small-volume metabolomic and transcriptomic approaches for assessing brain chemistry. Anal Chem 2013; 85:3136-43. [PMID: 23409944 PMCID: PMC3605826 DOI: 10.1021/ac3032959] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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The integration of disparate data
types provides a more complete
picture of complex biological systems. Here we combine small-volume
metabolomic and transcriptomic platforms to determine subtle chemical
changes and to link metabolites and genes to biochemical pathways.
Capillary electrophoresis–mass spectrometry (CE–MS)
and whole-genome gene expression arrays, aided by integrative pathway
analysis, were utilized to survey metabolomic/transcriptomic hippocampal
neurochemistry. We measured changes in individual hippocampi from
the mast cell mutant mouse strain, C57BL/6 KitW-sh/W-sh. These mice have a
naturally occurring mutation in the white spotting locus that causes
reduced c-Kit receptor expression and an inability of mast cells to
differentiate from their hematopoietic progenitors. Compared with
their littermates, the mast cell-deficient mice have profound deficits
in spatial learning, memory, and neurogenesis. A total of 18 distinct
metabolites were identified in the hippocampus that discriminated
between the C57BL/6 KitW-sh/W-sh and control mice. The combined analysis of metabolite and
gene expression changes revealed a number of altered pathways. Importantly,
results from both platforms indicated that multiple pathways are impacted,
including amino acid metabolism, increasing the confidence in each
approach. Because the CE–MS and expression profiling are both
amenable to small-volume analysis, this integrated analysis is applicable
to a range of volume-limited biological systems.
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Lanni EJ, Rubakhin SS, Sweedler JV. Visualizing the proteome: mapping protein changes in disease states with mass spectrometry imaging. J Neurochem 2013; 124:581-3. [DOI: 10.1111/jnc.12037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Accepted: 09/25/2012] [Indexed: 11/29/2022]
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231
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Sweedler JV. Meet the Analytical Chemistry Editorial Advisory Board. Anal Chem 2013. [DOI: 10.1021/ac4001173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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232
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Fazal Z, Southey BR, Sweedler JV, Rodriguez-Zas SL. Multifactorial Understanding of Ion Abundance in Tandem Mass Spectrometry Experiments. JOURNAL OF PROTEOMICS & BIOINFORMATICS 2013; 6:23-29. [PMID: 24031159 PMCID: PMC3768159 DOI: 10.4172/jpb.1000256] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In a bottom-up shotgun approach, the proteins of a mixture are enzymatically digested, separated, and analyzed via tandem mass spectrometry. The mass spectra relating fragment ion intensities (abundance) to the mass-to-charge are used to deduce the amino acid sequence and identify the peptides and proteins. The variables that influence intensity were characterized using a multi-factorial mixed-effects model, a ten-fold cross-validation, and stepwise feature selection on 6,352,528 fragment ions from 61,543 peptide ions. Intensity was higher in fragment ions that did not have neutral mass loss relative to any mass loss or that had a +1 charge state. Peptide ions classified for proton mobility as non-mobile had lowest intensity of all mobility levels. Higher basic residue (arginine, lysine or histidine) counts in the peptide ion and low counts in the fragment ion were associated with lower fragment ion intensities. Higher counts of proline in peptide and fragment ions were associated with lower intensities. These results are consistent with the mobile proton theory. Opposite trends between peptide and fragment ion counts and intensity may be due to the different impact of factor under consideration at different stages of the MS/MS experiment or to the different distribution of observations across peptide and fragment ion levels. Presence of basic residues at all three positions next to the fragmentation site was associated with lower fragment ion intensity. The presence of proline proximal to the fragmentation site enhanced fragmentation and had the opposite trend when located distant from the site. A positive association between fragment ion intensity and presence of sulfur residues (cysteine and methionine) on the vicinity of the fragmentation site was identified. These results highlight the multi-factorial nature of fragment ion intensity and could improve the algorithms for peptide identification and the simulation in tandem mass spectrometry experiments.
