Plasminogen proteoform profiling
Ontology highlight
ABSTRACT: Plasminogen, the zymogen of plasmin, is a glycoprotein involved in fibrinolysis and a wide variety of other physiological processes. Plasminogen dysregulation has been implicated in a range of diseases. Classically, human plasminogen is categorized into two types based on the presence (type I) or absence (type II) of a single N-linked glycan, supposedly having different functional features. Using high-resolution native mass spectrometry (native MS), we uncover that the proteoform profiles of plasminogen (and plasmin) are substantially more extensive than this simple binary classification. In samples derived from human plasma, we identified up to 14 distinct proteoforms of human plasminogen, including a novel, highly abundant phosphorylation site at Ser339. To elucidate potential functional effects of these post-translational modifications, we performed proteoform-resolved kinetic analyses of the plasminogen-to-plasmin conversion using a canonical activator. This conversion is thought to involve at least two independent cleavage events: one to remove the N-terminal peptide, and another to form the active catalytic site. Our analyses reveal that these processes are not independent but are instead tightly regulated and occur in a step-wise order. Notably, N-terminal cleavage at the canonical site (Lys77) does not occur directly from intact plasminogen. Instead, an activation intermediate corresponding to cleavage at Arg68 is initially produced, which only then is further processed to the canonical Lys77 product. Based on our results, we propose a new categorization system for human plasminogen isoforms. This work highlights the capacity of high-resolution native MS to reveal new aspects of structure, even in frequently-studied serum glycoproteins.
INSTRUMENT(S): TripleTOF 5600, Orbitrap Fusion, Q Exactive Plus
ORGANISM(S): Rattus Norvegicus (rat) Homo Sapiens (human)
TISSUE(S): Blood Plasma, Blood Serum
SUBMITTER:
Dario Cramer
LAB HEAD: Albert J. R. Heck
PROVIDER: PXD042225 | Pride | 2024-05-24
REPOSITORIES: pride
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