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At least 19 recordsLinked to original sources
PubMed1977

Specificity of a protein phosphatase inhibitor from rabbit skeletal muscle.

A hear-stable protein, which is a specific inhibitor of protein phosphatase-III, was purified 700-fold from skeletal muscle by a procedure that involved heat-treatment at 95 degrees C, chromatography on DEAE-cellulose and gel filtration on Sephadex G-100. The final step completely resolved the protein phosphatase inhibitor from the protein inhibitor of cyclic AMP-dependent protein kinase. The phosphorylase phosphatase, beta-phosphorylase kinase phosphatase, glycogen synthase phosphatase-1 and glycogen synthase phosphatase-2 activities of protein phosphatase-III [Antoniw, J. F., Nimmo, H. G., Yeaman, S. J. & Cohen, P.(1977) Biochem.J. 162, 423-433] were inhibited in a very similar manner by the protein phosphatase inhibitor and at least 95% inhibition was observed at high concentrations of inhibitor. The two forms of protein phosphatase-III, termed IIIA and IIIB, were equally susceptible to the protein phosphatase inhibitor. The protein phosphatase inhibitor was at least 200 times less effective in inhibiting the activity of protein phosphatase-I and protein phosphatase-II. The high degree of specificity of the inhibitor for protein phosphatase-III was used to show that 90% of the phosphorylase phosphatase and glycogen synthase phosphatase activities measured in muscle extracts are catalysed by protein phosphatase-III. Protein phosphatase-III was tightly associated with the protein-glycogen complex that can be isolated from skeletal muscle, whereas the protein phosphatase inhibitor and protein phosphatase-II were not. The results provide further evidence that the enzyme that catalyses the dephosphorylation of the alpha-subunit of phosphorylase kinase (protein phosphatase-II) and the enzyme that catalyses the dephosphorylation of the beta-subunit of phosphorylase kinase (protein phosphatase-III) are distinct. The results suggest that the protein phosphatase inhibitor may be a useful probe for differentiating different classes of protein phosphatases in mammalian cells.

Animals↗
PubMed1975

Purification of bisphosphoglyceromutase, 2,3-bisphosphoglycerate phosphatase and phosphoglyceromutase from human erthrocytes. Three enzyme activities in one protein.

Bisphosphoglyceromutase, 2,3-bisphosphoglycerate phosphatase and phosphoglyceromutase have been purified from human red cells. Three enzymes were co-purified throughout all purification steps. Three fractions (peaks I, II and III) which were chromatographically separable and had three activities in different ratios were obtained. Peak III which contained the main bisphosphoglyceromutase and 2,3-bisphosphoglycerate phosphatase activities was purified to homogeneity by electrophoretic and ultracentrifugal analyses. The homogeneous preparation had the phosphoglyceromutase activity. The three activities were lost at the same rate during thermal inactivation. Thus, bisphosphoglyceromutase and 2,3-bisphosphoglycerate phosphatase activities, which are responsible for 2,3-bisphosphoglycerate metabolism in red cells, are displayed by the same enzyme protein which has phosphoglyceromutase activity. Peaks I and II were rich in the phosphoglyceromutase activity. Both peaks showed bisphosphoglyceromutase and 2,3-bisphosphoglycerate phosphatase activities, although these two activities were much smaller than those of peak III. Some of the enzymic properties of peak III are described. Comparative studies on three peaks showed that the phosphoglyceromutase of peak III differed from that of peaks I and II in the kinetic property and thermostability.

Chromatography↗
PubMed2022

WNK1-OSR1 Signaling Regulates Angiogenesis-Mediated Metastasis towards Developing a Combinatorial Anti-Cancer Strategy.

