Expression of tissue factor procoagulant activity: Regulation by cytosolic calcium

R. Bach, D. B. Rifkin

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193 Scopus citations


Intact bovine fibroblasts, pericytes, and kidney cells manifested significantly less tissue factor procoagulant activity than their disrupted counterparts. Addition of calcium ionophore A23187 rapidly and reversibly enhanced the cell-surface expression of tissue factor in intact cells up to the level achieved by disruption. Inhibitors of calmodulin blocked the ionophore-dependent enhancement of procoagulant activity. Similar kinetic parameters were obtained for factor X hydrolysis by tissue factor-factor VIIa on unperturbed pericytes and phosphatidylcholine vesicles. Increase in V(max) and decrease in apparent K(m) for this reaction were seen after either disruption or ionophore stimulation of the pericytes. Addition of phosphatidylserine to the reconstituted phospholipid vesicles also increased the V(max) and decreased the apparent K(m) for factor X hydrolysis. These data agree with the hypothesis that the expression of tissue factor procoagulant activity on cell surfaces is modulated by calcium-mediated changes in the asymmetric distribution of phosphatidylserine in plasma membrane.

Original languageEnglish (US)
Pages (from-to)6995-6999
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number18
StatePublished - 1990
Externally publishedYes


  • A23187 calmodulin
  • blood coagulation
  • membrane protein
  • phospholipid asymmetry


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