Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Genetics, Development and Cell Biology

First Advisor

Marit Nilsen-Hamilton


The main goal of this project was to understand the signal transduction pathways through which growth modulators such as TGF-[beta], PMA and retinoic acid mediate protein expression and DNA synthesis. Transforming growth factor [beta] (TGF-[beta]) induces synthesis and secretion of a 48,000 M r protein that we have found to be type I plasminogen activator inhibitor (PAI-1). TGF-[beta] induces PAI-1 in every cell line that we have studied including near term mink lung epithelial CCL64 cells, mouse embryo fibroblast AKR-2B 84A cells, African green monkey kidney epithelial BSC-1 cells, and normal rat kidney fibroblast NRK 49F cells. PAI-1 is induced synergistically by TGF-[beta] and EGF in CCL64 cells. Phorbol 12-myristate 13-acetate induces PAI-1 in CCL64, BSC-1 and NRK cells but not in AKR-2B cells. TGF-[beta] and retinoic acid both induce synthesis and secretion of a 73,000 M r protein by CCL64 cells that we call inhibitor-induced protein, 73 kDa (IIP73). Retinoic acid does not significantly regulate PAI-1 expression. PMA does not induce IIP73. To test whether cAMP was a regulator of the growth modulator effects, we treated cells with agents which increase intracellular cAMP (forskolin, cholera toxin, and dibutyryl cAMP) and measured the effects on expression of PAI-1 and IIP73 and on DNA synthesis. We found that agents that increase intracellular cAMP lowered the basal and induced levels of PAI-1 coordinately and lowered DNA synthesis rates in AKR-2B, BSC-1, CCL64 and NRK cells. However, these same factors had little or no effect on the ability of TGF-[beta] or retinoic acid to induce IIP73. To test for the necessity of activated protein kinase C (PKC) in the induction of PAI-1 and IIP73 expression and to test the role of PKC in stimulation of DNA synthesis, we down-regulated PKC in CCL64 cells by a 48 h incubation with a high concentration of PMA. While PMA could no longer induce PAI-1, there was no effect on the ability of TGF-[beta] to induce PAI-1 and no effect on the ability of TGF-[beta] and retinoic acid to induce IIP73. However, down-regulation of PKC prevented retinoic acid stimulation of DNA synthesis in CCL64 cells. This shows that induction of PAI-1 by TGF-[beta] does not depend on activation of PKC and that retinoic acid may induce proliferation in CCL64 cells through a PKC-dependent mechanism.



Digital Repository @ Iowa State University,

Copyright Owner

Frederic William Thalacker



Proquest ID


File Format


File Size

143 pages