scholarly journals Constitutive secretion of serum albumin requires reversible protein tyrosine phosphorylation events in trans-Golgi

2005 ◽  
Vol 289 (3) ◽  
pp. C748-C756 ◽  
Author(s):  
Rachel J. Webb ◽  
Jacob D. Judah ◽  
Lee-Chiang Lo ◽  
Geraint M. H. Thomas
Keyword(s):  
Serum Albumin ◽  
Tyrosine Phosphorylation ◽  
Tyrosine Kinases ◽  
Kinase Inhibitor ◽  
Tyrosine Phosphatase ◽  
Protein Tyrosine Phosphatases ◽  
Protein Tyrosine Phosphorylation ◽  
Albumin Secretion ◽  
Protein Tyrosine ◽  
Constitutive Secretion

Serum albumin secretion from rat hepatocytes proceeds via the constitutive pathway. Although much is known about the role of protein tyrosine phosphorylation in regulated secretion, nothing is known about its function in the constitutive process. Here we show that albumin secretion is inhibited by the tyrosine kinase inhibitor genistein but relatively insensitive to subtype-selective inhibitors or treatments. Secretion is also blocked in a physiologically identical manner by the tyrosine phosphatase inhibitors pervanadate and bisperoxo(1,10-phenanthroline)-oxovanadate. Inhibition of either the kinase(s) or phosphatase(s) leads to the accumulation of albumin between the trans-Golgi and the plasma membrane, whereas the immediate precursor proalbumin builds up in a proximal compartment. The trans-Golgi marker TGN38 is rapidly dispersed under conditions that inhibit tyrosine phosphatase action, whereas the distribution of the cis-Golgi marker GM130 is insensitive to genistein or pervanadate. By using a specifically reactive biotinylation probe, we detected protein tyrosine phosphatases in highly purified rat liver Golgi membranes. These membranes also contain both endogenous tyrosine kinases and their substrates, indicating that enzymes and substrates for reversible tyrosine phosphorylation are normal membrane-resident components of this trafficking compartment. In the absence of perturbation of actin filaments and microtubules, we conclude that reversible protein tyrosine phosphorylation in the trans-Golgi network is essential for albumin secretion and propose that the constitutive secretion of albumin is in fact a regulated process.

scholarly journals Effects of Src Kinase Inhibition on Expression of Protein Tyrosine Phosphatase 1B after Brain Hypoxia in a Piglet Animal Model

2017 ◽  
Vol 2017 ◽  
pp. 1-7
Author(s):  
Dimitrios Angelis ◽  
Maria Delivoria-Papadopoulos
Keyword(s):  
Posttranslational Modifications ◽  
Tyrosine Kinases ◽  
Kinase Inhibitor ◽  
Tyrosine Phosphatase ◽  
Src Kinase ◽  
Protein Tyrosine Phosphatases ◽  
Kinase Inhibition ◽  
Protein Tyrosine ◽  
Newborn Piglets ◽  
Ptp 1B

Background. Protein tyrosine phosphatases (PTPs) in conjunction with protein tyrosine kinases (PTKs) regulate cellular processes by posttranslational modifications of signal transduction proteins. PTP nonreceptor type 1B (PTP-1B) is an enzyme of the PTP family. We have previously shown that hypoxia induces an increase in activation of a class of nonreceptor PTK, the Src kinases. In the present study, we investigated the changes that occur in the expression of PTP-1B in the cytosolic component of the brain of newborn piglets acutely after hypoxia as well as long term for up to 2 weeks.Methods. Newborn piglets were divided into groups: normoxia, hypoxia, hypoxia followed by 1 day and 15 days in FiO20.21, and hypoxia pretreated with Src kinase inhibitor PP2, prior to hypoxia followed by 1 day and 15 days. Hypoxia was achieved by providing 7% FiO2for 1 hour and PTP-1B expression was measured via immunoblotting.Results. PTP-1B increased posthypoxia by about 30% and persisted for 2 weeks while Src kinase inhibition attenuated the expected PTP-1B-increased expression.Conclusions. Our study suggests that Src kinase mediates a hypoxia-induced increased PTP-1B expression.

scholarly journals Protein tyrosine phosphatase containing SH2 domains: characterization, preferential expression in hematopoietic cells, and localization to human chromosome 12p12-p13.

