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Gene Mar 2023Stroke had emerged as one of the leading causes of death and long-term disability across the globe. Emerging evidence suggests a significant increase in the incidence of... (Review)
Review
Stroke had emerged as one of the leading causes of death and long-term disability across the globe. Emerging evidence suggests a significant increase in the incidence of stroke with age, which is further expected to increase dramatically owing to an ever-expanding elderly population. The current situation imposes a significant burden on the healthcare system and requires a deeper understanding of the underlying mechanisms and development of novel interventions. It is well established that mitochondrial dysfunction plays a pivotal role in the onset of stroke. Dynamin-related protein 1 (Drp1), is a key regulator of mitochondria fission, and plays a crucial role during the pathogenesis of stroke. Drp1 protein levels significantly increase after stroke potentially in a p38 mitogen-activated protein kinases (MAPK) dependent manner. Protein phosphatase 2A (PP2A) facilitate mitochondrial fission and cell death by dephosphorylating the mitochondrial fission enzyme Drp1 at the inhibitory phosphorylation site serine 637. Outer mitochondrial membrane A-Kinase Anchoring Proteins 1 (AKAP 1) and protein kinase A complex (PKA) complex inhibits Drp1-dependent mitochondrial fission by phosphorylating serine 637. Drp1 activation promotes the release of cytochrome C from mitochondria and therefore leads to apoptosis. In addition, Drp1 activation inhibits mitochondrial glutathione dependent free radical scavenging, which further enhances the ROS level and exacerbate mitochondrial dysfunction. Drp1 translocate p53 to mitochondrial membrane and leads to mitochondria-related necrosis. The current review article discusses the possible mechanistic pathways by which Drp1 can influence the pathogenesis of stroke. Besides, it will describe various inhibitors for Drp1 and their potential role as therapeutics for stroke in the future.
Topics: Aged; Humans; Phosphorylation; Dynamins; Mitochondria; Stroke; Apoptosis; Serine; Mitochondrial Proteins
PubMed: 36543307
DOI: 10.1016/j.gene.2022.147130 -
Cell Death & Disease Jun 2023The Raptor signaling pathway is a critical point of intervention in the invasion and progression of cancer. The non-receptor tyrosine kinase Src-mediated phosphorylation...
The Raptor signaling pathway is a critical point of intervention in the invasion and progression of cancer. The non-receptor tyrosine kinase Src-mediated phosphorylation of OTUB1-Y26 plays a critical role in Raptor stabilization, whereas cathepsin K inhibitor (odanacatib; ODN) and knockdown (siRNA) induce Raptor destabilization. However, the mechanisms involved in cathepsin K inhibition-induced OTUB1-Y26 phosphorylation in Raptor stabilization have not been yet elucidated. This study showed that cathepsin K inhibition activates SHP2, a tyrosine phosphatase, that dephosphorylates OTUB1 and destabilizes Raptor, whereas SHP2 deletion and pharmacological inhibition increase OTUB1-Y26 phosphorylation and Raptor expression. SHP2 deletion also led to the inhibition of ODN-induced mitochondrial ROS, fusion, and dysfunction. Furthermore, cathepsin K inhibition phosphorylated spleen tyrosine kinase (Syk) at Y525 and Y526, resulting in the SHP2-mediated dephosphorylation of OTUB1-Y26. Collectively, our findings identified Syk not only as an upstream tyrosine kinase required for SHP2 activation but also showed a critical mechanism that regulates ODN-induced Raptor downregulation and mitochondrial dysfunction. In conclusion, Syk/SHP2/Src/OTUB1 axis-mediated signaling can act as a therapeutic target in cancer management.
Topics: Cathepsin K; Protein Tyrosine Phosphatase, Non-Receptor Type 11; Signal Transduction; Protein-Tyrosine Kinases; Phosphorylation; Mitochondria
PubMed: 37330581
DOI: 10.1038/s41419-023-05884-z -
Plant, Cell & Environment Oct 2019Protein phosphorylation is a key signalling mechanism and has myriad effects on protein function. Phosphorylation by protein kinases can be reversed by protein... (Review)
Review
Protein phosphorylation is a key signalling mechanism and has myriad effects on protein function. Phosphorylation by protein kinases can be reversed by protein phosphatases, thus allowing dynamic control of protein phosphorylation. Although this may suggest a straightforward kinase-phosphatase relationship, plant genomes contain five times more kinases than phosphatases. Here, we examine phospho-signalling from a protein phosphatase centred perspective and ask how relatively few phosphatases regulate many phosphorylation sites. The most abundant class of plant phosphatases, the protein phosphatase 2Cs (PP2Cs), is surrounded by a web of regulation including inhibitor and activator proteins as well as posttranslational modifications that regulate phosphatase activity, control phosphatase stability, or determine the subcellular locations where the phosphatase is present and active. These mechanisms are best established for the Clade A PP2Cs, which are key components of stress and abscisic acid signalling. We also describe other PP2C clades and illustrate how these phosphatases are highly regulated and involved in a wide range of physiological functions. Together, these examples of multiple layers of phosphatase regulation help explain the unbalanced kinase-phosphatase ratio. Continued use of phosphoproteomics to examine phosphatase targets and phosphatase-kinase relationships will be important for deeper understanding of phosphoproteome regulation.
