College of Pharmacy

Research

Phospholipase C-ß (PLC-ß) isoenzymes are a family of intracellular signaling molecules that are activated in cells in numerous normal and pathophysiological processes; for example, activation of PLC-ß enzymes leads to smooth muscle cell contraction and may stimulate smooth muscle cell hypertrophy and chronic hypertension. PLC-ß activation is also associated with post-ischemic cardiac remodeling, premature uterine hyperexcitability, neuronal excitability and malignant transformation of certain cell types (small cell lung cancer cells, among others). Drug therapies targeted at inhibition or desensitization of PLC-ß isoenzymes may be useful in the treatment or prevention of cardiac remodeling, hypertension, premature labor, certain cancers and/or manic-depressive illness. To intervene effectively in pathological processes associated with PLC-ß activation, we must identify cell-specific protein targets that regulate PLC-ß enzyme activity and can be acted upon pharmacologically in a way that will spare normal processes. To design PLC-ß-based therapies we must know more about the means of intracellular control of PLC-ß activity. The goal of Theresa Filtz’s laboratory is to understand the multiple, cell-specific means by which PLC-ß enzymes are regulated.

PLC-ß isoenzymes function by hydrolyzing membrane lipids and are primarily activated by receptors linked to membrane-bound G proteins. Further regulation of PLC-ß isoenzymes may be mediated by other proteins that phosphorylate PLC-ß isoenzymes to inhibit activity, that control of PLC-ß access to its membrane-bound substrate, or that modulate co-factors such as Ca++. Filtz's laboratory is studying PLC-ß3 isoenzyme regulation by kinases, lipid binding proteins and Ca++ regulatory proteins. They utilize well-defined kinetics assays to study phosphorylation-mediated inhibition of PLC-ß hydrolytic activity in vitro. The lab has human aortic smooth muscle cells and brain-derived human astrocytoma cells growing in culture in which to study the regulation of PLC-ß activity in vivo. With the recent purchase by the pharmacology group in the College of Pharmacy of a high-sensitivity fluorescence microscope with computerized 3-D reconstructive capabilities, they have begun to use fluorescence microscopy as a means of studying the membrane binding properties and subcellular localization of PLC-ß molecules to further associate access to substrate with the regulation of PLC-ß activity in vivo. Additionally, using a yeast-based assay system, the lab has identified a few proteins, besides G proteins and kinases, that associate with PLC-ß3. They have begun to study the function of these associated proteins on PLC-ß activity.