The essential role of PP1beta in Drosophila is to regulate nonmuscle myosin.
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 PP1beta, a specific isoform of serine/threonine protein phosphatase 1 (PP1), regulates nonmuscle myosin and that this is the essential role of PP1beta. Loss of PP1beta 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 PP1beta, and activates PP1beta'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 PP1beta and MYPT genes suggests this role may be conserved.
Department of Zoology, University of Oxford, Oxford OX1 3PS, United Kingdom.
Natalia
N
Vereshchagina
Daimark
D
Bennett
Balázs
B
Szöor
Jasmin
J
Kirchner
Sascha
S
Gross
Emese
E
Vissi
Helen
H
White-Cooper
Luke
L
Alphey
D000595:Amino Acid Sequence; D000818:Animals; D003599:Cytoskeleton / Q000378:metabolism; D029721:Drosophila Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D018994:Myosin Light Chains / Q000235:genetics / Q000378:metabolism*; D043263:Myosin-Light-Chain Phosphatase / Q000145:classification / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D010749:Phosphoprotein Phosphatases / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D054645:Protein Phosphatase 1; D021122:Protein Subunits / Q000145:classification / Q000235:genetics / Q000378:metabolism
D029721:Drosophila Proteins; D007527:Isoenzymes; D018994:Myosin Light Chains; D021122:Protein Subunits; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D043263:Myosin-Light-Chain Phosphatase