Streptococcus sanguinis and the sera of patients with Behçet’s disease stimulate membrane expression of α-enolase in human dermal microvascular endothelial cells

Abstract

The glycolytic enzyme α-enolase is a plasminogen-binding protein that is generally found in the cytosolic compartment. However, α-enolase can also be expressed on cell surfaces following an inflammatory stimulus via an unknown mechanism. We investigated the effects ofStreptococcussanguinis(S.sanguinis) and theseraofpatientswith Behçet'sdisease(BD) on theexpressionand distribution of α-enolase inhumandermalmicrovascularendothelialcells(HDMECs). HDMECs were stimulated with cultured S.sanguinisand theseraof active BDpatients. HDMECs incubated for 6, 12 or 24h were harvested, and themembraneand cytoplasmic fractions of proteins were extracted. Theexpressionand distribution of α-enolase were analyzed using subcellular fractionation and immunoblotting. Subcellular localization of α-enolase was also assessed by immunocytochemistry. S.sanguinisstimulated theexpressionof α-enolase in the membranous compartment of HDMECs in a dose-dependent manner. This pattern was also observed in HDMECs incubated with BDpatients'sera. Although incubation of HDMECs withserafrom healthy controls increasedmembraneexpressionof α-enolase, incubation with BDseraresulted in earlier and higherexpressionof this glycoprotein in the cellularmembraneof HDMECs. Immunocytochemistry revealed strong immunostaining of α-enolase in the cytoplasm and cytoplasmicmembraneof HDMECs incubated with S.sanguinisor BDpatients'sera. In conclusions, these results indicate that S.sanguinisinfection and theseraof BDpatientswith activediseaseare inflammatory stimuli that can induce membranous α-enolaseexpressioninendothelialcells.Membrane-expressed α-enolase could potentially react with anti-α-enolase antibodies in BDpatients'sera, resulting in increased inflammation.