Role of Sphingolipid- and Cholesterol-Rich Membrane Domains in Pathophysiology of Cultured Human Breast Cancer Cells

摘要

UPAR (urokinase-type plasminogen activator receptor) is a key player in metastasis of breast cancer cells. We suggest that uPAR, because it is a GPI- anchored protein, must be present in discrete 'rafts' in the cell surface to function. Our proposal has two parts. First, we will set up systems in our lab for studying signaling through uPAR in cultured human breast cancer cells. Second, we will disrupt rafts, and determine whether signal transduction is affected. Our most important advance this year has been in developing tools for monitoring raft disruption. Agents that remove cholesterol from membranes (such as methyl-beta-cyclodextrin) or that sequester cholesterol within the membrane (such as filipin) can disrupt rafts. We have shown that these agents strongly inhibit normal raft-dependent clustering of raft proteins and lipids in the plasma membrane, and that this inhibition is easily detectable by fluorescence microscopy. This will be an important tool in later experiments to examine the effect of raft disruption on uPAR-mediated signaling and cell motility. We anticipate in the next year, we will develop improved methods for detecting uPAR in rafts in cells. We will then determine how the localization of uPAR in rafts governs its deadly activity in metastasis.