Abstract
BackgroundSatisfactory sample preparation for mass spectrometry-based analysis is a critical step in the proteomics workflow. The quality and reproducibility of sample preparation can determine the coverage and confidence of proteomics results. Up to date, several methodologies have been described to produce suitable peptides for mass spectrometry analysis, followed by strategies for enrichment of post-translational modified peptides, if desired. Among them, the filter-aided sample preparation (FASP) has been introduced as a method to allow for removal of denaturants, reductants, alkylators, lipids and nucleic acids prior to trypsin digestion. Despite the high proteolytic digestion and contaminant removal efficiency described for this method, filter failure and consequently complete sample loss can discourage the use of this approach by the proteomic community.ResultsAs judged by our quality controls, we were able to perform reliable and reproducible FASP for mass spectrometry analysis that allowed the quantification of 2141 proteins and 3694 phosphopeptides from as little as 20 and 320 μg of protein lysate from acute myeloid leukemia (AML) patients, respectively. Using the immobilized metal ion affinity chromatography (IMAC) method resulted in samples specifically enriched in phosphopeptides and allowed the quantification of a high number of both di- and multi-phosphopeptides in addition to the abundant mono-phosphopeptides. The workflows’ high reproducibility from three biological replicates was demonstrated by the similar number of quantified proteins and localized phosphosites, and confirmed by the similar distributions of their molecular functions. We found that the combination of the FASP procedure with StageTip mixed-mode fractionation and IMAC are excellent workflows for the reproducible and deep study of AML proteomes and phosphoproteomes, respectively.ConclusionsThe FASP procedure can be carried out without the risk of filter failure by performing a simple test of the filter quality before adding the protein sample. Herein, we demonstrate an efficient and reproducible FASP-based pipeline for the proteomic and phosphoproteomic analysis of AML patient samples which also can be used for the analysis of any other protein samples.Electronic supplementary materialThe online version of this article (doi:10.1186/s12575-016-0043-0) contains supplementary material, which is available to authorized users.
Highlights
Satisfactory sample preparation for mass spectrometry-based analysis is a critical step in the proteomics workflow
We found that the filter performance test was a crucial step in our filter-aided sample preparation (FASP) workflow as faulty filters only recovered 0–1 μg of peptides according to absorbance measurements at 280 nm
Proteome of acute myeloid leukemia (AML) patient samples The analysis of three AML patient samples processed with the FASP procedure and styrenedivinylbenzene reverse-phase sulfonate (SDB-RPS) fractionation resulted in 2299, 2191 and 1933 SILAC-quantified protein groups of which more than 94 % were quantified with more than one peptide in all three samples (Fig. 2a)
Summary
Satisfactory sample preparation for mass spectrometry-based analysis is a critical step in the proteomics workflow. Even though the genotypic classification and cytogenetic analyses (e.g. PML-RARA fusion protein) are important for prognostication and identification of possible therapeutic targets, more recent studies have suggested that analysis of cancer phenotypes could contribute with information on both prognosis and new therapies in human malignancies [3, 4], including AML [5]. Proteomic profiling from liquid chromatography-mass spectrometry (LC-MS)-based analyses will be important for our understanding of the molecular mechanisms leading from genetic abnormalities to leukemic transformation, for the identification of new prognostic biomarkers and therapeutic targets that could improve the efficacy of antileukemic treatments in a near future. It is crucial to prepare AML samples for MS analysis according to proteomic and phosphoproteomic methodologies that minimizes proteolytic degradation and allow high protein and phosphorylation coverage
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