Dataset Information

Identification and quantification of human postmortem frontal cortex proteome with a SILAM mouse brain standard

ABSTRACT: Prefrontal cortex tissue slices from a cognitively and neurpathologically normal human subject were obtained from the University of Pennsylvania (UPenn) Brain Bank. 300-350 mg grey matter was homogenized in 1.5 ml solution A (0.32 M sucrose, 1mM MgCl2 and 0.1mM CaCl2) with a Teflon pestle. ~100 ?l of the homogenate was saved, solubilized with 1% SDS and clarified by centrifugation. To prepare the [13C6]brain ISTD, 400 mg labeled MouseExpress brain tissue (Cambridge Isotopes, MA) was homogenized in 4 ml buffer A as described above, centrifuged at 1,000 x g for 10 min to clarify, agitated on a rocker at 4�C for 30 min, and centrifuged at 10,000 x g for 20 min. The pellet, a crude membrane fraction, was dissolved in 2 ml 20 mM Tris pH 7.4 with 1% SDS. Total protein in all preparations was quantified with the micro BCA assay (Pierce) and all solutions were supplemented with protease and phosphate inhibitor cocktails (Sigma) as well as 1 mM sodium fluoride and sodium orthovanadate (Sigma). Human cortex homogenate was mixed with the [13C6]brain ISTD (1?g/?l) at a ratio of 2:1(?g/?g) and processed for LC-MS/MS: 40 ?l preparations were heated with lithium dodecyl sulfate (LDS) (Invitrogen) buffer at 95�C for 20 min, separated on a 1.5 mm 4-12% Bis-Tris Gel (Invitrogen), cut into five fractions, chopped into ?2 mm cubes, washed in 200 ?l 50% acetonitrile (ACN) containing 25 mM NH4HCO3, reduced in 300 ?l 10 mM DTT, alkylated in 300 ?l 55 mM iodoacetamide (Sigma), and digested with 80-120 ?l trypsin (.025 ?g/?l) (Promega) overnight at 37�C, so that the amount of trypsin was 1:5 of the total protein to be digested by mass. Peptides were recovered from gel cubes into 200 ?l 50/50 H2O/ACN with 3% formic acid by vortex-mixing and sonication for 20 min each, twice. Samples were then evaporated to a 100 ?l volume, brought to 1ml in H20 with 0.1% formic acid, desalted with Oasis� HLB cartridges (Waters), evaporated almost to completion and suspended in ~ 45?l H2O with 0.1% formic acid, and filtered with 0.22 �m Ultra free-MC filter cartridges (Millipore). LC-data dependant -MS/MS analyses were conducted on a Q Exactive (ThermoFisher Scientific) quadrupole orbi-trap hybrid instrument with an Easy nLC-II (ThermoFisher Scientific) nano-pump/autosampler. 3?l peptide sample (~ 1 ug) was loaded and resolved on a 20 cm x 75 �m proteopepII C18 packed tip column over a 90 min gradient at a flow rate of 350 nL/min, 0-35% mobile phase B (ACN, 0.1 formic acid). A data-dependent top 10 method was used to acquire a 70,000 resolution full scan to trigger ten 17,500 resolution HCD scans. Ions were isolated for MS/MS analysis with a 2.0 Da window on the quadrupole. Average cycle times were 1.2 sec. Each sample was analyzed in triplicate. Raw files from triplicate injections were searched together within Proteome Discoverer 1.3 (ThermoFisher Scientific) using SEQUEST and the human refseq. database (release 47, ftp://ftp.ncbi.nih.gov/refseq/H_sapiens/mRNA_Prot/). Search parameters allowed trypsin to cleave after Lysine and Arginine and have 2 missed cleavages. Precursor ion mass tolerance was set to 15 ppm and fragment ion mass tolerance was 20 mmu. The dynamic modification of methionine (oxidation = 15.995 Da) and lysine (13C6 = 6.020 Da), in addition to the static modification of cysteine (carbamidomethylation = 57.021 Da) was accepted on up to 4 residues per peptide. Within the Proteome Discoverer Software, SILAC pairs were identified using the �2 plex� workflow node, and all peptides were rescored using the Percolator algorithm node. Finally, peptides were filtered at 1% false discovery rate (FDR).

REANALYSED by: PAe005153

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Brain

SUBMITTER: Matthew MacDonald

LAB HEAD: Matthew MacDonald

PROVIDER: PXD000004 | Pride | 2012-12-10

REPOSITORIES: Pride

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Publications

Biochemical fractionation and stable isotope dilution liquid chromatography-mass spectrometry for targeted and microdomain-specific protein quantification in human postmortem brain tissue.