Topics: Enzyme Stability; Phosphorylation; Plant Proteins; Protein Kinases; Protein Phosphatase 2C; Protein Processing, Post-Translational; Signal Transduction
PubMed: 31314921
DOI: 10.1111/pce.13616 -
Biomolecules Nov 2022Protein phosphorylation and dephosphorylation are widely considered to be the key regulatory factors of cell function, and are often referred to as "molecular switches"... (Review)
Review
Protein phosphorylation and dephosphorylation are widely considered to be the key regulatory factors of cell function, and are often referred to as "molecular switches" in the regulation of cell metabolic processes. A large number of studies have shown that the phosphorylation/dephosphorylation of related signal molecules plays a key role in the regulation of liver glucose and lipid metabolism. As a new therapeutic strategy for metabolic diseases, the potential of using inhibitor-based therapies to fight diabetes has gained scientific momentum. PTG, a protein phosphatase, also known as glycogen targeting protein, is a member of the protein phosphatase 1 (PP1) family. It can play a role by catalyzing the dephosphorylation of phosphorylated protein molecules, especially regulating many aspects of glucose and lipid metabolism. In this review, we briefly summarize the role of PTG in glucose and lipid metabolism, and update its role in metabolic regulation, with special attention to glucose homeostasis and lipid metabolism.
Topics: Glucose; Intracellular Signaling Peptides and Proteins; Lipid Metabolism; Protein Phosphatase 1; Glycogen
PubMed: 36551183
DOI: 10.3390/biom12121755 -
International Journal of Biological... 2023Numerous mitochondrial abnormalities are reported to result from excessive inflammation during endotoxemia. Prohibitin 2 (PHB2) and phosphoglycerate mutase 5 (Pgam5)...
Numerous mitochondrial abnormalities are reported to result from excessive inflammation during endotoxemia. Prohibitin 2 (PHB2) and phosphoglycerate mutase 5 (Pgam5) have been associated with altered mitochondrial homeostasis in several cardiovascular diseases; however, their role in endotoxemia-related myocardial dysfunction has not been explored. Our experiments were aimed to evaluate the potential contribution of Pgam5 and PHB2 to endotoxemia-induced mitochondrial dysfunction in cardiomyocytes, with a focus on two endogenous protective programs that sustain mitochondrial integrity, namely mitophagy and the mitochondrial unfolded protein response (UPR). We found that PHB2 transgenic mice are resistant to endotoxemia-mediated myocardial depression and mitochondrial damage. Our assays indicated that PHB2 overexpression activates mitophagy and the UPR, which maintains mitochondrial metabolism, prevents oxidative stress injury, and enhances cardiomyocyte viability. Molecular analyses further showed that Pgam5 binds to and dephosphorylates PHB2, resulting in cytosolic translocation of mitochondrial PHB2. Silencing of Pgam5 or transfection of a phosphorylated PHB2 mutant in mouse HL-1 cardiomyocytes prevented the loss of mitochondrially-localized PHB2 and activated mitophagy and UPR in the presence of LPS. Notably, cardiomyocyte-specific deletion of Pgam5 attenuated LPS-mediated myocardial dysfunction and preserved cardiomyocyte viability. These findings suggest that Pgam5/PHB2 signaling and mitophagy/UPR are potential targets for the treatment of endotoxemia-related cardiac dysfunction.
