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Proc Natl Acad Sci U S A. 1997 Nov 25;94(24):12938-43.

Smad8 mediates the signaling of the ALK-2 [corrected] receptor serine kinase.

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Clayton Foundation Laboratories for Peptide Biology, The Salk Institute, La Jolla, CA 92037, USA.

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  • Proc Natl Acad Sci U S A 1998 Feb 17;95(4):1968.


Smad proteins are critical intracellular mediators of signaling by growth and differentiation factors of the transforming growth factor beta superfamily. We have isolated a member of the Smad family, Smad8, from a rat brain cDNA library and biochemically and functionally characterized its ability to transduce signals from serine kinase receptors. In Xenopus embryo, Smad8 is able to transcriptionally activate a subset of mesoderm target genes similar to those induced by the receptor serine kinase, activin receptor-like kinase (ALK)-2. Smad8 can be specifically phosphorylated by a constitutively active ALK-2 but not the related receptor serine kinase, ALK-4. In response to signaling from ALK-2, Smad8 associates with a common regulatory molecule, Smad4, and this association leads to a synergistic effect on gene transcription. Furthermore, Smad8 is able to rescue the expression of mesoderm genes blocked by truncated ALK-2 in the embryo. These results indicate that Smad8 can function as a downstream signaling mediator of ALK-2.

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