Figure 8.

PP2A is responsible for histamine-stimulated eNOS dephosphorylation. HUVECs were maintained at 18% O₂ or cultured in 10, 5, 3, or 1% O₂ for at least 5 d. A) Representative immunoblot and densitometric analysis of PP2A-C expression relative to β-actin. B) Analysis of PP2A subcellular distribution in response to histamine stimulation (10 µM, 5 min) using immunofluorescence and ultracentrifugation (Supplemental Fig. S4). DAPI costaining not shown for clarity. C, D) Colocalization of eNOS and PP2A-C assessed by coimmunoprecipitation (C) and proximity ligation assay (D). Red dots indicate physical protein interaction. The total number of cells is indicated above each frequency distribution; data are means ± sem. PLA signals per cell shown in the inset. All other data represent means ± sem from 3 to 9 different donors. *P < 0.05, **P < 0.01 vs. 18% O₂; ⁺P < 0.05 vs. vehicle.