The Role of PKCzeta on MT1-MMP Expression with Shear Stress and Cyclic Strain in Microvascular Endothelial Cells

ABSTRACT

PURPOSE: hear stress (SS) and cyclic strain (CS) influence the expression of membrane type 1-matrix metalloproteinase (MT1-MMP) in microvascular endothelial cells (MVECs). It is known that changes in the level of Sp1 phosphorylation are important for MT1-MMP expression following SS and CS. However, the exact mechanism underlying this process is poorly understood. The aim of this study was to determine the effect of PKCzeta on serine phosphorylation and activation of Sp1 in response to SS and CS. METHOD: MVECs were exposed to SS or CS for up to 8 hours with or without PKCzeta inhibitors. The activity and phosphorylation of Sp1 were assessed by Western blot analysis and immunoprecipitation. MT1-MMP protein expression was assessed by Western blot analysis. RESULT: PKCzeta was phosphorylated and activated under SS, whereas no significant changes were noted under CS. SS increased Sp1 phosphorylation in a time-dependent manner, but no changes in the Sp1 phosphorylation were observed when the MVECs were pretreated with the PKCzeta inhibitors. By contrast, MVECs exposed to CS in the presence or absence of PKCzeta inhibitors showed no change in the phosphorylation of Sp1. SS decreased MT1-MMP protein expression in a time-dependent manner, but in the presence of PKCzeta inhibitors, MT1-MMP expression was not changed compared with the static levels after SS. CS increases MT1-MMP expression in a time-dependent manner. Similar expression was observed when the cells were pretreated with PKCzeta inhibitors under CS. CONCLUSION: These data demonstrate that the increased affinity of Sp1 for the MT1-MMP's promoter site occurs because of PKCzeta induced phosphorylation of Sp1 in response to SS.