Cargando…

Myosin Light Chain–activating Phosphorylation Sites Are Required for Oogenesis in Drosophila

The Drosophila spaghetti squash (sqh) gene encodes the regulatory myosin light chain (RMLC) of nonmuscle myosin II. Biochemical analysis of vertebrate nonmuscle and smooth muscle myosin II has established that phosphorylation of certain amino acids of the RMLC greatly increases the actin-dependent m...

Descripción completa

Detalles Bibliográficos
Autores principales: Jordan, Pascale, Karess, Roger
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1997
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2132636/
https://www.ncbi.nlm.nih.gov/pubmed/9412474
_version_ 1782142491010531328
author Jordan, Pascale
Karess, Roger
author_facet Jordan, Pascale
Karess, Roger
author_sort Jordan, Pascale
collection PubMed
description The Drosophila spaghetti squash (sqh) gene encodes the regulatory myosin light chain (RMLC) of nonmuscle myosin II. Biochemical analysis of vertebrate nonmuscle and smooth muscle myosin II has established that phosphorylation of certain amino acids of the RMLC greatly increases the actin-dependent myosin ATPase and motor activity of myosin in vitro. We have assessed the in vivo importance of these sites, which in Drosophila correspond to serine-21 and threonine-20, by creating a series of transgenes in which these specific amino acids were altered. The phenotypes of the transgenes were examined in an otherwise null mutant background during oocyte development in Drosophila females. Germ line cystoblasts entirely lacking a functional sqh gene show severe defects in proliferation and cytokinesis. The ring canals, cytoplasmic bridges linking the oocyte to the nurse cells in the egg chamber, are abnormal, suggesting a role of myosin II in their establishment or maintenance. In addition, numerous aggregates of myosin heavy chain accumulate in the sqh null cells. Mutant sqh transgene sqh-A20, A21 in which both serine-21 and threonine-20 have been replaced by alanines behaves in most respects identically to the null allele in this system, with the exception that no heavy chain aggregates are found. In contrast, expression of sqh-A21, in which only the primary phosphorylation target serine-21 site is altered, partially restores functionality to germ line myosin II, allowing cystoblast division and oocyte development, albeit with some cytokinesis failure, defects in the rapid cytoplasmic transport from nurse cells to cytoplasm characteristic of late stage oogenesis, and some damaged ring canals. Substituting a glutamate for the serine-21 (mutant sqh-E21) allows oogenesis to be completed with minimal defects, producing eggs that can develop normally to produce fertile adults. Flies expressing sqh-A20, in which only the secondary phosphorylation site is absent, appear to be entirely wild type. Taken together, this genetic evidence argues that phosphorylation at serine-21 is critical to RMLC function in activating myosin II in vivo, but that the function can be partially provided by phosphorylation at threonine-20.
format Text
id pubmed-2132636
institution National Center for Biotechnology Information
language English
publishDate 1997
publisher The Rockefeller University Press
record_format MEDLINE/PubMed
spelling pubmed-21326362008-05-01 Myosin Light Chain–activating Phosphorylation Sites Are Required for Oogenesis in Drosophila Jordan, Pascale Karess, Roger J Cell Biol Article The Drosophila spaghetti squash (sqh) gene encodes the regulatory myosin light chain (RMLC) of nonmuscle myosin II. Biochemical analysis of vertebrate nonmuscle and smooth muscle myosin II has established that phosphorylation of certain amino acids of the RMLC greatly increases the actin-dependent myosin ATPase and motor activity of myosin in vitro. We have assessed the in vivo importance of these sites, which in Drosophila correspond to serine-21 and threonine-20, by creating a series of transgenes in which these specific amino acids were altered. The phenotypes of the transgenes were examined in an otherwise null mutant background during oocyte development in Drosophila females. Germ line cystoblasts entirely lacking a functional sqh gene show severe defects in proliferation and cytokinesis. The ring canals, cytoplasmic bridges linking the oocyte to the nurse cells in the egg chamber, are abnormal, suggesting a role of myosin II in their establishment or maintenance. In addition, numerous aggregates of myosin heavy chain accumulate in the sqh null cells. Mutant sqh transgene sqh-A20, A21 in which both serine-21 and threonine-20 have been replaced by alanines behaves in most respects identically to the null allele in this system, with the exception that no heavy chain aggregates are found. In contrast, expression of sqh-A21, in which only the primary phosphorylation target serine-21 site is altered, partially restores functionality to germ line myosin II, allowing cystoblast division and oocyte development, albeit with some cytokinesis failure, defects in the rapid cytoplasmic transport from nurse cells to cytoplasm characteristic of late stage oogenesis, and some damaged ring canals. Substituting a glutamate for the serine-21 (mutant sqh-E21) allows oogenesis to be completed with minimal defects, producing eggs that can develop normally to produce fertile adults. Flies expressing sqh-A20, in which only the secondary phosphorylation site is absent, appear to be entirely wild type. Taken together, this genetic evidence argues that phosphorylation at serine-21 is critical to RMLC function in activating myosin II in vivo, but that the function can be partially provided by phosphorylation at threonine-20. The Rockefeller University Press 1997-12-29 /pmc/articles/PMC2132636/ /pubmed/9412474 Text en This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
spellingShingle Article
Jordan, Pascale
Karess, Roger
Myosin Light Chain–activating Phosphorylation Sites Are Required for Oogenesis in Drosophila
title Myosin Light Chain–activating Phosphorylation Sites Are Required for Oogenesis in Drosophila
title_full Myosin Light Chain–activating Phosphorylation Sites Are Required for Oogenesis in Drosophila
title_fullStr Myosin Light Chain–activating Phosphorylation Sites Are Required for Oogenesis in Drosophila
title_full_unstemmed Myosin Light Chain–activating Phosphorylation Sites Are Required for Oogenesis in Drosophila
title_short Myosin Light Chain–activating Phosphorylation Sites Are Required for Oogenesis in Drosophila
title_sort myosin light chain–activating phosphorylation sites are required for oogenesis in drosophila
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2132636/
https://www.ncbi.nlm.nih.gov/pubmed/9412474
work_keys_str_mv AT jordanpascale myosinlightchainactivatingphosphorylationsitesarerequiredforoogenesisindrosophila
AT karessroger myosinlightchainactivatingphosphorylationsitesarerequiredforoogenesisindrosophila