The extracellular matrix (ECM) plays an important regulatory role in cell shape determination, adhesivity, growth control and differentiation. Excessive ECM accumulation occurs in several clinically important fibroproliferative diseases leading to loss of normal tissue architecture, defects in cellular growth control and impaired organ function. To clarify how these events are related, with reference to the biology of fibrotic disorders, our studies have focused on a specific ECM-associated 32-kDa glycoprotein (p52) the expression of which is greatly elevated in fibroproliferative diseases involving the orbit, lungs, liver, and kidneys. We have recently identified p52 as plasminogen activator inhibitor type-1 (PAI-1), a potential determinant of the pericellular proteolytic environment and of ECM organization/stability. Our long-term goals are to determine the function of p52(PAI-1) in kidney cell growth control, to ascertain its role in the etiology of renal fibrosis and to identify specific molecular mechanisms underlying growth factor/ECM- mediated regulation of p32(PAI-1) gene expression in renal cells. These studies will lead to the development of new clinical strategies focusing on use of the p52(PAI-1) gene and its regulatory network as therapeutic """"""""targets"""""""" in the treatment of fibroproliferative disorders. We hypothesize that (a) structural elements of the ECM, either directly or through changes in cell shape, transduce specific signals which regulate p52(PAI- 1) gene expression, (b)ECM-associated p52(PAI-1) is a key determinant in renal cell substrate adhesion and growth control and (c) modulation of p52(PAI-1) expression results in disease-related changes in renal cell growth traits. To evaluate these hypotheses, the following specific aims will be addressed: 1. We will define specific molecular mechanisms whereby p52(PAI-1) gene expression in renal cells is positively regulated by components of the ECM focusing, in particular, on structural elements of the ECM implicated in renal fibroproliferative disease. 2. We will identify specific genetic elements in renal cells which function to regulate p32(PAI-1) gene expression in the ECM-dependent inductive pathway and determine whether they are the same or different from sequences involved in growth factor- and cell shape-dependent gene control. 3. We will utilize our recently prepared panel of genetically engineered renal cells, designed to over- and under-express p52(PAI-1) specifically, to define the consequences of p32(PAI-1) expression perturbation on renal cell growth traits and their phenotypic response to factors implicated in renal fibroproliferative disorders. 4. We will evaluate the usefulness of directed molecular and chemotherapeutic agents to target the p52(PAI-1) gene and down regulate p52(PAI-1) expression using both in vitro and in vivo models of renal fibrotic disease.
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