Binding and endocytosis of alpha 2-macroglobulin-plasmin complexes.

Published

Journal Article

The clearance of 125I-labeled alpha 2-macroglobulin-plasmin complexes (125I-alpha 2M-PM) from mouse circulation is slower than that of 125I-labeled alpha 2M-methylamine complexes (125I-alpha 2M-CH3NH2). In addition, clearance of 125I-alpha 2M-PM is biphasic, but that of 125I-alpha 2M-CH3NH2 follows simple first-order kinetics. Treatment of alpha 2M-PM with trypsin yields a complex that clears like alpha 2M-CH3NH2. Complexes of alpha 2M with Val442-plasmin (alpha 2M-Val442-PM) were prepared; alpha 2M-Val442-PM has a stoichiometry of 2 mol of Val442-PM to 1 mol of alpha 2M and also clears like alpha 2M-CH3NH2. In vitro 4 degrees C binding inhibition studies with mouse peritoneal macrophages show that alpha 2M-CH3NH2, alpha 2M-PM, trypsin-treated alpha 2M-PM, and alpha 2M-Val442-PM bind with the same affinity, apparent Kd = 0.4 nM. The binding isotherms at 4 degrees C are the same for 125I-alpha 2M-CH3NH2, 125I-alpha 2M-PM, and 125I-trypsin-treated alpha 2M-PM in both mouse peritoneal macrophages and 3T3-L1 fibroblasts. The Scatchard plots for the binding isotherms in macrophages were curved; those in 3T3-L1 fibroblasts were linear with an apparent Kd of 0.48 nM and a receptor activity of 140 fmol/mg of cell protein for alpha 2M-CH3NH2, an apparent Kd of 0.29 nM and a receptor activity of 110 fmol/mg of cell protein for alpha 2M-PM, and an apparent Kd of 0.35 nM and a receptor activity of 210 fmol/mg of cell protein for trypsin-treated alpha 2M-PM.(ABSTRACT TRUNCATED AT 250 WORDS)

Full Text

Duke Authors

Cited Authors

  • Ney, KA; Gidwitz, S; Pizzo, SV

Published Date

  • August 13, 1985

Published In

Volume / Issue

  • 24 / 17

Start / End Page

  • 4586 - 4592

PubMed ID

  • 2415157

Pubmed Central ID

  • 2415157

International Standard Serial Number (ISSN)

  • 0006-2960

Digital Object Identifier (DOI)

  • 10.1021/bi00338a016

Language

  • eng

Conference Location

  • United States