Lysine-deficient protein kinase-1 (WNK1) is critical for both embryonic angiogenesis and tumor-induced angiogenesis. However, the downstream effectors of WNK1 during these processes remain ambiguous. In this study, we identified that oxidative stress responsive 1b (osr1b) is upregulated in endothelial cells in both embryonic and tumor-induced angiogenesis in zebrafish, accompanied by downregulation of protein phosphatase 2A (pp2a) subunit ppp2r1bb. In addition, wnk1a and osr1b are upregulated in two liver cancer transgenic fish models: [tert x p53-/-] and [HBx,src,p53-/-,RPIA], while ppp2r1bb is downregulated in [tert x p53-/-]. Furthermore, using HUVEC endothelial cells co-cultured with HepG2 hepatoma cells, we confirmed that WNK1 plays a critical role in the induction of hepatoma cell migration in both endothelial cells and hepatoma cells. Moreover, overexpression of OSR1 can rescue the reduced cell migration caused by shWNK1 knockdown in HUVEC cells, indicating OSR1 is downstream of WNK1 in endothelial cells promoting hepatoma cell migration. Overexpression of PPP2R1A can rescue the increased cell migration caused by WNK1 overexpression in HepG2, indicating that PPP2R1A is a downstream effector in hepatoma. The combinatorial treatment with WNK1 inhibitor (WNK463) and OSR1 inhibitor (Rafoxanide) plus oligo-fucoidan via oral gavage to feed [HBx,src,p53-/-,RPIA] transgenic fish exhibits much more significant anticancer efficacy than Regorafenib for advanced HCC. Importantly, oligo-fucoidan can reduce the cell senescence marker-IL-1β expression. Furthermore, oligo-fucoidan reduces the increased cell senescence-associated β-galactosidase activity in tert transgenic fish treated with WNK1-OSR1 inhibitors. Our results reveal the WNK1-OSR1-PPP2R1A axis plays a critical role in both endothelial and hepatoma cells during tumor-induced angiogenesis promoting cancer cell migration. By in vitro and in vivo experiments, we further uncover the molecular mechanisms of WNK1 and its downstream effectors during tumor-induced angiogenesis. Targeting WNK1-OSR1-mediated anti-angiogenesis and anti-cancer activity, the undesired inflammation response caused by inhibiting WNK1-OSR1 can be attenuated by the combination therapy with oligo-fucoidan and may improve the efficacy.

Animals↗
PubMed2026

NAP1 switches from an activator to a limiter of interferon induction by trapping TBK1 in condensates.

TBK1 kinase is a central regulator of type I IFN production. Upon activation of the IFN-β induction pathway, TBK1-adaptor proteins (NAP1, SINTBAD, TANK) form liquid condensates. We show that NAP1 condensates concentrate TBK1. Using NAP1KO cell lines, we demonstrate that NAP1 exerts a dual effect on TBK1 activity. Initially, NAP1 binds TBK1 and increases its activity, promoting IFN pathway activation. Subsequently, TBK1-mediated phosphorylation of NAP1 induces the formation of condensates. These NAP1 condensates concentrate both TBK1 and the phosphatase PP2A, which dephosphorylates and consequently deactivates TBK1, thus limiting IFN induction. Additionally, in patients with lupus or interferonopathies, we identify NAP1 variants unable to form condensates upon danger signal exposure, which sustain TBK1 activation without limiting its activity. This study reveals a mode of regulating a signaling pathway through condensate formation and provides a potential molecular explanation for immune dysregulation associated with NAP1 variants in certain patients with interferonopathies.

Protein Serine-Threonine Kinases↗
PubMed1977

Comparison of the substrate specificities of protein phosphatases involved in the regulation of glycogen metabolism in rabbit skeletal muscle.

