Caenorhabditis elegans unc-82 Encodes a Serine/Threonine Kinase Important for Myosin Filament Organization in Muscle During Growth by ProQuest

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Mutations in the unc-82 locus of Caenorhabditis elegans were previously identified by screening for disrupted muscle cytoskeleton in otherwise apparently normal mutagenized animals. Here we demonstrate that the locus encodes a serine/threonine kinase orthologous to human ARK5/SNARK (NUAK1/NUAK2) and related to the PAR-1 and SNF1/AMP-Activated kinase (AMPK) families. The predicted 1600-amino-acid polypeptide contains an N-terminal catalytic domain and noncomplex repetitive sequence in the remainder of the molecule. Phenotypic analyses indicate that unc-82 is required for maintaining the organization of myosin filaments and internal components of the M-line during cell-shape changes. Mutants exhibit normal patterning of cytoskeletal elements during early embryogenesis. Defects in localization of thick filament and M-line components arise during embryonic elongation and become progressively more severe as development proceeds. The phenotype is independent of contractile activity, consistent with unc-82 mutations preventing proper cytoskeletal reorganization during growth, rather than undermining structural integrity of the M-line. This is the first report establishing a role for the UNC-82/ARK5/SNARK kinases in normal development. We propose that activation of UNC-82 kinase during cell elongation regulates thick filament attachment or growth, perhaps through phosphorylation of myosin and paramyosin. We speculate that regulation of myosin is an ancestral characteristic of kinases in this region of the kinome. [PUBLICATION ABSTRACT]

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									Copyright Ó 2010 by the Genetics Society of America
DOI: 10.1534/genetics.109.110189



Caenorhabditis elegans unc-82 Encodes a Serine/Threonine Kinase Important
       for Myosin Filament Organization in Muscle During Growth

           Pamela E. Hoppe,*,†,1 Johnnie Chau,*,2,3 Kelly A. Flanagan,*,2,4 April R. Reedy†,2,5
                                    and Lawrence A. Schriefer*
     †
      Department of Biological Sciences, Western Michigan University, Kalamazoo, Michigan 49008-5410 and *Department of Genetics,
                                    Washington University School of Medicine, St. Louis, Missouri 63110
                                                      Manuscript received September 23, 2009
                                                        Accepted for publication November 1, 2009


                                                             ABSTRACT
                Mutations in the unc-82 locus of Caenorhabditis elegans were previously identified by screening for
              disrupted muscle cytoskeleton in otherwise apparently normal mutagenized animals. Here we
              demonstrate that the locus encodes a serine/threonine kinase orthologous to human ARK5/SNARK
              (NUAK1/NUAK2) and related to the PAR-1 and SNF1/AMP-Activated kinase (AMPK) families. The
              predicted 1600-amino-acid polypeptide contains an N-terminal catalytic domain and noncomplex
              repetitive sequence in the remainder of the molecule. Phenotypic analyses indicate that unc-82 is required
              for maintaining the organization of myosin filaments and internal components of the M-line during cell-
              shape changes. Mutants exhibit normal patterning of cytoskeletal elements during early embryogenesis.
              Defects in localization of thick filament and M-line components arise during embryonic elongation and
              become progressively more severe as development proceeds. The phenotype is independent of contractile
              activity, consistent with unc-82 mutations preventing proper cytoskeletal reorganization during growth,
              rather than undermining structural integrity of the M-line. This is the first report establishing a role for
              the UNC-82/ARK5/SNARK kinases in normal development. We propose that activation of UNC-82 kinase
              during cell elongation regulates thick filament attachment or growth, perhaps through phosphorylation
              of myosin and paramyosin. We speculate that regulation of myosin is an ancestral characteristic of kinases
              in this region of the kinome.




T   HE contractile apparatus of striated muscle is a
      highly ordered cytoskeletal structure (Figure 1)
composed of actin and myosin filaments, the filament
                                                                            force of muscle-cell contraction to the epidermis and
                                                                            its secreted cuticle and allows the worm to locomote
                                                                            through its environment. The patterning of the
anchoring structures, and a host of regulatory proteins.                    contractile apparatus occurs through integrin-medi-
During Caenorhabditis elegans embryogenesis, the body-                      ated signaling at the plasma membrane where muscle
wall muscle cells polarize and assemble their cytoske-                      cells contact the epidermis. The assembly of more
letons in response to contact with the epidermal cells,                     interior (membrane-distal) components of the con-
to which they attach through focal-adhesion-like                            tractile apparatus follows and requires the membrane-
structures. The epidermal cells respond in a similar                        proximal events (Hresko et al. 1994). Failure to
fashion and assemble attachment structures and                              assemble functional epidermal–muscle-cell contacts
fibrous organelles at the sites of muscle-cell contact                       or failure to make contractile muscle cells prevents
(reviewed in Moerman and Williams 2006). The                                elongation of the embryo from an egg shape into a long
coordination of the cytoskeletons of the two tissue types                   tube. Many genes required for these early patterning
provides the physical attachment that transmits the                         events, as well as those essential for muscle contraction,
                                                                            have bee
								
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