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233
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Lee JE, Zamdborg L, Southey BR, Atkins N, Mitchell JW, Li M, Gillette MU, Kelleher NL, Sweedler JV. Quantitative peptidomics for discovery of circadian-related peptides from the rat suprachiasmatic nucleus. J Proteome Res 2013; 12:585-93. [PMID: 23256577 DOI: 10.1021/pr300605p] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
In mammals the suprachiasmatic nucleus (SCN), the master circadian clock, is sensitive to light input via the optic chiasm and synchronizes many daily biological rhythms. Here we explore variations in the expression levels of neuropeptides present in the SCN of rats using a label-free quantification approach that is based on integrating peak intensities between daytime, Zeitgeber time (ZT) 6, and nighttime, ZT 18. From nine analyses comparing the levels between these two time points, 10 endogenous peptides derived from eight prohormones exhibited significant differences in their expression levels (adjusted p-value <0.05). Of these, seven peptides derived from six prohormones, including GRP, PACAP, and CART, exhibited ≥ 30% increases at ZT 18, and the VGRPEWWMDYQ peptide derived from proenkephalin A showed a >50% increase at nighttime. Several endogenous peptides showing statistically significant changes in this study have not been previously reported to alter their levels as a function of time of day, nor have they been implicated in prior functional SCN studies. This information on peptide expression changes serves as a resource for discovering unknown peptide regulators that affect circadian rhythms in the SCN.
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Sweedler JV. Rejections with Editorial Expertise and Without External Review: Are These Fair? Anal Chem 2012. [DOI: 10.1021/ac303246t] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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236
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Hou X, Xie F, Sweedler JV. Relative quantitation of neuropeptides over a thousand-fold concentration range. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:2083-93. [PMID: 22993045 PMCID: PMC3515743 DOI: 10.1007/s13361-012-0481-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 08/16/2012] [Accepted: 08/17/2012] [Indexed: 05/23/2023]
Abstract
Neuropeptides are essential cell-to-cell signaling molecules that influence diverse regulatory and behavioral functions within biological systems. Differing in their amino acid sequences and post-translational modifications, hundreds of neuropeptides are produced via a series of enzymatic processing steps, and their levels vary with location, time, and physiological condition. Due to their wide range of endogenous concentrations and inherent chemical complexity, using mass spectrometry (MS) to accurately quantify changes in peptide levels can be challenging. Here we evaluate three different MS systems for their ability to accurately measure neuropeptide levels: capillary liquid chromatography-electrospray ionization-ion trap (CapLC-ESI-IT) MS, ultraperformance liquid chromatography-electrospray ionization-quadrupole-time-of-flight (UPLC-LC-ESI-Q-TOF) MS, and matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) MS. Specifically, eight sample mixtures composed of five neuropeptide standards, with four technical replicates of each, were labeled with H(4)/D(4)-succinic anhydride, followed by relative peptide quantitation using the three MS platforms. For these samples, the CapLC-ESI-IT MS platform offered the most robust ability to accurately quantify peptides over a concentration range of 1200-fold, although it required larger sample sizes than the other two platforms. Both the UPLC-ESI-Q-TOF MS and the MALDI-TOF MS systems had lower limits of quantification, with the MALDI-TOF having the lowest. By implementing several data acquisition schemes and optimizing the data analysis approaches, we were able to accurately quantify peptides over a three orders of magnitude concentration range using either the UPLC or MALDI-TOF platforms. Overall these results increase our understanding of both the capabilities and limits of using MS-based approaches to measure peptides.