Muscle extracts were subjected to fractionation with ethanol, chromatography on DEAE-cellulose, precipitation with (NH4)2SO4 and gel filtration on Sephadex G-200. These fractions were assayed for protein phosphatase activities by using the following seven phosphoprotein substrates: phosphorylase a, glycogen synthase b1, glycogen synthase b2, phosphorylase kinase (phosphorylated in either the alpha-subunit or the beta-subunit), histone H1 and histone H2B. Three protein phosphatases with distinctive specificities were resolved by the final gel-filtration step and were termed I, II and III. Protein phosphatase-I, apparent mol.wt. 300000, was an active histone phosphatase, but it accounted for only 10-15% of the glycogen synthase phosphatase-1 and glycogen synthase phosphatase-2 activities and 2-3% of the phosphorylase kinase phosphatase and phosphorylase phosphatase activity recovered from the Sephadex G-200 column. Protein phosphatase-II, apparent mol.wt. 170000, possessed histone phosphatase activity similar to that of protein phosphatase-I. It possessed more than 95% of the activity towards the alpha-subunit of phosphorylase kinase that was recovered from Sephadex G-200. It accounted for 10-15% of the glycogen synthase phosphatase-1 and glycogen synthase phosphatase-2 activity, but less than 5% of the activity against the beta-subunit of phosphorylase kinase and 1-2% of the phosphorylase phosphatase activity recovered from Sephadex G-200. Protein phosphatase-III was the most active histone phosphatase. It possessed 95% of the phosphorylase phosphatase and beta-phosphorylase kinase phosphatase activities, and 75% of the glycogen synthase phosphatase-1 and glycogen synthase phosphatase-2 activities recovered from Sephadex G-200. It accounted for less than 5% of the alpha-phosphorylase kinase phosphatase activity. Protein phosphatase-III was sometimes eluted from Sephadex-G-200 as a species of apparent mol.wt. 75000(termed IIIA), sometimes as a species of mol.wt. 46000(termed IIIB) and sometimes as a mixture of both components. The substrate specificities of protein phosphatases-IIA and -IIB were identical. These findings, taken with the observation that phosphorylase phosphatase, beta-phosphorylase kinase phosphatase, glycogen synthase phosphatase-1 and glycogen synthase phosphatase-2 activities co-purified up to the Sephadex G-200 step, suggest that a single protein phosphatase (protein phosphatase-III) catalyses each of the dephosphorylation reactions that inhibit glycogenolysis or stimulate glycogen synthesis. This contention is further supported by results presented in the following paper [Cohen, P., Nimmo, G.A. & Antoniw, J.F. (1977) Biochem. J. 1628 435-444] which describes a heat-stable protein that is a specific inhibitor of protein phosphatase-III.

Animals↗
PubMed2026

Cdk1 and PP2A constitute a molecular switch controlling orderly degradation of atypical E2Fs.

Dynamic oscillations in the phosphorylation and ubiquitination of key proliferative regulators are defining features of the eukaryotic cell cycle. Resetting the cell cycle at the mitosis-to-G1 transition requires activation of the E3 ubiquitin ligase Anaphase-Promoting Complex/Cyclosome (APC/C), which ensures cell cycle irreversibility by targeting dozens of substrates for degradation, safeguarding genome integrity. However, the overall coupling of substrate phosphorylation with target recognition and degradation by the APC/C remains relatively unexplored. As a paradigm for further defining these rules, we focused on E2F7 and E2F8-atypical E2F-family proteins that coordinate cell cycle gene expression by restraining the pro-proliferative transcriptional activity of E2F1. Leveraging complementary cell and cell-free systems, we demonstrate that flexible domains at the amino-termini of E2F7 and E2F8 contain APC/C recognition motifs adjacent to critical Thr residues, whose phosphorylation by Cdk1 is rate-limiting for degradation. The removal of this phosphorylation by PP2A serves as a molecular switch, coupling the degradation of E2F7 and E2F8 to the G1 phase, coinciding with the rise of E2F1. Collectively, these findings highlight a critical role for Cdk1-PP2A signaling in controlling the orderly degradation of APC/C substrates, ensuring precisely timed assembly of the transcriptional infrastructure that coordinates cell cycle commitment and progression.

Protein Phosphatase 2↗
PubMed1975

Effect of various concentrations of protein in chick diet upon the metabolic enzymes of glycine and serine.

The effect of feeding low protein diets with and without 2% glycine or 2% L-serine to chicks upon the enzymes concerned in the matabolism of glycine and serine has been determined. D-3-phosphoglycerate dehydrogenase (EC 1.1.1.s), hosphoserine phosphatase (EC 3.1.3.3), and serine hydroxymethyltransferase (EC 2.1.2.1) activities were significantly increased in livers from chicks fed 75% protein diets as compared to liver enzyme activities from chicks fed either 24% chick starter, 2% or 25% protein diets. Phosphoserine phosphatase activity was significantly higher in kidney tissue of chicks fed 75% protein diets. Livers from chicks fed 25% protein diets had a higher activity for D-3-phosphoglycerate dehydrogenase and phosphoserine phosphatase than did those fed chick starter or 2% protein diets. D-3-phosphoglycerate dehydrogenase and phosphoserine phosphatase activities were higher in livers from chicks fed 2% protein, 2% protein + 2% glycine, and 2% protein + 2% L-serine diets when compared to those from chicks fed low protein diets with supplemental methionine or cysteine. Serine dehydratase (EC 4.2.1.13), glycerate dehydrogenase (EC 1.1.1.29) and hydroxypyruvate-P: L-glutamate transaminase activities remained constant in livers from chicks fed all experimental diets. The uric acid concentration was significantly increased in plasma from chicks fed the high protein diets which suggests that D-3-phosphoglycerate dehydrogenase, phosphoserine phosphatase and serine hydroxymethyltransferase activities were increased because of the high requirement for glycine in uric acid formation. The 75% protein diet provided three times as much glycine as the 25% protein diet which may have met the increased need for glycine for uric acid formation.

