Like the hormone estrogen, transforming growth factor beta (TGFb) is a
multifarious but Janus-faced molecule: Not only does it perform different
functions in different tissues, it also is capable of triggering opposite
effects. TGFb and other members of this so-called superfamily of growth factors
are able to spur the proliferation of cells, but also appear to suppress tumors;
they close wounds by generating and structuring new tissue, but also clog up and
stifle organs with unnecessary scar tissue For 20 years, researchers were perplexed about how one family of related
proteins can pull off such a bewildering array of feats in different tissues of
the body. How do the TGFbs convey a message encoding each distinct function
without the information getting scrambled? How are the receiving cells to know
just which of TGFb's many commands to carry out?
"We really know nothing about how the extracellular TGFb signals
actually translate into individual patterns of cell-type-specific gene
expression," says Malcolm Whitman, assistant professor of cell biology.
Now, Whitman and two coworkers have found the first answer for any
member of this family. The factor they studied, activin, binds to cells of the
very early frog embryo and Taken together, these studies introduce "a new class of signaling
pathway," says Whitman. Given TGFb's huge range of effects, it is "a
surprisingly simple one." Contrary to the long bucket brigades of proteins
required in previously known pathways, the TGFb pathway uses only one
protein
The authors of the Nature article, in addition to Whitman, are graduate student
Xin Chen and postdoctoral fellow Melissa Rubock, both in the Department of Cell
Biology at Harvard Medical School.
News Release
How Cells Listen to Many Voices-and Get Them Right / New Class of Signaling Pathway Gives Clues to Growth Factor's Powerful Effects
Peer-Reviewed Publication
BOSTON-Researchers at Harvard Medical School have uncovered the final steps in
the long-sought signaling cascade of a potent but mysterious family of growth
factors. Announced in the October 24 Nature, their discovery of a new protein
that provides the last link in a surprisingly short sequence of signaling events
helps pave the way to understanding an intriguing group of molecules. These
molecules play many still-shadowy roles in embryonic development, wound healing,
and cancer.