Topics: Animals; Mice; Endotoxemia; Lipopolysaccharides; Mitophagy; Phosphoprotein Phosphatases; Prohibitins; Unfolded Protein Response
PubMed: 37781037
DOI: 10.7150/ijbs.85767 -
Journal of Cellular Physiology Aug 2023This review summarizes the implications of the primary tumor suppressor protein phosphatase and tensin homolog (PTEN) in aggressive cancer development. PTEN interacts... (Review)
Review
This review summarizes the implications of the primary tumor suppressor protein phosphatase and tensin homolog (PTEN) in aggressive cancer development. PTEN interacts with other cellular proteins or factors suggesting the existence of an intricate molecular network that regulates their oncogenic function. Accumulating evidence has shown that PTEN exists and plays a role in the cytoplasmic organelles and in the nucleus. PTEN blocks phosphoinositide 3-kinases (PI3K)-protein kinase B-mammalian target of rapamycin signaling pathway by dephosphorylating phosphatidylinositol (PI)-3,4,5-triphosphate to PI-4,5-bisphosphate thus counteracting PI3K function. Studies have shown that PTEN expression is tightly regulated at transcriptional, posttranscriptional, and posttranslational levels (including protein-protein interactions and posttranslational modifications). Despite recent advances in PTEN research, the regulation and function of the PTEN gene remain largely unknown. How mutation or loss of specific exons in the PTEN gene occurs and involves in cancer development is not clear. This review illustrates the regulatory mechanisms of PTEN expression and discusses how PTEN participates in tumor development and/or suppression. Future prospects for the clinical applications are also highlighted.
Topics: Humans; Biomarkers, Tumor; PTEN Phosphohydrolase; Proto-Oncogene Proteins c-akt; Signal Transduction; Neoplasms; Protein Processing, Post-Translational; Phosphatidylinositol 3-Kinases
PubMed: 37334436
DOI: 10.1002/jcp.31053 -
Nature Communications Apr 2023The Hsp90 molecular chaperone collaborates with the phosphorylated Cdc37 cochaperone for the folding and activation of its many client kinases. As with many kinases, the...
The Hsp90 molecular chaperone collaborates with the phosphorylated Cdc37 cochaperone for the folding and activation of its many client kinases. As with many kinases, the Hsp90 client kinase CRaf is activated by phosphorylation at specific regulatory sites. The cochaperone phosphatase PP5 dephosphorylates CRaf and Cdc37 in an Hsp90-dependent manner. Although dephosphorylating Cdc37 has been proposed as a mechanism for releasing Hsp90-bound kinases, here we show that Hsp90 bound kinases sterically inhibit Cdc37 dephosphorylation indicating kinase release must occur before Cdc37 dephosphorylation. Our cryo-EM structure of PP5 in complex with Hsp90:Cdc37:CRaf reveals how Hsp90 both activates PP5 and scaffolds its association with the bound CRaf to dephosphorylate phosphorylation sites neighboring the kinase domain. Thus, we directly show how Hsp90's role in maintaining protein homeostasis goes beyond folding and activation to include post translationally modifying its client kinases.
Topics: Humans; Cell Cycle Proteins; Protein Binding; HSP90 Heat-Shock Proteins; Molecular Chaperones
PubMed: 37069154
DOI: 10.1038/s41467-023-37659-7 -
Experimental Biology and Medicine... Mar 2022PPM1A (magnesium-dependent phosphatase 1 A, also known as PP2Cα) is a member of the Ser/Thr protein phosphatase family. Protein phosphatases catalyze the removal of... (Review)
Review
PPM1A (magnesium-dependent phosphatase 1 A, also known as PP2Cα) is a member of the Ser/Thr protein phosphatase family. Protein phosphatases catalyze the removal of phosphate groups from proteins via hydrolysis, thus opposing the role of protein kinases. The PP2C family is generally considered a negative regulator in the eukaryotic stress response pathway. PPM1A can bind and dephosphorylate various proteins and is therefore involved in the regulation of a wide range of physiological processes. It plays a crucial role in transcriptional regulation, cell proliferation, and apoptosis and has been suggested to be closely related to the occurrence and development of cancers of the lung, bladder, and breast, amongst others. Moreover, it is closely related to certain autoimmune diseases and neurodegenerative diseases. In this review, we provide an insight into currently available knowledge of PPM1A, including its structure, biological function, involvement in signaling pathways, and association with diseases. Lastly, we discuss whether PPM1A could be targeted for therapy of certain human conditions.
Topics: Apoptosis; Gene Expression Regulation; Humans; Protein Phosphatase 2C; Signal Transduction
PubMed: 34861123
DOI: 10.1177/15353702211061883 -
Molecular & Cellular Proteomics : MCP Aug 2023Protein phosphorylation is an essential regulatory mechanism that controls most cellular processes, including cell cycle progression, cell division, and response to...