Alcohol Oxidoreductases↗
PubMed2026

Proteomic signatures for sudden cardiac death and related intermediate phenotypes.

BACKGROUND: Novel markers for sudden cardiac death (SCD) are needed. OBJECTIVE: This study aimed to explore whether a protein risk score derived from a large-scale proteomics dataset improves risk prediction of SCD in the general population. METHODS: A total of 52,705 individuals with 1459 unique plasma protein measurements were included from the UK Biobank Pharma Proteomics Project. A protein risk score was developed using lasso-penalized Cox regression on 40,722 participants enrolled at the English centers and validated on 11,983 participants enrolled at the remaining centers. RESULTS: The protein risk score formula developed from the derivation set comprised 64 unique plasma proteins including latent-transforming growth factor beta-binding protein 2, protein tyrosine phosphatase receptor sigma, and spondin-1. In the test set, a per standard deviation increase in protein risk score was associated with a hazard ratio of 2.60 (95% confidence interval [CI] 2.12-3.18) for SCD. Adding a protein risk score to SCD clinical risk factors resulted in a concordance index increase of 0.063 (95% CI 0.037-0.105) for SCD. For ventricular arrhythmia-mediated SCDs, an increase in concordance index when a protein risk score was added to SCD clinical risk factors was 0.070 (95% CI 0.010-0.188). A protein risk score added to SCD clinical risk factors resulted in a risk reclassification of 16.9% (95% CI 9.0-24.7) at a 10-year risk threshold of 5%. A protein risk score was significantly associated with intermediate phenotypes of SCD including corrected QT prolongation, an increase in left ventricular mean myocardial thickness, and a decrease in left ventricular global longitudinal strain. CONCLUSION: A protein risk score derived from a single plasma sample significantly improved risk prediction of SCD and related intermediate phenotypes.

Humans↗
PubMed2026

Distinct STRIPAK subunits drive conserved and subunit-specific signaling programs in Cryptococcus neoformans.

The striatin-interacting phosphatase and kinase (STRIPAK) complex is a conserved protein phosphatase 2A (PP2A)-associated signaling hub that integrates kinase-phosphatase networks, yet its roles in human fungal pathogens remain poorly defined. Here, we dissected STRIPAK functions in the opportunistic pathogen Cryptococcus neoformans by combining genetic, genomic, virulence, and phosphoproteomic analyses across mutants lacking individual STRIPAK subunits. Loss of the core STRIPAK components via PPH22, FAR8, FAR9, or FAR11 mutations caused severe defects in growth, stress adaptation, cell cycle progression, and morphogenesis, accompanied by widespread aneuploidy and genome instability. In murine infection models, far11Δ strains were avirulent, whereas far9Δ mutants caused delayed but ultimately fatal disease and underwent host-associated genome remodeling, with recovered isolates exhibiting chromosome 11 amplification despite no consistent in vitro fitness advantage. In contrast, deletion of MOB3 produced a hypervirulent phenotype. mob3Δ cells exhibited enhanced transmigration across an in vitro blood-brain barrier model, increased survival in macrophages, and generated small-cell morphotypes, features associated with increased dissemination. Phosphoproteomic profiling revealed extensive and overlapping phosphorylation changes among core STRIPAK mutants, affecting pathways involved in signaling, cytoskeletal, cell cycle control, chromatin regulation, RNA metabolism, and stress responses. Conversely, mob3Δ mutants displayed a smaller, largely distinct phosphoproteomic signature. Network and functional enrichment analyses highlighted STRIPAK-dependent regulation of TORC2-associated signaling, MAPK/GTPase signaling, autophagy, nuclear transport, RNA processing, DNA replication, and ribosome biogenesis. Together, these findings establish STRIPAK as a coordinator of genome stability, morphological plasticity, stress adaptation, and virulence in C. neoformans, and demonstrate that individual STRIPAK subunits drive shared yet divergent signaling outputs that shape host-pathogen interactions.IMPORTANCEFungal pathogens must rapidly adapt their growth, morphology, and stress responses to survive within the host, requiring precise coordination of cellular signaling pathways. The conserved striatin-interacting phosphatase and kinase (STRIPAK) complex controls key developmental programs in eukaryotes, but its roles in fungal pathogenesis are not fully defined. We previously showed that STRIPAK is important for genome stability, development, and virulence in the opportunistic human fungal pathogen Cryptococcus neoformans. Here, we define how individual STRIPAK subunits differentially regulate fungal morphogenesis, genome plasticity, host adaptation, and virulence, revealing both shared and subunit-specific functions within this conserved signaling complex. Core STRIPAK mutants exhibit severe growth and stress-response defects and attenuation of virulence, whereas loss of the Mob3 subunit promotes hypervirulence by enhancing dissemination and persistence within the host. Phosphoproteomic profiling reveals that individual STRIPAK components exert shared yet distinct control over phosphorylation networks that shape host-pathogen interactions, establishing STRIPAK as a central signaling hub and a potential target for antifungal intervention.

