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Journal of Lipid Research Feb 2019Phosphoinositides (PIs) are recognized as major signaling molecules in many different functions of eukaryotic cells. PIs can be dephosphorylated by multiple phosphatase... (Review)
Review
Phosphoinositides (PIs) are recognized as major signaling molecules in many different functions of eukaryotic cells. PIs can be dephosphorylated by multiple phosphatase activities at the 5-, 4-, and 3- positions. Human PI 5-phosphatases belong to a family of 10 members. Except for inositol polyphosphate 5-phosphatase A, they all catalyze the dephosphorylation of PI(4,5)P and/or PI(3,4,5)P at the 5- position. PI 5-phosphatases thus directly control the levels of PI(3,4,5)P and participate in the fine-tuning regulatory mechanisms of PI(3,4)P and PI(4,5)P Second messenger functions have been demonstrated for PI(3,4)P in invadopodium maturation and lamellipodia formation. PI 5-phosphatases can use several substrates on isolated enzymes, and it has been challenging to establish their real substrate in vivo. PI(4,5)P has multiple functions in signaling, including interacting with scaffold proteins, ion channels, and cytoskeleton proteins. PI 5-phosphatase isoenzymes have been individually implicated in human diseases, such as the oculocerebrorenal syndrome of Lowe, through mechanisms that include lipid control. Oncogenic and tumor-suppressive functions of PI 5-phosphatases have also been reported in different cell contexts. The mechanisms responsible for genetic diseases and for oncogenic or tumor-suppressive functions are not fully understood. The regulation of PI 5-phosphatases is thus crucial in understanding cell functions.
Topics: Animals; Cells; Disease; Humans; Phosphatidylinositols; Phosphoric Monoester Hydrolases; Signal Transduction
PubMed: 30194087
DOI: 10.1194/jlr.R087908 -
Journal of Lipid Research Nov 2022In the yeast Saccharomyces cerevisiae, the PAH1-encoded Mg-dependent phosphatidate (PA) phosphatase Pah1 regulates the bifurcation of PA to diacylglycerol (DAG) for...
In the yeast Saccharomyces cerevisiae, the PAH1-encoded Mg-dependent phosphatidate (PA) phosphatase Pah1 regulates the bifurcation of PA to diacylglycerol (DAG) for triacylglycerol (TAG) synthesis and to CDP-DAG for phospholipid synthesis. Pah1 function is mainly regulated via control of its cellular location by phosphorylation and dephosphorylation. Pah1 phosphorylated by multiple protein kinases is sequestered in the cytosol apart from its substrate PA in the membrane. The phosphorylated Pah1 is then recruited and dephosphorylated by the protein phosphatase complex Nem1 (catalytic subunit)-Spo7 (regulatory subunit) in the endoplasmic reticulum. The dephosphorylated Pah1 hops onto and scoots along the membrane to recognize PA for its dephosphorylation to DAG. Here, we developed a proteoliposome model system that mimics the Nem1-Spo7/Pah1 phosphatase cascade to provide a tool for studying Pah1 regulation. Purified Nem1-Spo7 was reconstituted into phospholipid vesicles prepared in accordance with the phospholipid composition of the nuclear/endoplasmic reticulum membrane. The Nem1-Spo7 phosphatase reconstituted in the proteoliposomes, which were measured 60 nm in an average diameter, was catalytically active on Pah1 phosphorylated by Pho85-Pho80, and its active site was located at the external side of the phospholipid bilayer. Moreover, we determined that PA stimulated the Nem1-Spo7 activity, and the regulatory effect was governed by the nature of the phosphate headgroup but not by the fatty acyl moiety of PA. The reconstitution system for the Nem1-Spo7/Pah1 phosphatase cascade, which starts with the phosphorylation of Pah1 by Pho85-Pho80 and ends with the production of DAG, is a significant advance to understand a regulatory cascade in yeast lipid synthesis.
