Phactrs 1-4: A family of protein phosphatase 1 and actin regulatory proteins

Airway mucociliary clearance is a first-line defense of the lung against inhaled particles and debris. Among individuals with alcohol use disorders, there is an increase in lung diseases. We previously identified that prolonged alcohol exposure impairs mucociliary clearance, known as alcohol-induced ciliary dysfunction (AICD). Cilia-localized enzymes, known as the ciliary metabolon, are key to the pathogenesis of AICD. In AICD, cyclic nucleotide-dependent ciliary kinases, which modulate phosphorylation to regulate cilia beat, are desensitized. We hypothesized that alcohol activates cilia-associated protein phosphatase 1 (PP1) activity, driving phosphorylation changes of cilia motility regulatory proteins. To test this hypothesis we identified the effects of prolonged alcohol exposure on phosphatase activity, cilia beat, and kinase responsiveness and cilia-associated phosphorylation targets when stimulated by β-agonist or cAMP. Prolonged alcohol activated PP1 and blocked cAMP-dependent cilia beat and protein kinase A (PKA) responsiveness and phosphorylation of a 29-kDa substrate of PKA. Importantly, prolonged alcohol-induced phosphatase activation was inhibited by the PP1 specific inhibitor, inhibitor-2 (I-2), restoring cAMP-stimulated cilia beat and PKA responsiveness and phosphorylation of the 29-kDa substrate. The I-2 inhibitory effect persisted in tissue, cell, and isolated cilia-organelle models, highlighting the association of ciliary metabolon-localized enzymes to AICD. Prolonged alcohol exposure drives ciliary metabolon-localized PP1 activation. PP1 activation modifies phosphorylation of a 29-kDa protein related to PKA activity. These data reinforce our previous findings that alcohol is acting at the level of the ciliary metabolon to cause ciliary dysfunction and identifies PP1 as a therapeutic target to prevent or reverse AICD.

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Regulation of Alternative Splicing by Reversible Protein Phosphorylation

Journal of Biological Chemistry ◽

10.1074/jbc.r700034200 ◽

2007 ◽

Vol 283 (3) ◽

pp. 1223-1227 ◽

Cited By ~ 153

Author(s):

Stefan Stamm

Keyword(s):

Alternative Splicing ◽

Protein Phosphorylation ◽

Protein Phosphatase ◽

Single Gene ◽

Biological Properties ◽

Regulatory Proteins ◽

Protein Phosphatase 1 ◽

Splice Sites ◽

Reversible Protein Phosphorylation ◽

Selection Of

The vast majority of human protein-coding genes are subject to alternative splicing, which allows the generation of more than one protein isoform from a single gene. Cells can change alternative splicing patterns in response to a signal, which creates protein variants with different biological properties. The selection of alternative splice sites is governed by the dynamic formation of protein complexes on the processed pre-mRNA. A unique set of these splicing regulatory proteins assembles on different pre-mRNAs, generating a “splicing” or “messenger ribonucleoprotein code” that determines exon recognition. By influencing protein/protein and protein/RNA interactions, reversible protein phosphorylation modulates the assembly of regulatory proteins on pre-mRNA and therefore contributes to the splicing code. Studies of the serine/arginine-rich protein class of regulators identified different kinases and protein phosphatase 1 as the molecules that control reversible phosphorylation, which controls not only splice site selection, but also the localization of serine/arginine-rich proteins and mRNA export. The involvement of protein phosphatase 1 explains why second messengers like cAMP and ceramide that control the activity of this phosphatase influence alternative splicing. The emerging mechanistic links between splicing regulatory proteins and known signal transduction pathways now allow in detail the understanding how cellular signals modulate gene expression by influencing alternative splicing. This knowledge can be applied to human diseases that are caused by the selection of wrong splice sites.

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The structure of SDS22 provides insights into the mechanism of heterodimer formation with PP1

Acta Crystallographica Section F Structural Biology Communications ◽

10.1107/s2053230x18016503 ◽

2018 ◽

Vol 74 (12) ◽

pp. 817-824 ◽

Cited By ~ 1

Author(s):

Meng S. Choy ◽

Nicolas Bolik-Coulon ◽

Tara L. Archuleta ◽

Wolfgang Peti ◽

Rebecca Page

Keyword(s):

Protein Phosphatase ◽

Intrinsically Disordered Proteins ◽

Regulatory Proteins ◽

Protein Phosphatase 1 ◽

Disordered Proteins ◽

Biological Targets ◽

Intrinsically Disordered ◽

Intrinsically Disordered Regions ◽

Linear Motifs ◽

Lrr Protein

Protein phosphatase 1 (PP1) dephosphorylates hundreds of key biological targets by associating with nearly 200 regulatory proteins to form highly specific holoenzymes. The vast majority of regulators are intrinsically disordered proteins (IDPs) and bind PP1 via short linear motifs within their intrinsically disordered regions. One of the most ancient PP1 regulators is SDS22, a protein that is conserved from yeast to mammals. Sequence analysis of SDS22 revealed that it is a leucine-rich repeat (LRR) protein, suggesting that SDS22, unlike nearly every other known PP1 regulator, is not an IDP but instead is fully structured. Here, the 2.9 Å resolution crystal structure of human SDS22 in space group P212121 is reported. SDS22 adopts an LRR fold with the horseshoe-like curvature typical for this family of proteins. The structure results in surfaces with distinct chemical characteristics that are likely to be critical for PP1 binding.