Cryptococcus neoformans↗
PubMed2026

The tumor suppressor NDRG2 recruits protein phosphatase 2A to suppress STAT5 phosphorylation in adult T-cell leukemia/lymphoma.

Adult T-cell leukemia/lymphoma (ATL) is an aggressive T-cell malignancy with a poor prognosis that is caused by human T-cell leukemia virus type 1 infection. We previously demonstrated that N-myc downstream-regulated gene 2 (NDRG2) is significantly downregulated in ATL, resulting in aberrant activation of the signal transduction pathways through the dissociation of serine/threonine protein phosphatase 2A. To identify potential targets of NDRG2, we performed comprehensive mass spectrometry of differentially phosphorylated peptides in ATL cells with overexpression of NDRG2 using a TiO2-based enrichment method. Kyoto Encyclopedia of Genes and Genomes and gene ontology analysis revealed that the downregulated phosphopeptides correlated with signaling pathways, T-cell differentiation, and proliferation. Our results identified signal transducer and activator of transcription 5B as a novel NDRG2-regulated protein that is dephosphorylated at serine 193 and tyrosine 699. Although enforced expression of NDRG2 in ATL cell lines does not change the phosphorylation of Janus kinase 3, an upstream regulator of STAT5, phosphorylated STAT5 at tyrosine and serine is significantly suppressed by the direct binding to STAT5 with NDRG2 leading to the inhibition of STAT5 downstream gene expression. Furthermore, NDRG2 binds to STAT5B with alanine replacement of Y699 (Y699A), but only weakly associates with S193A, suggesting that NDRG2 is directly involved in serine phosphorylation through the recruitment of serine/threonine protein phosphatase 2A to STAT5. Because S193 A remarkably induces reduced phosphorylation of Y699 and subsequent transcriptional activity, the induction of serine phosphorylation through the loss of NDRG2 expression is dispensable for STAT5 tyrosine phosphorylation and activity. Since the loss of NDRG2 expression is essential factor to maintenance of ATL cells by STAT5 activity through phosphorylation of serine and tyrosine, targeting STAT5 becomes a feasible and effective strategy in NDRG2-deficient ATL.

Humans↗
PubMed1975

Characterization of soluble and microsomal adenosine 3',5'-monophosphate-dependent protein kinases from rabbit heart.

Cardiac microsomes contained an intrinsic adenosine 3',5'-monophosphate (cyclic AMP)-dependent protein kinase which stimulated phosphorylation of serine residue(s) of microsomal protein. The phosphorylated residues were associated with a microsomal protein component of 20,000 molecular weight as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Intrinsic phosphoprotein phosphatase activity of the microsomal membrane resulted in rapid dephosphorylation of these residues. Microsomes phosphorylated in the presence of cyclic AMP (10(-6) M) exhibited enhanced calcium uptake. We conclude that: 1) cardiac microsomes contain intrinsic cyclic AMP-dependent protein kinase(s) which phosphorylate a specific microsomal protein and phosphoprotein phosphatase(s) capable of dephosphorylating this protein, 2) phosphorylation of this protein enhances calcium uptake, 3) reversible phosphorylation of microsomal membrane may be an important mechanism for the regulation of calcium uptake of cardiac microsomes by cyclic AMP.