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Porter KI, Southey BR, Sweedler JV, Rodriguez-Zas SL. First survey and functional annotation of prohormone and convertase genes in the pig. BMC Genomics 2012; 13:582. [PMID: 23153308 PMCID: PMC3499383 DOI: 10.1186/1471-2164-13-582] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Accepted: 06/22/2012] [Indexed: 11/18/2022] Open
Abstract
Background The pig is a biomedical model to study human and livestock traits. Many of these traits are controlled by neuropeptides that result from the cleavage of prohormones by prohormone convertases. Only 45 prohormones have been confirmed in the pig. Sequence homology can be ineffective to annotate prohormone genes in sequenced species like the pig due to the multifactorial nature of the prohormone processing. The goal of this study is to undertake the first complete survey of prohormone and prohormone convertases genes in the pig genome. These genes were functionally annotated based on 35 gene expression microarray experiments. The cleavage sites of prohormone sequences into potentially active neuropeptides were predicted. Results We identified 95 unique prohormone genes, 2 alternative calcitonin-related sequences, 8 prohormone convertases and 1 cleavage facilitator in the pig genome 10.2 assembly and trace archives. Of these, 11 pig prohormone genes have not been reported in the UniProt, UniGene or Gene databases. These genes are intermedin, cortistatin, insulin-like 5, orexigenic neuropeptide QRFP, prokineticin 2, prolactin-releasing peptide, parathyroid hormone 2, urocortin, urocortin 2, urocortin 3, and urotensin 2-related peptide. In addition, a novel neuropeptide S was identified in the pig genome correcting the previously reported pig sequence that is identical to the rabbit sequence. Most differentially expressed prohormone genes were under-expressed in pigs experiencing immune challenge relative to the un-challenged controls, in non-pregnant relative to pregnant sows, in old relative to young embryos, and in non-neural relative to neural tissues. The cleavage prediction based on human sequences had the best performance with a correct classification rate of cleaved and non-cleaved sites of 92% suggesting that the processing of prohormones in pigs is similar to humans. The cleavage prediction models did not find conclusive evidence supporting the production of the bioactive neuropeptides urocortin 2, urocortin 3, torsin family 2 member A, tachykinin 4, islet amyloid polypeptide, and calcitonin receptor-stimulating peptide 2 in the pig. Conclusions The present genomic and functional characterization supports the use of the pig as an effective animal model to gain a deeper understanding of prohormones, prohormone convertases and neuropeptides in biomedical and agricultural research.
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Groenen MAM, Archibald AL, Uenishi H, Tuggle CK, Takeuchi Y, Rothschild MF, Rogel-Gaillard C, Park C, Milan D, Megens HJ, Li S, Larkin DM, Kim H, Frantz LAF, Caccamo M, Ahn H, Aken BL, Anselmo A, Anthon C, Auvil L, Badaoui B, Beattie CW, Bendixen C, Berman D, Blecha F, Blomberg J, Bolund L, Bosse M, Botti S, Bujie Z, Bystrom M, Capitanu B, Carvalho-Silva D, Chardon P, Chen C, Cheng R, Choi SH, Chow W, Clark RC, Clee C, Crooijmans RPMA, Dawson HD, Dehais P, De Sapio F, Dibbits B, Drou N, Du ZQ, Eversole K, Fadista J, Fairley S, Faraut T, Faulkner GJ, Fowler KE, Fredholm M, Fritz E, Gilbert JGR, Giuffra E, Gorodkin J, Griffin DK, Harrow JL, Hayward A, Howe K, Hu ZL, Humphray SJ, Hunt T, Hornshøj H, Jeon JT, Jern P, Jones M, Jurka J, Kanamori H, Kapetanovic R, Kim J, Kim JH, Kim KW, Kim TH, Larson G, Lee K, Lee KT, Leggett R, Lewin HA, Li Y, Liu W, Loveland JE, Lu Y, Lunney JK, Ma J, Madsen O, Mann K, Matthews L, McLaren S, Morozumi T, Murtaugh MP, Narayan J, Nguyen DT, Ni P, Oh SJ, Onteru S, Panitz F, Park EW, Park HS, Pascal G, Paudel Y, Perez-Enciso M, Ramirez-Gonzalez R, Reecy JM, Rodriguez-Zas S, Rohrer GA, Rund L, Sang Y, Schachtschneider K, Schraiber JG, Schwartz J, Scobie L, Scott C, Searle S, Servin B, Southey BR, Sperber G, Stadler P, Sweedler JV, Tafer H, Thomsen B, Wali R, Wang J, Wang J, White S, Xu X, Yerle M, Zhang G, Zhang J, Zhang J, Zhao S, Rogers J, Churcher C, Schook LB. Analyses of pig genomes provide insight into porcine demography and evolution. Nature 2012; 491:393-8. [PMID: 23151582 PMCID: PMC3566564 DOI: 10.1038/nature11622] [Citation(s) in RCA: 947] [Impact Index Per Article: 78.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2012] [Accepted: 09/27/2012] [Indexed: 01/03/2023]
Abstract
For 10,000 years pigs and humans have shared a close and complex relationship. From domestication to modern breeding practices, humans have shaped the genomes of domestic pigs. Here we present the assembly and analysis of the genome sequence of a female domestic Duroc pig (Sus scrofa) and a comparison with the genomes of wild and domestic pigs from Europe and Asia. Wild pigs emerged in South East Asia and subsequently spread across Eurasia. Our results reveal a deep phylogenetic split between European and Asian wild boars ∼1 million years ago, and a selective sweep analysis indicates selection on genes involved in RNA processing and regulation. Genes associated with immune response and olfaction exhibit fast evolution. Pigs have the largest repertoire of functional olfactory receptor genes, reflecting the importance of smell in this scavenging animal. The pig genome sequence provides an important resource for further improvements of this important livestock species, and our identification of many putative disease-causing variants extends the potential of the pig as a biomedical model.
