The TGFbeta superfamily regulates cell growth and differentiation. During Xenopus development, Nodal, Vg1 and activin-related signals induce endoderm and mesoderm, and BMP signals pattern these tissues and regulate ectodermal cell fate. The TGFbeta/activin and BMP pathways respectively transduce signals via Smads 2 and 3, or Smads1, 5 and 8. Little is known about TGFbeta signal downregulation. We have discovered two E3 ubiquitin ligases, Smurf1 and Smurf2, that inhibit BMP and TGFbeta/activin pathways, respectively (Zhu et al., 1999, Kavsak et al., 2000). Smurfs target Smads and receptors for ubiquitination and proteasomal degradation. While Smurf1 dorsalizes embryonic cell fates, the action of Smurf2 in embryos is unknown. We hypothesize that the Smurfs regulate tissue induction and pattern formation in embryogenesis by region-specific antagonism of TGFbeta signaling components. We will examine the role of Smurf1 and Smurf2 during embryogenesis and investigate the biochemical mechanisms necessary for Smurf regulation of development. Insight into Smurf functions will yield vital information about TGFbeta signaling and early development and will address pathologies such as birth defects, tissue degeneration and cancer, that result from defective regulation of TGFbeta signals or ubiquitin ligase functioning.
Aim 1. Do the Smurfs function in Xenopus embryonic development? We will establish the spatial distribution of Smurf proteins during embryogenesis, and determine the developmental effects of perturbing Smurf protein levels or activity.
Aim 2. How do Smurfs and TGFbeta signals regulate each other? To understand which signaling pathways Smurfs regulate in embryos, we will test the effects of Smurfs on components of BMP and activin signaling pathways, using biological (phenotype) and biochemical (interaction, ubiquitination) assays. We will determine whether Smurfs are regulated by TGFbeta, or other inductive signals, during development.
Aim 3. Identification and function of new Smurf interacting proteins. To obtain a comprehensive view of Smurf substrates and to find potential Smurf regulators, we will screen for and characterize Smurf-interacting proteins. We have already isolated 89 Smurf1-interacting clones, including Smad1, a known Smurf1 target.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD032429-06
Application #
6526299
Study Section
Cell Development and Function Integrated Review Group (CDF)
Program Officer
Klein, Steven
Project Start
2001-08-03
Project End
2006-07-31
Budget Start
2002-08-01
Budget End
2003-07-31
Support Year
6
Fiscal Year
2002
Total Cost
$338,625
Indirect Cost
Name
State University New York Stony Brook
Department
Biochemistry
Type
Schools of Arts and Sciences
DUNS #
804878247
City
Stony Brook
State
NY
Country
United States
Zip Code
11794
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Wang, Hong-Rui; Zhang, Yue; Ozdamar, Barish et al. (2003) Regulation of cell polarity and protrusion formation by targeting RhoA for degradation. Science 302:1775-9
Kavsak, P; Rasmussen, R K; Causing, C G et al. (2000) Smad7 binds to Smurf2 to form an E3 ubiquitin ligase that targets the TGF beta receptor for degradation. Mol Cell 6:1365-75
Zhu, H; Kavsak, P; Abdollah, S et al. (1999) A SMAD ubiquitin ligase targets the BMP pathway and affects embryonic pattern formation. Nature 400:687-93

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