Topics: Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Phosphatidic Acids; Phosphoric Monoester Hydrolases; Phosphatidate Phosphatase; Membrane Proteins; Nuclear Proteins
PubMed: 36314526
DOI: 10.1016/j.jlr.2022.100282 -
Stress-mediated generation of deleterious ROS in healthy individuals - role of cytochrome c oxidase.Journal of Molecular Medicine (Berlin,... May 2020Psychosocial stress is known to cause an increased incidence of coronary heart disease. In addition, multiple other diseases like cancer and diabetes mellitus have been... (Review)
Review
Psychosocial stress is known to cause an increased incidence of coronary heart disease. In addition, multiple other diseases like cancer and diabetes mellitus have been related to stress and are mainly based on excessive formation of reactive oxygen species (ROS) in mitochondria. The molecular interactions between stress and ROS, however, are still unknown. Here we describe the missing molecular link between stress and an increased cellular ROS, based on the regulation of cytochrome c oxidase (COX). In normal healthy cells, the "allosteric ATP inhibition of COX" decreases the oxygen uptake of mitochondria at high ATP/ADP ratios and keeps the mitochondrial membrane potential (ΔΨ) low. Above ΔΨ values of 140 mV, the production of ROS in mitochondria increases exponentially. Stress signals like hypoxia, stress hormones, and high glutamate or glucose in neurons increase the cytosolic Ca concentration which activates a mitochondrial phosphatase that dephosphorylates COX. This dephosphorylated COX exhibits no allosteric ATP inhibition; consequently, an increase of ΔΨ and ROS formation takes place. The excess production of mitochondrial ROS causes apoptosis or multiple diseases.
Topics: Adenosine Triphosphate; Animals; Biomarkers; Calcium; Electron Transport Complex IV; Humans; Membrane Potential, Mitochondrial; Mitochondria; Prostaglandin-Endoperoxide Synthases; Reactive Oxygen Species; Signal Transduction; Stress, Physiological; Stress, Psychological
PubMed: 32313986
DOI: 10.1007/s00109-020-01905-y -
Journal of Cancer Research and Clinical... Jan 2022Cyclase-associated protein 1 (CAP1) is a ubiquitous protein which regulates actin dynamics. Previous studies have shown that S308 and S310 are the two major...
PURPOSE
Cyclase-associated protein 1 (CAP1) is a ubiquitous protein which regulates actin dynamics. Previous studies have shown that S308 and S310 are the two major phosphorylated sites in human CAP1. In the present study, we aimed to investigate the role of CAP1 phosphorylation in lung cancer.
METHODS
Massive bioinformatics analysis was applied to determine CAP1's role in different cancers and especially in lung cancer. Lung cancer patients' serum and tissue were collected and analyzed in consideration of clinical background. CAP1 shRNA-lentivirus and siRNA were applied to CAP1 gene knockdown, and plasmids were constructed for CAP1 phosphorylation and de-phosphorylation. Microarray analysis was used for CAP1-associated difference analysis. Both in vitro and in vivo experiments were performed to investigate the roles of CAP1 phosphorylation and de-phosphorylation in lung cancer A549 cells.
RESULTS
CAP1 is a kind of cancer-related protein. Its mRNA was overexpressed in most types of cancer tissues when compared with normal tissues. CAP1 high expression correlated with poor prognosis. Our results showed that serum CAP1 protein concentrations were significantly upregulated in non-small cell lung cancer (NSCLC) patients when compared with the healthy control group, higher serum CAP1 protein concentration correlated with shorter overall survival (OS) in NSCLC patients, and higher pCAP1 and CAP1 protein level were observed in lung cancer patients' tumor tissue compared with adjacent normal tissue. Knockdown CAP1 in A549 cells can inhibit proliferation and migration, and the effect is validated in H1975 cells. It can also lead to an increase ratio of F-actin/G-actin. In addition, phosphorylated S308 and S310 in CAP1 promoted lung cancer cell proliferation, migration, and metastasis both in vitro and in vivo. When de-phosphorylated, these two sites in CAP1 showed the opposite effect. Phosphorylation of CAP1 can promote epithelial-mesenchymal transition (EMT).
CONCLUSION
These findings indicated that CAP1 phosphorylation can promote lung cancer proliferation, migration, and invasion. Phosphorylation sites of CAP1 might be a novel target for lung cancer treatment.
Topics: A549 Cells; Aged; Animals; Carcinoma, Non-Small-Cell Lung; Cell Cycle Proteins; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cytoskeletal Proteins; Epithelial-Mesenchymal Transition; Female; Humans; Lung Neoplasms; Male; Mice; Mice, Nude; Neoplasm Invasiveness; Neoplasm Transplantation; Phosphorylation; RNA Interference; RNA, Small Interfering; Transplantation, Heterologous
PubMed: 34636991
DOI: 10.1007/s00432-021-03819-9 -
Cell Discovery Jul 2023How cells adapt their gene expression to nutritional changes remains poorly understood. Histone H3T11 is phosphorylated by pyruvate kinase to repress gene transcription....
