title: Apical Sarcomere-like Actomyosin Contracts Nonmuscle Drosophila Epithelial Cells.
abstract: Actomyosin networks generate contractile force that changes cell and tissue shape. In muscle cells, actin filaments and myosin II appear in a polarized structure called a sarcomere, in which myosin II is localized in the center. Nonmuscle cortical actomyosin networks are thought to contract when nonmuscle myosin II (myosin) is activated throughout a mixed-polarity actin network. Here, we identified a mutant version of the myosin-activating kinase, ROCK, that localizes diffusely, rather than centrally, in epithelial cell apices. Surprisingly, this mutant inhibits constriction, suggesting that centrally localized apical ROCK/myosin activity promotes contraction. We determined actin cytoskeletal polarity by developing a barbed end incorporation assay for Drosophila embryos, which revealed barbed end enrichment at junctions. Our results demonstrate that epithelial cells contract with a spatially organized apical actomyosin cortex, involving a polarized actin cytoskeleton and centrally positioned myosin, with cell-scale order that resembles a muscle sarcomere.
authors: Department of Biology, Massachusetts Institute of Technology, 31 Ames Street, Cambridge, MA 02142, USA.
authors: Jonathan S
authors: JS
authors: Coravos
authors: Department of Biology, Massachusetts Institute of Technology, 31 Ames Street, Cambridge, MA 02142, USA. Electronic address: acmartin@mit.edu.
authors: Adam C
authors: AC
authors: Martin
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism; D000205:Actomyosin / Q000378:metabolism*; D000818:Animals; D016764:Cell Polarity; D048430:Cell Shape; D029721:Drosophila Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000166:cytology / Q000196:embryology; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism; D008954:Models, Biological; D009024:Morphogenesis; D009119:Muscle Contraction; D009132:Muscles / Q000166:cytology*; D024462:Myosin Type II / Q000378:metabolism; D012518:Sarcomeres / Q000378:metabolism; D054460:rho-Associated Kinases / Q000378:metabolism
chemical_list: D000199:Actins; D029721:Drosophila Proteins; D000205:Actomyosin; D054460:rho-Associated Kinases; D024462:Myosin Type II
keywords: ROCK; actin cortex; cell polarity; contraction; epithelia; morphogenesis; myosin; sarcomere