In vitro and in vivo reconstitution of the cadherin–catenin–actin complex from Caenorhabditis elegans — PNAS

In vitro and in vivo reconstitution of the cadherin–catenin–actin complex from Caenorhabditis elegans
Adam V. Kwiatkowskia,1, Stephanie L. Maidenb,1, Sabine Pokuttac, Hee-Jung Choic, Jacqueline M. Benjamina, Allison M. Lynchd, W. James Nelsona,e,2, William I. Weisc,e,2, and Jeff Hardinb,2
+ Author Affiliations

aDepartment of Biology, Stanford University, 318 Campus Drive, Stanford, CA 94305;
bMolecular and Cellular Pharmacology Program and Department of Zoology, University of Wisconsin, 1117 West Johnson Street, Madison, WI 53706;
cDepartment of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305;
dProgram in Genetics, University of Wisconsin, 1117 West Johnson Street, Madison, WI 53706; and
eDepartment of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305
Edited by Vann Bennett, Duke University Medical Center, Durham, NC, and approved July 6, 2010 (received for review May 26, 2010)

↵1A.V.K. and S.L.M. contributed equally to this work.

Abstract
The ternary complex of cadherin, β-catenin, and α-catenin regulates actin-dependent cell–cell adhesion. α-Catenin can bind β-catenin and F-actin, but in mammals α-catenin either binds β-catenin as a monomer or F-actin as a homodimer. It is not known if this conformational regulation of α-catenin is evolutionarily conserved. The Caenorhabditis elegans α-catenin homolog HMP-1 is essential for actin-dependent epidermal enclosure and embryo elongation. Here we show that HMP-1 is a monomer with a functional C-terminal F-actin binding domain. However, neither full-length HMP-1 nor a ternary complex of HMP-1–HMP-2(β-catenin)–HMR-1(cadherin) bind F-actin in vitro, suggesting that HMP-1 is auto-inhibited. Truncation of either the F-actin or HMP-2 binding domain of HMP-1 disrupts C. elegans development, indicating that HMP-1 must be able to bind F-actin and HMP-2 to function in vivo. Our study defines evolutionarily conserved properties of α-catenin and suggests that multiple mechanisms regulate α-catenin binding to F-actin.

cell–cell adhesionHMP-1HMP-2HMR-1

Footnotes
2To whom correspondence may be addressed. E-mail: jdhardin@wisc.edu, bill.weis@stanford.edu, or wjnelson@stanford.edu. Author contributions: A.V.K., S.L.M., W.J.N., W.I.W., and J.H. designed research; A.V.K., S.L.M., S.P., and H.-J.C. performed research; J.M.B. and A.M.L. contributed new reagents/analytic tools; A.V.K., S.L.M., S.P., H.-J.C., W.J.N., W.I.W., and J.H. analyzed data; and A.V.K., S.L.M., W.J.N., W.I.W., and J.H. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at
www.pnas.org/lookup/suppl/doi:10.1073/pnas.1007349107/-/DCSupplemental.

In vitro and in vivo reconstitution of the cadherin–catenin–actin complex from Caenorhabditis elegans — PNAS