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Regulation of protein phosphatase 1 by intrinsically disordered proteins

Biochemical Society Transactions ◽

10.1042/bst20120094 ◽

2012 ◽

Vol 40 (5) ◽

pp. 969-974 ◽

Cited By ~ 24

Author(s):

Meng S. Choy ◽

Rebecca Page ◽

Wolfgang Peti

Keyword(s):

Protein Phosphatase ◽

Intrinsically Disordered Proteins ◽

Critical Role ◽

Regulatory Proteins ◽

Protein Phosphatase 1 ◽

Disordered Proteins ◽

Tertiary Structures ◽

Binding Partner ◽

Intrinsically Disordered ◽

Biological Specificity

PP1 (protein phosphatase 1) is an essential serine/threonine phosphatase that plays a critical role in a broad range of biological processes, from muscle contraction to memory formation. PP1 achieves its biological specificity by forming holoenzymes with more than 200 known regulatory proteins. Interestingly, most of these regulatory proteins (≥70%) belong to the class of IDPs (intrinsically disordered proteins). Thus structural studies highlighting the interaction of these IDP regulatory proteins with PP1 are an attractive model system because it allows general parameters for a group of diverse IDPs that interact with the same binding partner to be identified, while also providing fundamental insights into PP1 biology. The present review provides a brief overview of our current understanding of IDP–PP1 interactions, including the importance of pre-formed secondary and tertiary structures for PP1 binding, as well as changes of IDP dynamics upon interacting with PP1.

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Folding of Intrinsically Disordered Protein Phosphatase 1 Regulatory Proteins

Current Physical Chemistry ◽

10.2174/1877946811202010107 ◽

2012 ◽

Vol 2 (1) ◽

pp. 107-114 ◽

Cited By ~ 7

Author(s):

Wolfgang Peti ◽

Angus C. Nairn ◽

Rebecca Page

Keyword(s):

Protein Phosphatase ◽

Intrinsically Disordered Protein ◽

Regulatory Proteins ◽

Protein Phosphatase 1 ◽

Intrinsically Disordered ◽

Disordered Protein

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Folding of Intrinsically Disordered Protein Phosphatase 1 Regulatory Proteins

Current Physical Chemistrye ◽

10.2174/1877947611202010107 ◽

2012 ◽

Vol 2 (1) ◽

pp. 107-114

Author(s):

Wolfgang Peti ◽

Angus C. Nairn ◽

Rebecca Page

Keyword(s):

Protein Phosphatase ◽

Intrinsically Disordered Protein ◽

Regulatory Proteins ◽

Protein Phosphatase 1 ◽

Intrinsically Disordered ◽

Disordered Protein

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SDS22 selectively recognizes and traps metal-deficient inactive PP1

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1908718116 ◽

2019 ◽

Vol 116 (41) ◽

pp. 20472-20481 ◽

Cited By ~ 2

Author(s):

Meng S. Choy ◽

Thomas M. Moon ◽

Rini Ravindran ◽

Johnny A. Bray ◽

Lucy C. Robinson ◽

...

Keyword(s):

Active Site ◽

Protein Phosphatase ◽

Regulatory Proteins ◽

Protein Phosphatase 1 ◽

Subunit Exchange ◽

Metal Loading ◽

Free Metal ◽

In Cells

The metalloenzyme protein phosphatase 1 (PP1), which is responsible for ≥50% of all dephosphorylation reactions, is regulated by scores of regulatory proteins, including the highly conserved SDS22 protein. SDS22 has numerous diverse functions, surprisingly acting as both a PP1 inhibitor and as an activator. Here, we integrate cellular, biophysical, and crystallographic studies to address this conundrum. We discovered that SDS22 selectively binds a unique conformation of PP1 that contains a single metal (M2) at its active site, i.e., SDS22 traps metal-deficient inactive PP1. Furthermore, we showed that SDS22 dissociation is accompanied by a second metal (M1) being loaded into PP1, as free metal cannot dissociate the complex and M1-deficient mutants remain constitutively trapped by SDS22. Together, our findings reveal that M1 metal loading and loss are essential for PP1 regulation in cells, which has broad implications for PP1 maturation, activity, and holoenzyme subunit exchange.

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