Pervanadate-induced shedding of the intercellular adhesion molecule (ICAM)-1 ectodomain is mediated by membrane type-1 matrix metalloproteinase (MT1-MMP)

In several vascular diseases, the ectodomain of intercellular adhesion molecule (ICAM)-1 is shed by the proteolytic activity of a zinc-dependent endopeptidase, releasing a soluble form of the protein (sICAM-1), a common marker for inflammatory diseases. Since reactive oxygen species (ROS) generated during prolonged inflammation are known to induce shedding or cleavage of several transmembrane proteins, we sought to explore the cleavage and enzymatic effects that the pervanadate, via oxidation and subsequent inactivation of protein tyrosine phosphatase, has on ICAM-1 cleavage. In these studies, we used endothelial cells (ECs) and 293 human embryonic kidney (HEK) cells expressing high-levels of surface ICAM-1. In addition, use of specific tissue inhibitors of metalloproteinases (TIMPs), small interfering (si)RNA designed to knockdown endopeptidase activity, and an immunocolocalization assay were employed to determine the identity of a specific metalloproteinase mediating pervanadate-induced sICAM-1 shedding. Our data indicate that membrane type-1 matrix metalloproteinase (MT1-MMP) is involved in pervanadate-mediated shedding of the sICAM-1 ectodomain in both cell types. Immunostaining and confocal microscopy provide visual evidence that ICAM-1 and MT1-MMP colocalize at the cellular surface following pervanadate treatment, further implicating the involvement of MT1-MMP activity in this mode of ICAM-1 shedding.