title: Tropomodulin protects α-catenin-dependent junctional-actin networks under stress during epithelial morphogenesis.
abstract: α-catenin is central to recruitment of actin networks to the cadherin-catenin complex, but how such networks are subsequently stabilized against stress applied during morphogenesis is poorly understood. To identify proteins that functionally interact with α-catenin in this process, we performed enhancer screening using a weak allele of the C. elegans α-catenin, hmp-1, thereby identifying UNC-94/tropomodulin. Tropomodulins (Tmods) cap the minus ends of F-actin in sarcomeres. They also regulate lamellipodia, can promote actin nucleation, and are required for normal cardiovascular development and neuronal growth-cone morphology. Tmods regulate the morphology of cultured epithelial cells, but their role in epithelia in vivo remains unexplored. We find that UNC-94 is enriched within a HMP-1-dependent junctional-actin network at epidermal adherens junctions subject to stress during morphogenesis. Loss of UNC-94 leads to discontinuity of this network, and high-speed filming of hmp-1(fe4);unc-94(RNAi) embryos reveals large junctional displacements that depend on the Rho pathway. In vitro, UNC-94 acts in combination with HMP-1, leading to longer actin bundles than with HMP-1 alone. Our data suggest that Tmods protect actin filaments recruited by α-catenin from minus-end subunit loss, enabling them to withstand the stresses of morphogenesis.
authors: Department of Biology, State University of New York at Geneseo, 353 Integrated Science Center, 1 College Circle, Geneseo, NY 14454, USA.
authors: Elisabeth A
authors: EA
authors: Cox-Paulson
authors: Elise
authors: E
authors: Walck-Shannon
authors: Allison M
authors: AM
authors: Lynch
authors: Sawako
authors: S
authors: Yamashiro
authors: Ronen
authors: R
authors: Zaidel-Bar
authors: Celeste C
authors: CC
authors: Eno
authors: Shoichiro
authors: S
authors: Ono
authors: Jeff
authors: J
authors: Hardin
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D017173:Caenorhabditis elegans; D004817:Epidermis / Q000196:embryology; D009024:Morphogenesis; D013314:Stress, Mechanical; D051348:Tropomodulin / Q000378:metabolism*; D051178:alpha Catenin / Q000378:metabolism*
chemical_list: D000199:Actins; D051348:Tropomodulin; D051178:alpha Catenin