Since the discovery that specific polypeptide factors termed transforming growth factors (TGFs) were able to confer the transformed phenotype to otherwise normal cells, elucidation of their mechanisms of action has been a goal in cancer research. Over the past few years a great deal of effort has been expended in the isolation and purification of TGFs, since mechanistic studies require the use of purified molecules. Recently, highly purified preparations of TGFs (TGF-alpha and TGF-beta) have been obtained, thereby paving the way for attempts to determine their mechanisms of action and the set of specific cellular responses which they elicit. This research intends to address questions regarding the identity of specific cell-surface TGF receptors, their involvement in mediating TGF-associated responses, and the specific intracellular consequences of TGF action. Efforts will continue to purify TGF-alpha and TGF-beta from rat fetuses, utilizing chromatography, isoelectric focusing, and HPLC methods. Purified TGFs will be iodinated in order to elucidate their characteristics of binding to cell surfaces of nontransformed and transformed mouse and rat cells. The characteristics of endocytosis and intracellular processing of ?125?I-TGFs will be investigated, with emphasis on intracellular sites of TGF processing. Photoaffinity labeling of TGF receptors will be employed to demonstrate their molecular weight characteristics and to determine the intracellular localization of GF-receptor complexes. Clones of cDNAs homologous to genes induced by TGF-alpha and TGF-beta in mouse and rat cells will be obtained in plasmid and phage vectors. These cDNA clones will be employed to determine whether TGF-alpha and TGF-beta induce the same or different gene products and if EGF- and TGF-alpha induce similar gene products. The ability of the tumor promoter TPA to induce gene products similar to those induced by TGFs will also be determined. The endogenous level of expression of TGF-induced genes in transformed cells will be compared to the level found in normal cells. Finally, the ability of lysosomotropic agents to inhibit TGF-induced expression of specific gene products will be investigated. (J)
| Machida, C M; Muldoon, L L; Rodland, K D et al. (1988) Transcriptional modulation of transin gene expression by epidermal growth factor and transforming growth factor beta. Mol Cell Biol 8:2479-83 |
| Muldoon, L L; Rodland, K D; Magun, B E (1988) Transforming growth factor beta modulates epidermal growth factor-induced phosphoinositide metabolism and intracellular calcium levels. J Biol Chem 263:5030-3 |
| Rodland, K D; Jue, S F; Magun, B E (1986) Regulation of VL30 gene expression by activators of protein kinase C. J Biol Chem 261:5029-33 |