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239
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Romanova EV, Sasaki K, Alexeeva V, Vilim FS, Jing J, Richmond TA, Weiss KR, Sweedler JV. Urotensin II in invertebrates: from structure to function in Aplysia californica. PLoS One 2012; 7:e48764. [PMID: 23144960 PMCID: PMC3493602 DOI: 10.1371/journal.pone.0048764] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2012] [Accepted: 10/05/2012] [Indexed: 02/07/2023] Open
Abstract
Neuropeptides are ancient signaling molecules that are involved in many aspects of organism homeostasis and function. Urotensin II (UII), a peptide with a range of hormonal functions, previously has been reported exclusively in vertebrates. Here, we provide the first direct evidence that UII-like peptides are also present in an invertebrate, specifically, the marine mollusk Aplysia californica. The presence of UII in the central nervous system (CNS) of Aplysia implies a more ancient gene lineage than vertebrates. Using representational difference analysis, we identified an mRNA of a protein precursor that encodes a predicted neuropeptide, we named Aplysia urotensin II (apUII), with a sequence and structural similarity to vertebrate UII. With in-situ hybridization and immunohistochemistry, we mapped the expression of apUII mRNA and its prohormone in the CNS and localized apUII-like immunoreactivity to buccal sensory neurons and cerebral A-cluster neurons. Mass spectrometry performed on individual isolated neurons, and tandem mass spectrometry on fractionated peptide extracts, allowed us to define the posttranslational processing of the apUII neuropeptide precursor and confirm the highly conserved cyclic nature of the mature neuropeptide apUII. Electrophysiological analysis of the central effects of a synthetic apUII suggests it plays a role in satiety and/or aversive signaling in feeding behaviors. Finding the homologue of vertebrate UII in the numerically small CNS of an invertebrate animal model is important for gaining insights into the molecular mechanisms and pathways mediating the bioactivity of UII in the higher metazoan.
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240
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Sweedler JV, Koppenaal DW. Analytical Chemistry: The Synergies between the Division and the Journal. Anal Chem 2012. [DOI: 10.1021/ac302945v] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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241
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Akhtar MN, Southey BR, Andrén PE, Sweedler JV, Rodriguez-Zas SL. Evaluation of database search programs for accurate detection of neuropeptides in tandem mass spectrometry experiments. J Proteome Res 2012; 11:6044-55. [PMID: 23082934 PMCID: PMC3516866 DOI: 10.1021/pr3007123] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
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Neuropeptide identification in mass spectrometry experiments
using
database search programs developed for proteins is challenging. Unlike
proteins, the detection of the complete sequence using a single spectrum
is required to identify neuropeptides or prohormone peptides. This
study compared the performance of three open-source programs used
to identify proteins, OMSSA, X!Tandem and Crux, to identify prohormone
peptides. From a target database of 7850 prohormone peptides, 23550
query spectra were simulated across different scenarios. Crux was
the only program that correctly matched all peptides regardless of p-value and at p-value < 1 × 10–2, 33%, 64%, and >75%, of the 5, 6, and ≥7
amino
acid-peptides were detected. Crux also had the best performance in
the identification of peptides from chimera spectra and in a variety
of missing ion scenarios. OMSSA, X!Tandem and Crux correctly detected
98.9% (99.9%), 93.9% (97.4%) and 88.7% (98.3%) of the peptides at E- or p-value < 1 × 10–6 (< 1 × 10–2), respectively. OMSSA and
X!Tandem outperformed the other programs in significance level and
computational speed, respectively. A consensus approach is not recommended
because some prohormone peptides were only identified by one program.