Animals↗
PubMed2026

Druggable genome CRISPRi screen in hydrogels reveals regulators of cortactin-driven actin remodeling promoting glioblastoma invasion.

To identify therapeutic targets limiting glioblastoma invasion, we applied druggable genome CRISPRi screens and multiomic analysis to patient-derived glioblastoma cells in micro-dissectible biomimetic 3D hydrogels that permitted separation and analysis of core versus invasive fractions. Of 2,550 genes screened, 12 encoded druggable targets whose suppression limited invasion, of which AURKB (encoding aurora kinase B) and ACP1 (encoding low molecular weight protein tyrosine phosphatase, LMW-PTP) were validated in neurosphere assays and in vivo. Proximity labeling identified cortactin as a link between LMW-PTP and aurora B, and we observed that cortactin underwent serine phosphorylation by aurora B and tyrosine dephosphorylation by LMW-PTP. Targeting ACP1 or AURKB via CRISPRi or inhibitors in culture and in vivo shifted the cortactin phosphorylation balance in glioblastoma, reducing levels of cortactin and the actin-related protein 2/3 (Arp2/3) complex that mediates cortactin-induced actin stabilization, thereby reducing actin-cortactin-Arp2/3 colocalization and subsequent actin polymerization. AURKB or ACP1 targeting shifted actin from cytoplasm to the nucleus, reducing mesenchymal gene expression. Biophysical analysis implicated AURKB in glioblastoma cell adhesion and stiffness needed for initial migration and ACP1 in mechanical stress resistance required for later migration. These findings revealed a targetable axis balancing kinase and phosphatase activities to regulate actin polymerization during glioblastoma invasion.

Humans↗
PubMed1979

Characterization and regulation of reductase kinase, a protein kinase that modulates the enzymic activity of 3-hydroxy-3-methylglutaryl-coenzyme A reductase.

The activity of rat liver 3-hydroxy-3-methylglutaryl-coenzyme A reductase [HMG-CoA reductase; mevalonate:NADP(+) oxidoreductase (CoA-acylating), EC 1.1.1.34] can be modulated in vitro by a phosphorylation-dephosphorylation reaction sequence. A microsomal reductase kinase catalyzes the phosphorylation of HMG-CoA reductase and histones. Histone phosphorylation was enhanced 2- to 3-fold by cyclic AMP. Reductase kinase exists in interconvertible active and inactive forms. Incubation of reductase kinase with phosphoprotein phosphatase resulted in a time-dependent decrease in the ability of reductase kinase to catalyze the phosphorylation of histones and to inactivate HMG-CoA reductase. Incubation of phosphoprotein phosphatase-inactivated reductase kinase with [gamma-(32)P]ATP plus Mg(2+) and a partially purified protein kinase designated reductase kinase kinase resulted in parallel increases in protein-bound (32)P radioactivity and ability to inactivate HMG-CoA reductase. Incubation of (32)P-labeled reductase kinase with phosphoprotein phosphatase resulted in a time-dependent loss of protein-bound (32)P radioactivity and a decrease in the ability to inactivate HMG-CoA reductase. Polyacrylamide gel electrophoresis of purified reductase kinase incubated with reductase kinase kinase and [gamma-(32)P]ATP plus Mg(2+) revealed that the (32)P radioactivity and reductase kinase enzymic activity were located in a single electrophoretic position. Dephosphorylation of (32)P-labeled purified reductase kinase with phosphoprotein phosphatase was associated with significant loss of radioactivity and enzymic activity in the protein band ascribed to reductase kinase. These results provide evidence that the activity of reductase kinase, like HMG-CoA reductase, is modulated by a reversible phosphorylation-dephosphorylation reaction sequence.

Adenosine Triphosphate↗
PubMed2026

A Novel PTPN2 Isoform Differentially Regulates Immune Response.

