Regulation of mesangial cell adhesion and shape by thrombin

W. F. Glass, E. Rampt, J. A. Garoni, J. W. Fenton, J. I. Kreisberg

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Adenosine 3',5'-cyclic monophosphate (cAMP) elevation in cultured rat mesangial cells causes urokinase-dependent adhesion loss, stress-fiber fragmentation, and shape change. Thrombin cleaves single-chain urokinase (scu-PA), causing its inactivation, but not two-chain u-PA [tcu-plasminogen activator (PA)] or tissue-type PA. We tested the ability of thrombin to inhibit the effects of cAMP elevation in mesangial cells and inactivate cell-associated scu-PA. In an assay of trypsin-sensitive adhesion, 65.9% of control cells and 5.5% of cells treated with isoproterenol + methylisobutylxanthine (IM) remained adherent. In the presence of 0.01, 0.1, 1.0, and 10.0 unit/ml thrombin, 20.9, 46.6, 50.4, and 53.3%, respectively, of IM-treated cells remained attached. Thrombin also inhibited stress-fiber fragmentation and shape change. The effects of thrombin were blocked by hirudin or antithrombin III plus heparin. Direct zymography in gels containing gelatin and plasminogen revealed loss of a closely spaced pair of PA bands with thrombin treatment (1.0 unit/ml). Hirudin blocked the loss. α-Thrombin inactivated by diisopropyl fluorophosphate neither inhibited shape change nor caused loss of the PA bands; however, γ-thrombin was nearly as active as native α-thrombin in both regards. Pretreatment of the cells with as little as 1.0 unit/ml thrombin for 1.0 min caused marked inhibition of shape change and near total loss of the slower migrating u-PA band (of the doublet). The faster migrating band was inhibited less. The results indicate that the slower migrating band represents scu-PA; the nature of the faster migrating band is less certain. Thrombin reversed the adhesion loss and shape change caused by 8-(4-chlorophenylthio)-cAMP and MIX. Thus physiological concentrations of thrombin rapidly inactivate mesangial cell scu-PA and inhibit and reverse cAMP-stimulated adhesion loss and shape change. Although inhibition of urokinase-dependent hydrolysis of extracellular matrix protein is apparently one mechanism by which thrombin regulates mesangial cell shape and adhesion, these observations are consistent with the possibility that cleavage of receptor-bound scu-PA by thrombin regulates these processes through signal transduction as well.

Original languageEnglish (US)
Pages (from-to)F336-F344
JournalAmerican Journal of Physiology - Renal Fluid and Electrolyte Physiology
Volume261
Issue number2 30-2
DOIs
StatePublished - 1991
Externally publishedYes

Keywords

  • Adenosine 3',5'-cyclic monophosphate
  • Single-chain urokinase
  • Smooth muscle cell
  • Stress fibers
  • Urokinase

ASJC Scopus subject areas

  • Physiology

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