How cells adapt their gene expression to nutritional changes remains poorly understood. Histone H3T11 is phosphorylated by pyruvate kinase to repress gene transcription. Here, we identify the protein phosphatase 1 (PP1), Glc7 as the enzyme that specifically dephosphorylates H3T11. We also characterize two novel Glc7-containing complexes and reveal their roles in regulating gene expression upon glucose starvation. Specifically, the Glc7-Sen1 complex dephosphorylates H3T11 to activate the transcription of autophagy-related genes. The Glc7-Rif1-Rap1 complex dephosphorylates H3T11 to derepress the transcription of telomere-proximal genes. Upon glucose starvation, Glc7 expression is up-regulated and more Glc7 translocates into the nucleus to dephosphorylate H3T11, leading to induction of autophagy and derepressed transcription of telomere-proximal genes. Furthermore, the functions of PP1/Glc7 and the two Glc7-containing complexes are conserved in mammals to regulate autophagy and telomere structure. Collectively, our results reveal a novel mechanism that regulate gene expression and chromatin structure in response to glucose availability.
PubMed: 37433812
DOI: 10.1038/s41421-023-00551-1 -
Nature Communications Feb 2024Osteoclasts are over-activated as we age, which results in bone loss. Src deficiency in mice leads to severe osteopetrosis due to a functional defect in osteoclasts,...
Osteoclasts are over-activated as we age, which results in bone loss. Src deficiency in mice leads to severe osteopetrosis due to a functional defect in osteoclasts, indicating that Src function is essential in osteoclasts. G-protein-coupled receptors (GPCRs) are the targets for ∼35% of approved drugs but it is still unclear how GPCRs regulate Src kinase activity. Here, we reveal that GPR54 activation by its natural ligand Kisspeptin-10 (Kp-10) causes Dusp18 to dephosphorylate Src at Tyr 416. Mechanistically, Gpr54 recruits both active Src and the Dusp18 phosphatase at its proline/arginine-rich motif in its C terminus. We show that Kp-10 binding to Gpr54 leads to the up-regulation of Dusp18. Kiss1, Gpr54 and Dusp18 knockout mice all exhibit osteoclast hyperactivation and bone loss, and Kp-10 abrogated bone loss by suppressing osteoclast activity in vivo. Therefore, Kp-10/Gpr54 is a promising therapeutic target to abrogate bone resorption by Dusp18-mediated Src dephosphorylation.
Topics: Animals; Mice; Osteoclasts; Kisspeptins; Receptors, G-Protein-Coupled; src-Family Kinases; Mice, Knockout; Bone Resorption; Receptors, Kisspeptin-1
PubMed: 38346942
DOI: 10.1038/s41467-024-44852-9 -
Angewandte Chemie (International Ed. in... Nov 2022Herein, we show intranuclear nanoribbons formed upon dephosphorylation of leucine-rich L- or D-phosphopeptide catalyzed by alkaline phosphatase (ALP) to selectively kill...
Herein, we show intranuclear nanoribbons formed upon dephosphorylation of leucine-rich L- or D-phosphopeptide catalyzed by alkaline phosphatase (ALP) to selectively kill osteosarcoma cells. Being dephosphorylated by ALP, the peptides are first transformed into micelles and then converted into nanoribbons. The peptides/assemblies first aggregate on cell membranes, then enter cells via endocytosis, and finally accumulate in nuclei (mainly in nucleoli). Proteomics analysis suggests that the assemblies interact with histone proteins. The peptides kill osteosarcoma cells rapidly and are nontoxic to normal cells. Moreover, the repeated stimulation of the osteosarcoma cells by the peptides sensitizes the cancer cells rather than inducing resistance. This work not only illustrates a novel mechanism for nucleus targeting, but may also pave a new way for selectively killing osteosarcoma cells and minimizing drug resistance.
Topics: Humans; Alkaline Phosphatase; Nanotubes, Carbon; Micelles; Phosphopeptides; Histones; Leucine; Osteosarcoma; Cell Line, Tumor; Bone Neoplasms
PubMed: 36102872
DOI: 10.1002/anie.202210568 -
International Journal of Molecular... Dec 2019Protein phosphorylation affects conformational change, interaction, catalytic activity, and subcellular localization of proteins. Because the post-modification of... (Review)
Review
Protein phosphorylation affects conformational change, interaction, catalytic activity, and subcellular localization of proteins. Because the post-modification of proteins regulates diverse cellular signaling pathways, the precise control of phosphorylation states is essential for maintaining cellular homeostasis. Kinases function as phosphorylating enzymes, and phosphatases dephosphorylate their target substrates, typically in a much shorter time. The c-Jun N-terminal kinase (JNK) signaling pathway, a mitogen-activated protein kinase pathway, is regulated by a cascade of kinases and in turn regulates other physiological processes, such as cell differentiation, apoptosis, neuronal functions, and embryonic development. However, the activation of the JNK pathway is also implicated in human pathologies such as cancer, neurodegenerative diseases, and inflammatory diseases. Therefore, the proper balance between activation and inactivation of the JNK pathway needs to be tightly regulated. Dual specificity phosphatases (DUSPs) regulate the magnitude and duration of signal transduction of the JNK pathway by dephosphorylating their substrates. In this review, we will discuss the dynamics of phosphorylation/dephosphorylation, the mechanism of JNK pathway regulation by DUSPs, and the new possibilities of targeting DUSPs in JNK-related diseases elucidated in recent studies.
