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A more recent version of this article appeared on October 1, 2004
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Submitted on February 19, 2004
Revised on July 2, 2004
Accepted on July 12, 2004
in Drosophila Is To Regulate Non-Muscle Myosin
r,
Department of Zoology, University of Oxford, Oxford OX1 3PS, United Kingdom
Monitoring Editor: Lawrence Goldstein
Reversible phosphorylation of myosin regulatory light chain (MRLC) is a key regulatory mechanism controlling myosin activity, and thus regulating the actin/myosin cytoskeleton. We show that Drosophila PP1
, a specific isoform of serine/threonine protein phosphatase 1 (PP1), regulates nonmuscle myosin and that this is the essential role of PP1
. Loss of PP1
leads to increased levels of phosphorylated nonmuscle MRLC (Sqh) and actin disorganisation; these phenotypes can be suppressed by reducing the amount of active myosin. Drosophila has two nonmuscle myosin targeting subunits, one of which (MYPT-75D) resembles MYPT3, binds specifically to PP1
and activates PP1
s Sqh phosphatase activity. Expression of a mutant form of MYPT-75D that is unable to bind PP1 results in elevation of Sqh phosphorylation in vivo and leads to phenotypes that can also be suppressed by reducing the amount of active myosin. The similarity between fly and human PP1
and MYPT genes suggests this role may be conserved.
Corresponding author.
E-mail: Luke.Alphey{at}zoo.ox.ac.uk