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242
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Tucker KR, Li Z, Rubakhin SS, Sweedler JV. Secondary ion mass spectrometry imaging of molecular distributions in cultured neurons and their processes: comparative analysis of sample preparation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:1931-8. [PMID: 22930440 PMCID: PMC3475608 DOI: 10.1007/s13361-012-0472-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 08/07/2012] [Accepted: 08/09/2012] [Indexed: 05/24/2023]
Abstract
Neurons often exhibit a complex chemical distribution and topography; therefore, sample preparation protocols that preserve structures ranging from relatively large cell somata to small neurites and growth cones are important factors in secondary ion mass spectrometry (SIMS) imaging studies. Here, SIMS was used to investigate the subcellular localization of lipids and lipophilic species in neurons from Aplysia californica. Using individual neurons cultured on silicon wafers, we compared and optimized several SIMS sampling approaches. After an initial step to remove the high salt culturing media, formaldehyde, paraformaldehyde, and glycerol, and various combinations thereof, were tested for their ability to achieve cell stabilization during and after the removal of extracellular media. These treatments improved the preservation of cellular morphology as visualized with SIMS imaging. For analytes >250 Da, coating the cell surface with a 3.2 nm-thick gold layer increased the ion intensity; multiple analytes previously not observed or observed at low abundance were detected, including intact cholesterol and vitamin E molecular ions. However, once a sample was coated, many of the lower molecular mass (<200 Da) analyte signals were suppressed. The optimum approach depended on the analyte being studied; the approaches evaluated included rinsing with water and cell stabilization with glycerol and 4 % paraformaldehyde. The sample preparation methods described here enhance SIMS imaging of processes of individual cultured neurons over a broad mass range with enhanced image contrast.
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Nemes P, Knolhoff AM, Rubakhin SS, Sweedler JV. Single-cell metabolomics: changes in the metabolome of freshly isolated and cultured neurons. ACS Chem Neurosci 2012; 3:782-92. [PMID: 23077722 PMCID: PMC3474288 DOI: 10.1021/cn300100u] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Accepted: 08/24/2012] [Indexed: 02/07/2023] Open
Abstract
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Metabolites are involved in a diverse range of intracellular
processes,
including a cell’s response to a changing extracellular environment.
Using single-cell capillary electrophoresis coupled to electrospray
ionization mass spectrometry, we investigated how placing individual
identified neurons in culture affects their metabolic profile. First,
glycerol-based cell stabilization was evaluated using metacerebral
neurons from Aplysia californica; the
measurement error was reduced from ∼24% relative standard deviation
to ∼6% for glycerol-stabilized cells compared to those isolated
without glycerol stabilization. In order to determine the changes
induced by culturing, 14 freshly isolated and 11 overnight-cultured
neurons of two metabolically distinct cell types from A. californica, the B1 and B2 buccal neurons, were
characterized. Of the more than 300 distinctive cell-related signals
detected, 35 compounds were selected for their known biological roles
and compared among each measured cell. Unsupervised multivariate and
statistical analysis revealed robust metabolic differences between
these two identified neuron types. We then compared the changes induced
by overnight culturing; metabolite concentrations were distinct for
26 compounds in the cultured B1 cells. In contrast, culturing had
less influence on the metabolic profile of the B2 neurons, with only
five compounds changing significantly. As a result of these culturing-induced
changes, the metabolic composition of the B1 neurons became indistinguishable
from the cultured B2 cells. This observation suggests that the two
cell types differentially regulate their in vivo or in vitro metabolomes in response to a changing environment.