Topics: Animals; Dual-Specificity Phosphatases; Humans; JNK Mitogen-Activated Protein Kinases; Mitogen-Activated Protein Kinases; Models, Biological; Phosphorylation; Signal Transduction
PubMed: 31817617
DOI: 10.3390/ijms20246157 -
Frontiers in Pharmacology 2023The energy imbalance when energy intake exceeds expenditure acts as an essential factor in the development of insulin resistance (IR). The activity of brown adipose...
The energy imbalance when energy intake exceeds expenditure acts as an essential factor in the development of insulin resistance (IR). The activity of brown adipose tissue, which is involved in the dissipation of energy via heat expenditure decreases under type 2 diabetic mellitus (T2DM) state when the number of pathological aging adipocytes increases. Protein tyrosine phosphatase non-receptor type 2 (PTPN2) regulates several biological processes by dephosphorylating several cellular substrates; however, whether PTPN2 regulates cellular senescence in adipocytes and the underlying mechanism has not been reported. We constructed a model of type 2 diabetic mice with PTPN2 overexpression to explore the role of PTPN2 in T2DM. We revealed that PTPN2 facilitated adipose tissue browning by alleviating pathological senescence, thus improving glucose tolerance and IR in T2DM. Mechanistically, we are the first to report that PTPN2 could bind with transforming growth factor-activated kinase 1 (TAK1) directly for dephosphorylation to inhibit the downstream MAPK/NF-κB pathway in adipocytes and regulate cellular senescence and the browning process subsequently. Our study revealed a critical mechanism of adipocytes browning progression and provided a potential target for the treatment of related diseases.
PubMed: 37251330
DOI: 10.3389/fphar.2023.1124633 -
Biochimica Et Biophysica Acta.... Jun 2021PGAM5 is a protein phosphatase located in the inner mitochondrial membrane through its transmembrane (TM) domain and is cleaved within the TM domain upon mitochondrial...
PGAM5 is a protein phosphatase located in the inner mitochondrial membrane through its transmembrane (TM) domain and is cleaved within the TM domain upon mitochondrial dysfunction. We found previously that cleaved PGAM5 is released from mitochondria, following proteasome-mediated rupture of the outer mitochondrial membrane during mitophagy, a selective form of autophagy specific to mitochondria. Here, we examined the role of cleaved PGAM5 outside mitochondria. Deletion mutants that mimic cleaved PGAM5 existed not only in the cytosol but also in the nucleus, and a fraction of cleaved PGAM5 translocated to the nucleus during mitophagy induced by the uncoupler CCCP. We identified serine/arginine-related nuclear matrix protein of 160 kDa (SRm160)/SRRM1, which contains a highly phosphorylated domain rich in arginine/serine dipeptides, called the RS domain, as a nuclear protein that interacts with PGAM5. PGAM5 dephosphorylated SRm160, and incubation of lysates from WT cells, but not of those from PGAM5-deficient cells, induced dephosphorylation of SRm160 and another RS domain-containing protein SRSF1, one of the most characterized serine/arginine-rich (SR) proteins. Moreover, phosphorylation of these proteins and other SR proteins, which are commonly reactive toward the 1H4 monoclonal antibody that detects phosphorylated SR proteins, decreased during mitophagy, largely because of PGAM5 activity. These results suggest that PGAM5 regulates phosphorylation of these nuclear proteins during mitophagy. Because SRm160 and SR proteins play critical roles in mRNA metabolism, PGAM5 may coordinate cellular responses to mitochondrial stress at least in part through post-transcriptional and pre-translational events.
Topics: Antigens, Nuclear; Cell Nucleus; Cytosol; HeLa Cells; Humans; Membrane Proteins; Mitochondria; Mitochondrial Membrane Transport Proteins; Mitochondrial Membranes; Mitochondrial Proteins; Mitophagy; Nuclear Matrix-Associated Proteins; Phosphoprotein Phosphatases; Phosphorylation; RNA-Binding Proteins; Serine-Arginine Splicing Factors; Ubiquitin-Protein Ligases
PubMed: 33872670
DOI: 10.1016/j.bbamcr.2021.119045