title: Finding the same needles in the haystack? A comparison of phosphotyrosine peptides enriched by immuno-affinity precipitation and metal-based affinity chromatography.
abstract: Analysis of tyrosine (Tyr) phosphorylation by mass spectrometry (MS)-based proteomics remains challenging, due to the low occurrence of this post-translational modification compared to serine and threonine phosphorylation events in mammalian systems. Conventional metal-based affinity chromatography methods used to enrich phosphopeptides can nowadays isolate over 10,000 phosphopeptides. However, these approaches are not particularly suitable for the selective enrichment of low abundant Tyr phosphorylated peptides as the higher abundant co-enriched serine (Ser) and threonine (Thr) phosphorylated peptides typically obscure their detection. Therefore, a more targeted approach based on immuno-affinity precipitation at the peptide level has been introduced for the specific analysis of Tyr phosphorylated species. This method typically leads to the detection of a few hundreds of phosphopeptides, albeit typically over 70% of those are Tyr phosphorylated. Here, we evaluated and compared phosphotyrosine peptides enriched by a phospho-Tyr immuno-affinity enrichment (employing pY99 antibodies) and a multidimensional approach consisting of metal-affinity based enrichment (Ti(4+)-IMAC) followed by hydrophilic interaction liquid chromatography (HILIC) fractionation. Our aim was to assess differences and similarities in the set of Tyr phosphorylated peptides detected by each approach. Our data suggest that both strategies are not redundant but complementary and should ideally be combined for a more comprehensive view at phosphotyrosine signaling.
  
  
  CONCLUSIONS
  Here we evaluated enabling tools for the global analysis of phosphotyrosine phosphorylation. Phosphotyrosine phosphorylation is a key protein modification driving cellular response also involved in disease/cancer molecular pathways.
authors.affiliation: Biomolecular Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Padualaan 8, 3584 CH Utrecht, The Netherlands; Netherlands Proteomics Center, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Serena
authors.initials: S
authors.lastname: Di Palma
authors.forename: Adja
authors.initials: A
authors.lastname: Zoumaro-Djayoon
authors.forename: Mao
authors.initials: M
authors.lastname: Peng
authors.forename: Harm
authors.initials: H
authors.lastname: Post
authors.forename: Christian
authors.initials: C
authors.lastname: Preisinger
authors.forename: Javier
authors.initials: J
authors.lastname: Munoz
authors.forename: Albert J R
authors.initials: AJ
authors.lastname: Heck
mesh_terms: D002846:Chromatography, Affinity / Q000379:methods*; D002853:Chromatography, Liquid; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation / Q000379:methods*; D020014:K562 Cells; D008670:Metals / Q000737:chemistry; D010455:Peptides / Q000737:chemistry*; D010748:Phosphopeptides / Q000737:chemistry; D010750:Phosphoproteins / Q000737:chemistry; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000737:chemistry*; D011499:Protein Processing, Post-Translational; D040901:Proteomics; D015398:Signal Transduction; D014443:Tyrosine / Q000737:chemistry
chemical_list: D008670:Metals; D010455:Peptides; D010748:Phosphopeptides; D010750:Phosphoproteins; D019000:Phosphotyrosine; D014443:Tyrosine
keywords: Hela cells; Immuno-affinity enrichment; K562 cells; Phosphoproteomics; Ti(4+)-IMAC; Tyrosine phosphorylation