Abstract
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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Animals
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Cytoskeleton / metabolism
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Drosophila Proteins / classification
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Drosophila Proteins / genetics
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Drosophila Proteins / metabolism
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Drosophila melanogaster / anatomy & histology
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Drosophila melanogaster / genetics
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Drosophila melanogaster / metabolism*
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Humans
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Isoenzymes / classification
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Isoenzymes / genetics
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Isoenzymes / metabolism*
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Male
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Molecular Sequence Data
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Mutation
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Myosin Light Chains / genetics
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Myosin Light Chains / metabolism*
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Myosin-Light-Chain Phosphatase / classification
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Myosin-Light-Chain Phosphatase / genetics
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Myosin-Light-Chain Phosphatase / metabolism
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Phenotype
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Phosphoprotein Phosphatases / classification
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Phosphoprotein Phosphatases / genetics
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Phosphoprotein Phosphatases / metabolism*
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Phosphorylation
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Protein Binding
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Protein Phosphatase 1
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Protein Subunits / classification
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Protein Subunits / genetics
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Protein Subunits / metabolism
Substances
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Drosophila Proteins
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Isoenzymes
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Myosin Light Chains
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Protein Subunits
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Phosphoprotein Phosphatases
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Protein Phosphatase 1
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Myosin-Light-Chain Phosphatase