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Cation‐independent Mannose 6‐Phosphate Receptor Interacts with Several Components of the Plasminogen Activation System
Author(s) -
Bohnsack Richard,
Miller James,
Twining Sally,
Olson Linda,
Dahms Nancy
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.774.5
Subject(s) - mannose 6 phosphate , receptor , chemistry , plasmin , plasminogen activator , kringle domain , mannose , glycan , endosome , biochemistry , lysine , urokinase , urokinase receptor , extracellular , mannose receptor , glycoprotein , enzyme , biology , amino acid , growth factor , endocrinology , macrophage , in vitro , genetics
The 300 kDa cation‐independent mannose 6‐phosphate receptor (CI‐MPR) functions in the biogenesis of lysosomes by trafficking newly synthesized lysosomal enzymes with mannose 6‐phosphate (Man‐6‐P)‐containing glycans to the late endosome. In addition, CI‐MPR binds a number of proteins at the cell surface in a glycan‐independent manner, including plasminogen, urokinase‐type plasminogen activator receptor, and insulin‐like growth factor 2. The ability of CI‐MPR to interact with these different ligands is facilitated by its large extracellular region that is composed of 15 contiguous domains. Previous studies have shown that plasminogen binds to CI‐MPR through one or more of its lysine‐binding kringle domains. We report here that tissue‐type plasminogen activator (tPA), which contains two kringle domains, also binds to CI‐MPR. Using surface plasmon resonance, we demonstrate that tPA binds with high affinity to the N‐terminus of CI‐MPR and that CI‐MPR domain 1 appears to be sufficient for binding. The interaction of tPA with CI‐MPR can be partially inhibited by the lysine analog 6‐aminohexanoic acid and by Man‐6‐P, however, the exact nature of the protein interaction is unknown. Addition of CI‐MPR to tPA and plasminogen enhances the rate of plasmin formation. This rate enhancement shows saturable kinetics for receptor with a K ½ of approximately 120 nM. The rate of enhancement is dependent on more than one domain of the receptor as CI‐MPR domain 1 by itself is not sufficient to enhance tPA‐dependent plasminogen activation. We propose that CI‐MPR acts as a scaffold to bring tPA and plasminogen together and augments conversion of plasminogen to plasmin by tPA. Angiostatin K1‐4 protein, which includes the pan domain and kringles 1‐4 of plasminogen, is able to inhibit the tPA‐dependent activation of plasminogen in the presence of CI‐MPR. Addition of a lysosomal enzyme also inhibits the CI‐MPR enhancement of plasminogen activation by tPA in a concentration‐dependent manner. Characterization of the mechanisms of these inhibitors will help in understanding the interaction of CI‐MPR with tPA and plasminogen along with providing a better understanding of CI‐MPR's ability to interact with multiple ligands. Support or Funding Information Funding: NIH R01DK042667