The cadherin-catenin complex (CCC) is crucial for successful completion of morphogenesis during embryonic development, and for suppression of metastatic phenotypes in differentiated epithelia. Beta-catenin is a core component of the CCC;analyzing and manipulating the adhesive functions of beta-catenin thus has widespread implications for human health. To date, distinguishing between adhesion and Tcf/Lef-dependent transcriptional coactivator functions of beta-catenin, and correlating detailed protein structural information with in vivo function has been challenging in vertebrates. C. elegans presents a unique opportunity to analyze the adhesion- specific roles of a beta-catenin, because it possesses multiple, specialized beta -catenins. We will leverage this unique specialization, combined with a powerful foundation of detailed structural information derived from a collaborative X-ray crystallography project, to establish a new, multi- disciplinary approach to the study of beta-catenins in the following aims:
Aim 1. Test the role of a key phosphorylated residue in the C terminus of cadherin for the first time in vivo. We will test the in vivo importace of phosphorylation of a conserved serine that upregulates the affinity of cadherin for beta-catenin several hundred fold in vitro using biochemical and high-resolution microscopy in living embryos.
Aim 2. Test the role of key phosphotyrosines in the adhesive functions of beta-catenin for the first time in vivo. We will test the in vivo importance of two highly conserved tyrosines, one that regulates cadherin/beta-catenin binding, and another that regulates beta-catenin/beta-catenin binding. We will also assess the phosphorylation state of endogenous HMP-2 using affinity purification and mass spectrometry and identify a panel of new hmp-2 alleles, which will provide information about amino acids important specifically for the adhesive functions of beta-catenin.
Aim 3. Test the role of a conserved helical domain in beta-catenin for its activity as a transcriptional coactivator. HMP-2 lacks a helical domain ("Helix C") just C-terminal to the 12th Arm repeat that is conserved in all beta-catenins known to have canonical transcriptional co- activator functions. BAR-1 binds POP-1/Tcf with high affinity, and retains Helix C. We will test the role of Helix C using domain-swap experiments between HMP-2 and BAR-1, and assessing Tcf binding in vitro and coactivator functions in vivo.

Public Health Relevance

Understanding how cells attach to one another is important for understanding many common birth defects, and how cancer cells lose their connections to one another and invade the body. This proposal examines a key protein, beta-catenin that regulates cell adhesiveness, and how this protein works together with other proteins to ensure that cells make proper connections in the body. By studying how this protein works in living embryos, we will gain important information that can be used to understand and treat human disease.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Exploratory/Developmental Grants (R21)
Project #
1R21HD072769-01
Application #
8320628
Study Section
Intercellular Interactions (ICI)
Program Officer
Mukhopadhyay, Mahua
Project Start
2012-03-01
Project End
2014-02-28
Budget Start
2012-03-01
Budget End
2013-02-28
Support Year
1
Fiscal Year
2012
Total Cost
$184,085
Indirect Cost
$59,085
Name
University of Wisconsin Madison
Department
Zoology
Type
Schools of Arts and Sciences
DUNS #
161202122
City
Madison
State
WI
Country
United States
Zip Code
53715
Hardin, Jeff; Lynch, Allison; Loveless, Timothy et al. (2013) Cadherins and their partners in the nematode worm Caenorhabditis elegans. Prog Mol Biol Transl Sci 116:239-62