Distinct tissue distributions and subcellular localizations of differently phosphorylated forms of the myosin regulatory light chain in Drosophila

Gene Expr Patterns. Jan-Feb 2011;11(1-2):93-104. doi: 10.1016/j.gep.2010.09.008. Epub 2010 Oct 30.

Abstract

Nonmuscle myosin II (myosin hereafter) has well-established roles in generating contractile force on actin filaments during morphogenetic processes in all metazoans. Myosin activation is regulated by phosphorylation of the myosin regulatory light chain (MRLC, encoded by spaghettisquash or sqh in Drosophila) first on Ser21 and subsequently on Thr20. These phosphorylation events are positively controlled by a variety of kinases including myosin light chain kinase, Rho kinase, citron kinase, and AMP kinase and are negatively regulated by myosin phosphatase. The activation of myosin is thus highly regulated and likely developmentally controlled. In order to monitor the activity of myosin during development, we have generated antibodies against the monophosphorylated (Sqh1P) and diphosphorylated (Sqh2P) forms of Sqh. We first show that the antibodies are highly specific. We then used these antibodies to monitor myosin activation in wild type Drosophila tissues. Interestingly, Sqh1P and Sqh2P show distinct patterns of expression in embryos. Sqh1P is expressed nearly ubiquitously and outlines cells consistent with a junctional localization, whereas Sqh2P is strongly expressed on the apical surfaces and in filopodia of tissues undergoing extensive cell shape change or cell movements including the invaginating fore- and hindgut, the invaginating tracheal system, the dorsal pouch and the dorsal most row of epidermal (DME) cells during dorsal closure. In imaginal discs, Sqh1P predominantly localizes in the adherens junction, whereas Sqh2P locates to the apical domain. These antibodies thus have the potential to be very useful in monitoring myosin activation for functional studies of morphogenesis in Drosophila.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Drosophila Proteins / analysis*
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism*
  • Drosophila melanogaster / embryology*
  • Drosophila melanogaster / genetics
  • Drosophila melanogaster / metabolism*
  • Myosin Light Chains / analysis
  • Myosin Light Chains / genetics
  • Myosin Light Chains / metabolism
  • Myosin Type II / analysis*
  • Myosin Type II / genetics
  • Myosin Type II / metabolism*
  • Organ Specificity
  • Phosphorylation

Substances

  • Drosophila Proteins
  • Myosin Light Chains
  • Sqh protein, Drosophila
  • Myosin Type II