Protein phosphorylation is an essential regulatory mechanism that controls most cellular processes, including cell cycle progression, cell division, and response to extracellular stimuli, among many others, and is deregulated in many diseases. Protein phosphorylation is coordinated by the opposing activities of protein kinases and protein phosphatases. In eukaryotic cells, most serine/threonine phosphorylation sites are dephosphorylated by members of the Phosphoprotein Phosphatase (PPP) family. However, we only know for a few phosphorylation sites which specific PPP dephosphorylates them. Although natural compounds such as calyculin A and okadaic acid inhibit PPPs at low nanomolar concentrations, no selective chemical PPP inhibitors exist. Here, we demonstrate the utility of endogenous tagging of genomic loci with an auxin-inducible degron (AID) as a strategy to investigate specific PPP signaling. Using Protein Phosphatase 6 (PP6) as an example, we demonstrate how rapidly inducible protein degradation can be employed to identify dephosphorylation sites and elucidate PP6 biology. Using genome editing, we introduce AID-tags into each allele of the PP6 catalytic subunit (PP6c) in DLD-1 cells expressing the auxin receptor Tir1. Upon rapid auxin-induced degradation of PP6c, we perform quantitative mass spectrometry-based proteomics and phosphoproteomics to identify PP6 substrates in mitosis. PP6 is an essential enzyme with conserved roles in mitosis and growth signaling. Consistently, we identify candidate PP6c-dependent dephosphorylation sites on proteins implicated in coordinating the mitotic cell cycle, cytoskeleton, gene expression, and mitogen-activated protein kinase (MAPK) and Hippo signaling. Finally, we demonstrate that PP6c opposes the activation of large tumor suppressor 1 (LATS1) by dephosphorylating Threonine 35 (T35) on Mps One Binder (MOB1), thereby blocking the interaction of MOB1 and LATS1. Our analyses highlight the utility of combining genome engineering, inducible degradation, and multiplexed phosphoproteomics to investigate signaling by individual PPPs on a global level, which is currently limited by the lack of tools for specific interrogation.
Topics: Humans; Proteolysis; Protein Serine-Threonine Kinases; Phosphoprotein Phosphatases; Phosphorylation; Threonine; Colorectal Neoplasms; Protein Phosphatase 2
PubMed: 37392812
DOI: 10.1016/j.mcpro.2023.100614 -
PLoS Pathogens Jul 2020Hepatitis B virus (HBV) replicates its genomic DNA via viral DNA polymerase self-primed reverse transcription of a RNA pre-genome in the nucleocapsid assembled by 120...
Hepatitis B virus (HBV) replicates its genomic DNA via viral DNA polymerase self-primed reverse transcription of a RNA pre-genome in the nucleocapsid assembled by 120 core protein (Cp) dimers. The arginine-rich carboxyl-terminal domain (CTD) of Cp plays an important role in the selective packaging of viral DNA polymerase-pregenomic (pg) RNA complex into nucleocapsid. Previous studies suggested that the CTD is initially phosphorylated at multiple sites to facilitate viral RNA packaging and subsequently dephosphorylated in association with viral DNA synthesis and secretion of DNA-containing virions. However, our recent studies suggested that Cp is hyper-phosphorylated as free dimers and its dephosphorylation is associated with pgRNA encapsidation. Herein, we provide further genetic and biochemical evidence supporting that extensive Cp dephosphorylation does take place during the assembly of pgRNA-containing nucleocapsids, but not empty capsids. Moreover, we found that cellular protein phosphatase 1 (PP1) is required for Cp dephosphorylation and pgRNA packaging. Interestingly, the PP1 catalytic subunits α and β were packaged into pgRNA-containing nucleocapsids, but not empty capsids, and treatment of HBV replicating cells with core protein allosteric modulators (CpAMs) promoted empty capsid assembly and abrogated the encapsidation of PP1 α and β. Our study thus identified PP1 as a host cellular factor that is co-packaged into HBV nucleocapsids, and plays an essential role in selective packaging of the viral DNA-polymerase-pgRNA complex through catalyzing Cp dephosphorylation.
Topics: Cell Line; Hepatitis B; Hepatitis B virus; Humans; Nucleocapsid; Peptide Fragments; Phosphorylation; Protein Phosphatase 1; RNA, Viral; Viral Core Proteins; Virus Assembly
PubMed: 32702076
DOI: 10.1371/journal.ppat.1008669