title: TAILS N-terminomics of human platelets reveals pervasive metalloproteinase-dependent proteolytic processing in storage.
abstract: Proteases, and specifically metalloproteinases, have been linked to the loss of platelet function during storage before transfusion, but the underlying mechanisms remain unknown. We used a dedicated N-terminomics technique, iTRAQ terminal amine isotopic labeling of substrates (TAILS), to characterize the human platelet N-terminome, proteome, and posttranslational modifications throughout platelet storage over 9 days under blood-banking conditions. From the identified 2938 proteins and 7503 unique peptides, we characterized N-terminal methionine excision, co- and posttranslational Nα acetylation, protein maturation, and proteolytic processing of proteins in human platelets. We also identified for the first time 10 proteins previously classified by the Human Proteome Organization as "missing" in the human proteome. Most N termini (77%) were internal neo-N termini (105 were novel potential alternative translation start sites, and 2180 represented stable proteolytic products), thus highlighting a prominent yet previously uncharacterized role of proteolytic processing during platelet storage. Protease inhibitor studies revealed metalloproteinases as being primarily responsible for proteolytic processing (as opposed to degradation) during storage. System-wide identification of metalloproteinase and other proteinase substrates and their respective cleavage sites suggests novel mechanisms of the effect of proteases on protein activity and platelet function during storage. All data sets and metadata are available through ProteomeXchange with the data set identifier PXD000906.
authors.affiliation: Centre for Blood Research, and Department of Oral Biological and Medical Sciences, University of British Columbia, Vancouver, BC, Canada;
authors.forename: Anna
authors.initials: A
authors.lastname: Prudova
authors.affiliation: Centre for Blood Research, and Canadian Blood Services, Vancouver, BC, Canada; and.
authors.forename: Katherine
authors.identifier: http://orcid.org/0000-0002-5259-4897
authors.initials: K
authors.lastname: Serrano
authors.affiliation: Centre for Blood Research, and Department of Oral Biological and Medical Sciences, University of British Columbia, Vancouver, BC, Canada;
authors.forename: Ulrich
authors.identifier: http://orcid.org/0000-0001-5863-4514
authors.initials: U
authors.lastname: Eckhard
authors.affiliation: Centre for Blood Research, and Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Nikolaus
authors.identifier: http://orcid.org/0000-0003-4025-9968
authors.initials: N
authors.lastname: Fortelny
authors.affiliation: Centre for Blood Research, and Canadian Blood Services, Vancouver, BC, Canada; and Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Dana V
authors.initials: DV
authors.lastname: Devine
authors.affiliation: Centre for Blood Research, and Department of Oral Biological and Medical Sciences, University of British Columbia, Vancouver, BC, Canada; Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Overall
mesh_terms: D000595:Amino Acid Sequence; D001792:Blood Platelets / Q000378:metabolism*; D001793:Blood Preservation; D001798:Blood Proteins / Q000378:metabolism; D006801:Humans; D007553:Isotope Labeling; D013058:Mass Spectrometry; D045726:Metalloproteases / Q000378:metabolism; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D020543:Proteome; D040901:Proteomics / Q000379:methods*; D013048:Specimen Handling
chemical_list: D001798:Blood Proteins; D020543:Proteome; D045726:Metalloproteases; D010447:Peptide Hydrolases