title: Refined phosphopeptide enrichment by phosphate additive and the analysis of human brain phosphoproteome.
abstract: Alzheimer's disease (AD) is the most common form of dementia, characterized by progressive loss of cognitive function. One of the pathological hallmarks of AD is the formation of neurofibrillary tangles composed of abnormally hyperphosphorylated tau protein, but global deregulation of protein phosphorylation in AD is not well analyzed. Here, we report a pilot investigation of AD phosphoproteome by titanium dioxide enrichment coupled with high resolution LC-MS/MS. During the optimization of the enrichment method, we found that phosphate ion at a low concentration (e.g. 1 mM) worked efficiently as a nonphosphopeptide competitor to reduce background. The procedure was further tuned with respect to peptide-to-bead ratio, phosphopeptide recovery, and purity. Using this refined method and 9 h LC-MS/MS, we analyzed phosphoproteome in one milligram of digested AD brain lysate, identifying 5243 phosphopeptides containing 3715 nonredundant phosphosites on 1455 proteins, including 31 phosphosites on the tau protein. This modified enrichment method is simple and highly efficient. The AD case study demonstrates its feasibility of dissecting phosphoproteome in a limited amount of postmortem human brain. All MS data have been deposited in the ProteomeXchange with identifier PXD001180 (http://proteomecentral.proteomexchange.org/dataset/PXD001180).
authors.affiliation: St. Jude Proteomics Facility, St. Jude Children's Research Hospital, Memphis, TN, USA.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Tan
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Wu
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
authors.forename: Bing
authors.initials: B
authors.lastname: Bai
authors.forename: Yuxin
authors.initials: Y
authors.lastname: Li
authors.forename: Xusheng
authors.initials: X
authors.lastname: Wang
authors.forename: Bo
authors.initials: B
authors.lastname: Zhai
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Beach
authors.forename: Junmin
authors.initials: J
authors.lastname: Peng
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism; D000595:Amino Acid Sequence; D001921:Brain / Q000378:metabolism; D001923:Brain Chemistry; D002853:Chromatography, Liquid / Q000379:methods; D006801:Humans; D008969:Molecular Sequence Data; D010710:Phosphates / Q000737:chemistry; D010748:Phosphopeptides / Q000032:analysis* / Q000302:isolation & purification / Q000378:metabolism; D010766:Phosphorylation; D020543:Proteome / Q000737:chemistry* / Q000378:metabolism; D040901:Proteomics / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods; D014025:Titanium / Q000737:chemistry
chemical_list: D010710:Phosphates; D010748:Phosphopeptides; D020543:Proteome; C009495:titanium dioxide; D014025:Titanium
keywords: Alzheimer's disease; Human brain; LC-MS/MS; Phosphopeptide enrichment; Phosphorylation; Technology