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Croushore CA, Supharoek SA, Lee CY, Jakmunee J, Sweedler JV. Microfluidic device for the selective chemical stimulation of neurons and characterization of peptide release with mass spectrometry. Anal Chem 2012; 84:9446-52. [PMID: 23004687 PMCID: PMC3490451 DOI: 10.1021/ac302283u] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Neuropeptides are synthesized in and released from neurons and are involved in a wide range of physiological processes, including temperature homeostasis, learning, memory, and disease. When working with sparse neuronal networks, the ability to collect and characterize small sample volumes is important as neurons often release only a small proportion of their mass-limited content. Microfluidic systems are well suited for the study of neuropeptides. They offer the ability to control and manipulate the extracellular environment and small sample volumes, thereby reducing the dilution of peptides following release. We present an approach for the culture and stimulation of a neuronal network within a microfluidic device, subsequent collection of the released peptides, and their detection via mass spectrometry. The system employs microvalve-controlled stimulation channels to selectively stimulate a low-density neuronal culture, allowing us to determine the temporal onset of peptide release. Released peptides from the well-characterized, peptidergic bag cell neurons of Aplysia californica were collected and their temporal pattern of release was characterized with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. We show a robust difference in the timing of release for chemical solutions containing elevated K(+) (7 ± 3 min), when compared to insulin (19 ± 7 min) (p < 0.000 01).
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Romanova EV, Lee JE, Kelleher NL, Sweedler JV, Gulley JM. Comparative peptidomics analysis of neural adaptations in rats repeatedly exposed to amphetamine. J Neurochem 2012; 123:276-87. [PMID: 22860605 PMCID: PMC3463764 DOI: 10.1111/j.1471-4159.2012.07912.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 08/02/2012] [Accepted: 08/03/2012] [Indexed: 01/29/2023]
Abstract
Repeated exposure to amphetamine (AMPH) induces long-lasting behavioral changes, referred to as sensitization, that are accompanied by various neuroadaptations in the brain. To investigate the chemical changes that occur during behavioral sensitization, we applied a comparative proteomics approach to screen for neuropeptide changes in a rodent model of AMPH-induced sensitization. By measuring peptide profiles with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and comparing signal intensities using principal component analysis and variance statistics, subsets of peptides are found with significant differences in the dorsal striatum, nucleus accumbens, and medial prefrontal cortex of AMPH-sensitized male Sprague-Dawley rats. These biomarker peptides, identified in follow-up analyses using liquid chromatography and tandem mass spectrometry, suggest that behavioral sensitization to AMPH is associated with complex chemical adaptations that regulate energy/metabolism, neurotransmission, apoptosis, neuroprotection, and neuritogenesis, as well as cytoskeleton integrity and neuronal morphology. Our data contribute to a growing number of reports showing that in addition to the mesolimbic dopamine system, which is the best known signaling pathway involved with reinforcing the effect of psychostimulants, concomitant chemical changes in other pathways and in neuronal organization may play a part in the overall effect of chronic AMPH exposure on behavior.
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Wang TA, Yu YV, Govindaiah G, Ye X, Artinian L, Coleman TP, Sweedler JV, Cox CL, Gillette MU. Circadian rhythm of redox state regulates excitability in suprachiasmatic nucleus neurons. Science 2012; 337:839-42. [PMID: 22859819 PMCID: PMC3490628 DOI: 10.1126/science.1222826] [Citation(s) in RCA: 163] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Daily rhythms of mammalian physiology, metabolism, and behavior parallel the day-night cycle. They are orchestrated by a central circadian clock in the brain, the suprachiasmatic nucleus (SCN). Transcription of clock genes is sensitive to metabolic changes in reduction and oxidation (redox); however, circadian cycles in protein oxidation have been reported in anucleate cells, where no transcription occurs. We investigated whether the SCN also expresses redox cycles and how such metabolic oscillations might affect neuronal physiology. We detected self-sustained circadian rhythms of SCN redox state that required the molecular clockwork. The redox oscillation could determine the excitability of SCN neurons through nontranscriptional modulation of multiple potassium (K(+)) channels. Thus, dynamic regulation of SCN excitability appears to be closely tied to metabolism that engages the clockwork machinery.
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Park D, Hou X, Sweedler JV, Taghert PH. Therapeutic peptide production in Drosophila. Peptides 2012; 36:251-6. [PMID: 22595312 PMCID: PMC3402651 DOI: 10.1016/j.peptides.2012.05.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Revised: 05/07/2012] [Accepted: 05/07/2012] [Indexed: 11/23/2022]
Abstract
Bioactive peptides are important therapeutic drugs, yet conventional methods of peptide synthesis are challenged to meet increasing demand. We developed a novel and efficient means of metabolic engineering: therapeutic peptide production in Drosophila and as a proof of concept, we demonstrate production of fully matured human insulin. This in vivo system offers an innovative means to produce valuable bioactive peptides for therapies, its inherent flexibility facilitates drug development, and its ease of producing fully processed peptides simplifies metabolic engineering of new peptide products.
