The DH-PH region of the giant protein UNC-89 activates RHO-1 GTPase in C. elegans body wall muscle

• Type of Material: Article
• Authors: Hiroshi Qadota, Emory University; Anne Blangy, Centre de Recherche en Biologie cellulaire de Montpellier (CRBM); Ge Xiong, Emory University; Guy Benian, Emory University
• Language: English
• Date: 2008-11-21
• Publisher: Elsevier
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2008 Elsevier Ltd. All rights reserved.
• License: Creative Commons Attribution-NonCommerical-NoDerivs 3.0 Unported
• Final Published Version (URL): http://dx.doi.org/10.1016/j.jmb.2008.08.083
• Title of Journal or Parent Work: Journal of Molecular Biology
• ISSN: 0022-2836
• Volume: 383
• Issue: 4
• Start Page: 747
• End Page: 752
• Grant/Funding Information: The Caenorhabditis Genetics Center is supported by the National Center for Research Resources of the National Institutes of Health (NIH).; Support for this work was provided by NIAMS / NIH grant AR051466.
• Keywords: GEF; rho; obscurin; C. elegans; muscle; UNC-89
• Research Categories: Health Sciences, Pathology

Abstract

Mutation of the C. elegans gene unc-89 results in disorganization of muscle A-bands. unc-89 encodes a giant polypeptide (900 kDa) containing at its N-terminus, a DH followed by a PH domain, which is characteristic of guanine nucleotide exchange factor (GEF) proteins for Rho GTPases. To obtain evidence that the DH-PH region has activity toward specific Rho family small GTPases, we conducted an experiment using the yeast three hybrid system. The DH-PH region of UNC-89 has exchange activity for RHO-1 (C. elegans RhoA), but not for CED-10 (C. elegans Rac), MIG-2 (C. elegans RhoG), or CDC-42 (C. elegans Cdc42). The DH domain only also has similar activity for RHO-1. An in vitro binding assay demonstrates interaction between the DH-PH region of UNC-89 and each of the C. elegans Rho GTPases. Partial knock down of rho-1 in C. elegans adults showed a pattern of disorganization of myosin thick filaments, similar to the phenotype caused by unc-89 (su75), a mutant allele in which all of the isoforms containing the DH-PH region are missing. Taken together, we propose a model that the DH-PH region of UNC-89 activates RHO-1 GTPase for organization of myosin filaments in C. elegans muscle cells.