Genome-wide association studies implicate the PTPN2 gene locus (18p11.21) in risk for several autoimmune diseases, including inflammatory bowel disease. Through genetic fine mapping, we identified the single-nucleotide polymorphism rs80262450 in the PTPN2 gene as the putative causal variant. Analysis of GTEx tissue samples and genetically engineered myeloid cell lines carrying risk and nonrisk alleles of rs80262450 demonstrated increased expression of the PTPN2 splice isoform 4 (PTPN2.4), suggesting that the rs80262450 enhances disease susceptibility by favoring production of PTPN2.4. Furthermore, we found that PTPN2.4 contains a nuclear export sequence (NES) that leads to its retention in the cytoplasm. Differential localization of PTPN2.4 isoform results in a distinct protein binding profile revealed by mass-spectrometry analysis, and its overexpression increased TNF-α. PTPN2.4 knockdown reduced pro-inflammatory cytokines in human macrophages. Mutations within the NES motif abolished the unique localization and function of PTPN2.4. Lastly, increased expression of PTPN2.4 was found in Crohn's disease tissues, demonstrating its involvement in the disease. Together, we identified the pathogenic isoform PTPN2.4 as a novel driver of intestinal inflammation and a potential target to attenuate inflammation in IBD.

Humans↗
PubMed1977

On the mechanism of ATP-induced shape changes in human erythrocyte membranes. II. The role of ATP.

In the preceding paper (Sheetz, M. and S.J. Singer. 1977. J Cell Biol. 73:638-646) it was shown that erythrocyte ghosts undergo pronounced shape changes in the presence of mg-ATP. The biochemical effects of the action of ATP are herein examined. The biochemical effects of the action of ATP are herein examined. Phosphorylation by ATP of spectrin component 2 of the erythrocyte membrane is known to occur. We have shown that it is only membrane protein that is significantly phosphorylated under the conditions where the shape changes are produced. The extent of this phosphorylation rises with increasing ATP concentration, reaching nearly 1 mol phosphoryle group per mole of component 2 at 8mM ATP. Most of this phosphorylation appears to occur at a single site on the protein molecule, according to cyanogen bromide peptide cleavage experiments. The degree of phosphorylation of component 2 is apparently also regulated by a membrane-bound protein phosphatase. This activity can be demonstrated in erythrocyte ghosts prepared from intact cells prelabeled with [(32)P]phosphate. In addition to the phosphorylation of component 2, some phosphorylation of lipids, mainly of phosphatidylinositol, is also known to occur. The ghost shape changes are, however, shown to be correlated with the degree of phosphorylation of component 2. In such experiment, the incorporation of exogenous phosphatases into ghosts reversed the shape changes produced by ATP, or by the membrane-intercalating drug chlorpromazine. The results obtained in this and the preceding paper are consistent with the proposal that the erythrocyte membrane possesses kinase and phosphates activities which produce phosphorylation and dephosphorylation of a specific site on spectrin component 2 molecules; the steady-state level of this phosphorylation regulates the structural state of the spectrin complex on the cytoplasmic surface of the membrane, which in turn exerts an important control on the shape of the cell.

Adenosine Triphosphate↗
PubMed1979

Interaction of plasma lipoproteins with erythrocytes. II. Modulation of membrane-associated enzymes.

When incubated with intact erythrocytes, low density lipoproteins (LDL) decrease the phosphate content of erythrocyte spectrin allowing the cells to undergo morphological transformation. The phosphate content of spectrin depends on the balance between the activity of membrane-associated cyclic AMP-independent protein kinases and phosphoprotein phosphates. LDL do not influence the activity of membrane-associated cyclic AMP-independent protein kinases; these lipoproteins activate by 2-fold and greater membrane-associated phosphatases as determined by hydrolysis of p-nitrophenyl phosphate and by phosphate hydrolysis of phosphorylated erythrocyte membrane proteins. We conclude that LDL interact at the exterior surface of the erythrocyte to stimulate dephosphorylation of spectrin. The significance of this conclusion is augmented by the fact that spectrin, the target for LDL-induced dephosphorylation, specifies cell morphology and modulates the distribution of cell-surface receptors. LDL also render erythrocyte acetylcholinesterase less susceptible to inhition by F-. Lipoproteins in the high density class (HDL) do not stimulate dephosphorylation of spectrin, and they are consequently unable to alter erythrocyte morphology. HDL do prevent the LDL-induced activation of membrane phosphatase. The inhibitory capacity of HDL is observed over the range of LDL:HDL (w/w) which exists in the plasma of normolipemic humans.

Acetylcholinesterase↗