Danio rerio αE-catenin Is a Monomeric F-actin Binding Protein with Distinct Properties from Mus musculus αE-catenin

Phillip W Miller,Sabine Pokutta,Agnidipta Ghosh,Steven C Almo,William I Weis,W James Nelson,Adam V Kwiatkowski

doi:10.1074/jbc.m113.458406

Abstract

It is unknown whether homologs of the cadherin·catenin complex have conserved structures and functions across the Metazoa. Mammalian αE-catenin is an allosterically regulated actin-binding protein that binds the cadherin·β-catenin complex as a monomer and whose dimerization potentiates F-actin association. We tested whether these functional properties are conserved in another vertebrate, the zebrafish Danio rerio. Here we show, despite 90% sequence identity, that Danio rerio and Mus musculus αE-catenin have striking functional differences. We demonstrate that D. rerio αE-catenin is monomeric by size exclusion chromatography, native PAGE, and small angle x-ray scattering. D. rerio αE-catenin binds F-actin in cosedimentation assays as a monomer and as an α/β-catenin heterodimer complex. D. rerio αE-catenin also bundles F-actin, as shown by negative stained transmission electron microscopy, and does not inhibit Arp2/3 complex-mediated actin nucleation in bulk polymerization assays. Thus, core properties of α-catenin function, F-actin and β-catenin binding, are conserved between mouse and zebrafish. We speculate that unique regulatory properties have evolved to match specific developmental requirements.

Highlights

Mammalian ␣E-catenin is an allosterically regulated F-actin binding protein that inhibits the Arp2/3 complex
Domain Organization Is Conserved in D. rerio and M. musculus ␣E-catenin—We compared the amino acid sequences of D. rerio ␣E-catenin, M. musculus ␣E, ␣N, and ␣T-catenins, Drosophila melanogaster ␣-catenin, C. elegans HMP-1, D. discoideum ␣-catenin and M. musculus vinculin
D. rerio ␣E-catenin is similar to M. musculus ␣E-catenin, but not M. musculus vinculin, in domain organization (Fig. 1A) and amino acid sequence (Fig. 1B)

Summary

Background

Mammalian ␣E-catenin is an allosterically regulated F-actin binding protein that inhibits the Arp2/3 complex. Mammalian ␣E-catenin is an allosterically regulated actin-binding protein that binds the cadherin1⁄7␤-catenin complex as a monomer and whose dimerization potentiates F-actin association We tested whether these functional properties are conserved in another vertebrate, the zebrafish Danio rerio. 2 Present address: Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261. The amino acid sequence identities of C. elegans HMP-1 (␣-catenin) and D. discoideum ␣-catenin with M. musculus ␣E-catenin are low, 37 and 14%, respectively, and regulatory properties are not well conserved [12, 17,18,19]: C. elegans HMP-1 is an autoinhibited monomer that binds weakly to F-actin in solution [17, 18], and D. discoideum ␣-catenin is a monomer that constitutively binds and bundles F-actin but does not inhibit Arp2/3-mediated actin nucleation [19]. Despite the considerable sequence identity, there are remarkable differences in the functional properties of D. rerio ␣E-catenin

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION