Functional analysis of ARHGAP6, a novel GTPase-activating protein for RhoA

• Published in: Human molecular genetics 2000-03, Vol.9 (4), p.477-488
• Main Authors: PRAKASH, S. K, PAYLOR, R, JENNA, S, LAMARCHE-VANES, N, ARMSTRONG, D. L, BISONG XU, MANCINI, M. A, ZOGHBI, H. Y
• Format: Article
• Language: English
• Subjects: Actins - metabolism; Actins - physiology; Alternative Splicing; Amino Acid Sequence; Animals; ARHGAP6 gene; ARHGAP6 protein; Behavior, Animal; Biological and medical sciences; cdc42 GTP-Binding Protein - physiology; Cytoplasm - physiology; Cytoskeleton - metabolism; Cytoskeleton - physiology; Exons; Female; GTPase-Activating Proteins - deficiency; GTPase-Activating Proteins - genetics; GTPase-Activating Proteins - isolation & purification; GTPase-Activating Proteins - physiology; Humans; Introns; Male; Malformations of the eye; Medical sciences; Mice; Mice, Inbred C57BL; Mice, Knockout; Microphthalmia with linear skin defects; Microphthalmos - genetics; Microphthalmos - pathology; Microphthalmos - physiopathology; Molecular Sequence Data; Muscle, Skeletal - abnormalities; Muscle, Skeletal - pathology; Ophthalmology; Peptide Fragments - physiology; rac1 GTP-Binding Protein - physiology; rhoA GTP-Binding Protein - deficiency; rhoA GTP-Binding Protein - genetics; rhoA GTP-Binding Protein - isolation & purification; rhoA GTP-Binding Protein - physiology; RhoA protein
• ISSN: 0964-6906; 1460-2083; 1460-2083
• DOI: 10.1093/hmg/9.4.477

Microphthalmia with linear skin defects (MLS) is an X-linked dominant, male-lethal syndrome characterized by microphthalmia, aplastic skin and agenesis of the corpus callosum, and is caused by the deletion of a 500 kb critical region in Xp22.3. Our laboratory isolated a novel rho GTPase-activating protein (rhoGAP) gene named ARHGAP6 from the MLS region. ARHGAP6 contains 14 exons encoding a 974 amino acid protein with three putative SH3-binding domains. Because exons 2-14 are deleted in all MLS patients, we hypothesized that ARHGAP6 may be responsible for some of the phenotypic features of MLS. We pursued two approaches to study the function of ARHGAP6 and its role in the pathogenesis of MLS: gene targeting of the rhoGAP domain in mouse embryonic stem cells and in vitro expression studies. Surprisingly, loss of the rhoGAP function of Arhgap6 does not cause any detectable phenotypic or behavioral abnormalities in the mutant mice. Transfected mammalian cells expressing ARHGAP6 lose their actin stress fibers, retract from the growth surface and extend thin, branching processes resembling filopodia. The ARHGAP6 protein co-localizes with actin filaments through an N-terminal domain and recruits F-actin into the growing processes. Mutation of a conserved arginine residue in the rhoGAP domain prevents the loss of stress fibers but has little effect on process outgrowth. These results suggest that ARHGAP6 has two independent functions: one as a GAP with specificity for RhoA and the other as a cytoskeletal protein that promotes actin remodeling.