p38α phosphorylates serine 258 within the cytoplasmic domain of tissue factor and prevents its incorporation into cell-derived microparticles

► The kinase that phosphorylates Ser258 within TF is identified as p38α ► The reaction rate increases by 10 fold on previous phosphorylation of Ser253 in TF ► This arises as a result of exposure of Ser258 following phosphorylation of Ser253 ► The activation of p38 may occur by the retention of TF within activated cells ► A mechanism for the regulation of the release of TF into microparticles is proposed