THP-1 macrophage membrane-bound plasmin activity is up-regulated by transforming growth factor-beta 1 via increased expression of urokinase and the urokinase receptor. Academic Article uri icon

Overview

abstract

  • Receptors for urokinase (uPA) and plasminogen provide a mechanism to direct the cellular activation of plasminogen. The regulation of these receptors is important for several macrophage functions. In these studies, the effect of transforming growth factor-beta 1 (TGF-beta 1) on uPA, uPA receptor, and plasminogen receptor expression by human THP-1 macrophage was examined. TGF-beta 1 induction of uPA expression by THP-1 cells was differentiation dependent. Suspension and adherent cultures expressed similar constitutive levels of uPA. Exposure of adherent cells to TGF-beta 1 led to a dose- and time-dependent increase in uPA activity which was paralleled by an increase in uPA antigen and uPA mRNA. In contrast, uPA expression by suspension cultures was unresponsive to TGF-beta 1. The differential response exhibited by suspension and adherent THP-1 cells may reflect differences in their expression of TGF-beta 1 receptors, since when assayed by crosslinking techniques, suspension cells primarily expressed a 65 kDa receptor; whereas, the adherent cells expressed 65 and 100 kDa receptors. TGF-beta 1-induced alterations in uPA receptor expression by adherent THP-1 cells were examined by quantitating membrane-bound uPA activity. Membrane-bound uPA activity increased three-fold when cells were incubated with TGF-beta 1. The increase in membrane-uPA activity expressed by TGF-beta 1-treated cells was not due to increased uPA receptor occupancy since incubation of either control or TGF-beta 1 primed cells with exogenous uPA did not lead to an increase in membrane-bound uPA activity. Furthermore, immunoreactive uPA receptor was increased in TGF-beta 1-treated cells. Following incubation with plasminogen, membrane-bound plasmin activity increased three-fold in TGF-beta 1-treated cells. However, no change in immunoreactive membrane-bound plasmin(ogen) was observed. In addition, binding of 125I-Lys-plasminogen to THP-1 cells was not affected by TGF-beta 1 treatment. We conclude that TGF-beta 1 stimulates membrane-bound plasmin activity, without affecting plasminogen receptor expression, through the up-regulation of uPA and the uPA receptor expression.

publication date

  • August 1, 1995

Research

keywords

  • Fibrinolysin
  • Macrophages
  • Receptors, Cell Surface
  • Transforming Growth Factor beta
  • Urokinase-Type Plasminogen Activator

Identity

Scopus Document Identifier

  • 0029093245

Digital Object Identifier (DOI)

  • 10.1002/jcp.1041640214

PubMed ID

  • 7622580

Additional Document Info

volume

  • 164

issue

  • 2