MacDonald Matthew L ML Ciccimaro Eugene E Prakash Amol A Banerjee Anamika A Seeholzer Steven H SH Blair Ian A IA Hahn Chang-Gyu CG

Molecular & cellular proteomics : MCP 20120831 12

Synaptic architecture and its adaptive changes require numerous molecular events that are both highly ordered and complex. A majority of neuropsychiatric illnesses are complex trait disorders, in which multiple etiologic factors converge at the synapse via many signaling pathways. Investigating the protein composition of synaptic microdomains from human patient brain tissues will yield valuable insights into the interactions of risk genes in many disorders. These types of studies in postmortem t ...[more]

PMID: 22942359

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Project description:Female Sprague-Dawley rats were randomly separated into two groups: i) trained (Ex group) and ii) sedentary (Cont group). Animals from the Ex group were adapted to treadmill exercise for two consecutive weeks, involving a gradual increase in the running time till 60 min/day at 20 m/min, 0% grade, 5 days/week. This exercise program remained constant until the end of the 54 weeks. Mitochondria isolation from 10 animals (5 Ex group and 5 Cont group) was performed using the conventional methods of differential centrifugation. Mitochondrial protein extracts were reduced with dithiothreitol, alkylated with iodoacetamide and digested with trypsin using the FASP procedure (18). Briefly, each sample was solubilized in 4 % SDS, 0.1 M DTT, 0.1 M HEPES and incubated for 30 min at 60 C. Then, samples were mixed with 0.2 mL of a solution of 8 M Urea, 0.1 M HEPES, pH 8.5 (UH solution), loaded into the filtration devices (3k Microcon, Millipore), centrifuged at 14,000 g for 20 min, and washed twice with UH solution. After centrifugation, the concentrates were alkylated with 50 mM iodoacetamide in UH solution (dark, 25 C, 20 min), and washed twice with UH solution. The concentrate was diluted with 0.1 mL of 50 mM ammonium bicarbonate (ABC) and digested overnight (37 C) with the addition of 2 ug of trypsin diluted in 30 uL of 50 mM ABC. The resulting tryptic peptides were collected by centrifugation and the filter were washed twice with 50 uL of 50 mM ABC. Eluted peptides were acidified with 10 uL of formic acid and cleaned up on a homemade Empore C18 column (3M, St. Paul, MN, USA) (ref) for subsequent phospho-enrichment and/or analysis by LC-MS/MS. The dried protein digest was dissolved with 10 uL (3 % ACN, 0.1 % TFA), diluted 1:5 with loading buffer (1 M glycolic acid, 5 % TFA, 80 % ACN) and phosphopeptides were enriched on TiO2-beads as previously described (19). Briefly 5 mg of "Titansphere TiO2 5 um" were suspended in 100 uL of 100 % ACN, immobilized in a pipette-column and washed using 5 uL of loading buffer. Each sample was loaded in each pipette-column and then washed with 30 uL of washing buffer (1 % TFA, 80 % ACN). Phosphopeptides were eluted from the beads with 25 uL of 25 % ACN (v/v) containing 25 % NH4OH (m/v), acidified with 10 uL of 10 % TFA and vacuum- concentrated to approximately 4 uL. Samples were finally diluted to 10 uL with H2O + 0.1% formic acid prior to injection. The peptides mixtures were analyzed by online nanoflow liquid chromatography tandem mass spectrometry (nanoLC-MS/MS) on an EASY-nLC system (Proxeon Biosystems, Odense, Denmark) connected to the LTQ Orbitrap Velos instrument (Thermo Fisher Scientific, Bremen, Germany) through a nanoelectrospray ion source. Six microliters of the peptide mixture were auto-sampled directly onto the analytical HPLC column (120 mm x75 um I.D., 3 um particle size (Nikkyo Technos Co., Ltd.) with a 120-min gradient from 5 % to 50 % ACN in 0.1 % FA. The effluent from the HPLC column was directly electrosprayed into the mass spectrometer. The LTQ Orbitrap Velos instrument was operated in data-dependent acquisition mode to automatically switch between full scan MS and MS/MS acquisition. The MS survey scan was performed in the FT cell recording a window between 350 and 2000 m/z. The resolution was set to 60 000, and the automatic gain control was set to 1,000,000 ions with a maximal acquisition time of 400 ms. The 20 most intense peptide ions with charge states great than or equal to 2 were sequentially isolated to a target value of 5,000 and fragmented in the high-pressure linear ion trap by low-energy CID with normalized collision energy of 35% Q value of 0.25, and an activation time of 10 ms. Raw files were processed using Proteome Discoverer version 1.3 (Thermo Fisher Scientific, Bremen). Peak lists were searched using Mascot software version 2.3 (Matrix Science, UK) against a SwissProt database containing entries corresponding to Rattus norvegicus (version of July 2012), a list of common contaminants, and all the corresponding decoy entries. Trypsin was chosen as enzyme and a maximum of two miscleavages were allowed. Carbamidomethylation (C) was set as a fixed modification, whereas oxidation (M) and phosphorylation (STY) were used as variable modifications. Searches were performed using a peptide tolerance of 7 ppm, a product ion tolerance of 0.5 Da. Resulting data files were filtered for FDR less than 1 % at peptide level.

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