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248
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Yin P, Knolhoff AM, Rosenberg HJ, Millet LJ, Gillette MU, Sweedler JV. Peptidomic analyses of mouse astrocytic cell lines and rat primary cultured astrocytes. J Proteome Res 2012; 11:3965-73. [PMID: 22742998 DOI: 10.1021/pr201066t] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Astrocytes play an active role in the modulation of synaptic transmission by releasing cell-cell signaling molecules in response to various stimuli that evoke a Ca2+ increase. We expand on recent studies of astrocyte intracellular and secreted proteins by examining the astrocyte peptidome in mouse astrocytic cell lines and rat primary cultured astrocytes, as well as those peptides secreted from mouse astrocytic cell lines in response to Ca2+-dependent stimulations. We identified 57 peptides derived from 24 proteins with LC-MS/MS and CE-MS/MS in the astrocytes. Among the secreted peptides, four peptides derived from elongation factor 1, macrophage migration inhibitory factor, peroxiredoxin-5, and galectin-1 were putatively identified by mass-matching to peptides confirmed to be found in astrocytes. Other peptides in the secretion study were mass-matched to those found in prior peptidomics analyses on mouse brain tissue. Complex peptide profiles were observed after stimulation, suggesting that astrocytes are actively involved in peptide secretion. Twenty-six peptides were observed in multiple stimulation experiments but not in controls and thus appear to be released in a Ca2+-dependent manner. These results can be used in future investigations to better understand stimulus-dependent mechanisms of astrocyte peptide secretion.
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249
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Cecala C, Rubakhin SS, Mitchell JW, Gillette MU, Sweedler JV. A hyphenated optical trap capillary electrophoresis laser induced native fluorescence system for single-cell chemical analysis. Analyst 2012; 137:2965-72. [PMID: 22543409 PMCID: PMC3558031 DOI: 10.1039/c2an35198f] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Single-cell measurements allow a unique glimpse into cell-to-cell heterogeneity; even small changes in selected cells can have a profound impact on an organism's physiology. Here an integrated approach to single-cell chemical sampling and assay are described. Capillary electrophoresis (CE) with laser-induced native fluorescence (LINF) has the sensitivity to characterize natively fluorescent indoles and catechols within individual cells. While the separation and detection approaches are well established, the sampling and injection of individually selected cells requires new approaches. We describe an optimized system that interfaces a single-beam optical trap with CE and multichannel LINF detection. A cell is localized within the trap and then the capillary inlet is positioned near the cell using a computer-controlled micromanipulator. Hydrodynamic injection allows cell lysis to occur within the capillary inlet, followed by the CE separation and LINF detection. The use of multiple emission wavelengths allows improved analyte identification based on differences in analyte fluorescence emission profiles and migration time. The system enables injections of individual rat pinealocytes and quantification of their endogenous indoles, including serotonin, N-acetyl-serotonin, 5-hydroxyindole-3-acetic acid, tryptophol and others. The amounts detected in individual cells incubated in 5-hydroxytryptophan ranged from 10(-14) mol to 10(-16) mol, an order of magnitude higher than observed in untreated pinealocytes.
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Abstract
Cells are extraordinarily complex, containing thousands of different analytes with concentrations spanning at least nine orders of magnitude. Analyzing single cells instead of tissue homogenates provides unique insights into cell-to-cell heterogeneity and aids in distinguishing normal cells from pathological ones. The high sensitivity and low sample consumption of capillary and on-chip electrophoresis, when integrated with fluorescence, electrochemical, and mass spectrometric detection methods, offer an ideal toolset for examining single cells and even subcellular organelles; however, the isolation and loading of such small samples into these devices is challenging. Recent advances have addressed this issue by interfacing a variety of enhanced mechanical, microfluidic, and optical sampling techniques to capillary and on-chip electrophoresis instruments for single-cell analyses.
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