• Magun, Bruce (PI)

Project: Research project

Project Details


Little is known about the cellular mechanisms by which
transforming growth factor beta (TGF-beta) is able to regulate
the activities of nontransformed and neoplastic cells. Elucidation
of the intracellular pathways of signal transduction should
account for the wide variety of biological responses elicited by
TGF-beta including both stimulatory actions such as the induction
of anchorage-independent growth and neoplastic-like behavior in
some types of cells and the inhibition of growth in other cell
types. Studies from this laboratory have recently established that
TGF-beta, when added in serum-free medium to quiescent Rat-1
cells, will induce a large increase in inositol phosphate generation
several hours later, and will dramatically sensitize the cells to the
IP3-generating effects of EGF, which normally causes only a
feeble increase in inositol phosphate levels. Concomitant with the
increase in IP3 levels produced by EGF in TGF-beta-sensitized
cells is an increase in the levels of free intracellular calcium, as
determined by fura-2 microspectrafluorometry. In a similar time
frame as phosphoinositide induction, TGF-beta will induce the
transcriptional repression of transin, a transformation-associated
metalloprotease whose transcription is activated by the action of
several oncogenes and by EGF. In this application we propose to characterize the changes in
phosphoinositide metabolism in nontransformed and transformed
rat and mouse cell lines. We will investigate the ability of EGF
and TGF-beta to induce the production of diacylglycerols and
inositol phosphates and the mobilization of intracellular Ca2+.
Potential TGF-beta-modulated pathways will be investigated,
such as altered phospholipase C, DAG kinase and lipase activities.
In an effort to understand the differentiatial responsiveness to
TGF-beta of nontransformed and transformed cells, the
intracellular responses of some oncogen-transformed and
nontransformed cells to TGF-beta will be investigated. To
correlate the alteration in 2nd messenger production with
transcriptional repression induced by TGF-beta, alterations in
transin transcription will be measured using nuclear run-on
methods. Finally, in an effort to understand the regulation of
transin transcription by both EGF and TGF-beta, transient
expression assays will be performed using identified, and the
nucleotide sequences responsible for mediating EGF- and TGF-
beta-responsiveness of that gene will be identified. Thus, these
studies should be able to relate the alterations in 2nd messenger
production indeed by TGF-beta to the transcriptional
responsiveness of a gene whose transcription in repressed by TGF-
Effective start/end date4/5/886/30/95


  • National Institutes of Health: $133,286.00
  • National Institutes of Health: $20,759.00


  • Medicine(all)


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