1992 ◽  
Vol 12 (2) ◽  
pp. 836-846 ◽  
Author(s):  
T L Yi ◽  
J L Cleveland ◽  
J N Ihle
Keyword(s):  
Tyrosine Phosphorylation ◽  
Protein Tyrosine Phosphatase ◽  
Human Gene ◽  
Tyrosine Phosphatase ◽  
Hematopoietic Cells ◽  
Protein Tyrosine Phosphatases ◽  
Hematopoietic Cell ◽  
Protein Tyrosine Phosphorylation ◽  
Tyrosine Phosphatases ◽  
Protein Tyrosine

Protein tyrosine phosphorylation has been implicated in the growth and functional responses of hematopoietic cells. Recently, approaches have been developed to characterize the protein tyrosine phosphatases that may contribute to regulation of protein tyrosine phosphorylation. One novel protein tyrosine phosphatase was expressed predominantly in hematopoietic cells. Hematopoietic cell phosphatase encodes a 68-kDa protein that contains a single phosphatase conserved domain. Unlike other known protein tyrosine phosphatases, hematopoietic cell phosphatase contains two src homology 2 domains. We also cloned the human homolog, which has 95% amino acid sequence identity. Both the murine and human gene products have tyrosine-specific phosphatase activity, and both are expressed predominantly in hematopoietic cells. Importantly, the human gene maps to chromosome 12 region p12-p13. This region is associated with rearrangements in approximately 10% of cases of acute lymphocytic leukemia in children.

scholarly journals Recent advances in PTP1B signaling in metabolism and cancer

2021 ◽  
Author(s):  
Olga Villamar-Cruz ◽  
Marco A. Loza-Mejía ◽  
Luis E. Arias-Romero ◽  
Ignacio Camacho-Arroyo
Keyword(s):  
Signaling Pathways ◽  
Tyrosine Phosphorylation ◽  
Cancer Progression ◽  
Tyrosine Kinases ◽  
Critical Role ◽  
Protein Tyrosine Phosphatases ◽  
Protein Tyrosine Phosphorylation ◽  
Protein Tyrosine ◽  
Promising Therapeutic Target ◽  
Molecular Aspects

Protein tyrosine phosphorylation is one of the major post-translational modifications in eukaryotic cells and represents a critical regulatory mechanism of a wide variety of signaling pathways. Aberrant protein tyrosine phosphorylation has been linked to various diseases, including metabolic disorders and cancer. Few years ago, protein tyrosine phosphatases (PTPs) were considered as tumor suppressors, able to block the signals emanated from receptor tyrosine kinases. However, recent evidence demonstrates that a misregulation of PTPs activity plays a critical role in cancer development and progression. Here, we will focus on PTP1B, an enzyme that has been linked to the development of type 2 diabetes and obesity through the regulation of insulin and leptin signaling, and with a promoting role in the development of different types of cancer through the activation of several pro-survival signaling pathways. In this review, we discuss the molecular aspects that support the crucial role of PTP1B in different cellular processes underlying diabetes, obesity and cancer progression, and its visualization as a promising therapeutic target.

Protein tyrosine phosphatase containing SH2 domains: characterization, preferential expression in hematopoietic cells, and localization to human chromosome 12p12-p13

1992 ◽  
Vol 12 (2) ◽  
pp. 836-846
Author(s):  
T L Yi ◽  
J L Cleveland ◽  
J N Ihle
Keyword(s):  
Tyrosine Phosphorylation ◽  
Protein Tyrosine Phosphatase ◽  
Human Gene ◽  
Tyrosine Phosphatase ◽  
Hematopoietic Cells ◽  
Protein Tyrosine Phosphatases ◽  
Hematopoietic Cell ◽  
Protein Tyrosine Phosphorylation ◽  
Tyrosine Phosphatases ◽  
Protein Tyrosine

Protein tyrosine phosphorylation has been implicated in the growth and functional responses of hematopoietic cells. Recently, approaches have been developed to characterize the protein tyrosine phosphatases that may contribute to regulation of protein tyrosine phosphorylation. One novel protein tyrosine phosphatase was expressed predominantly in hematopoietic cells. Hematopoietic cell phosphatase encodes a 68-kDa protein that contains a single phosphatase conserved domain. Unlike other known protein tyrosine phosphatases, hematopoietic cell phosphatase contains two src homology 2 domains. We also cloned the human homolog, which has 95% amino acid sequence identity. Both the murine and human gene products have tyrosine-specific phosphatase activity, and both are expressed predominantly in hematopoietic cells. Importantly, the human gene maps to chromosome 12 region p12-p13. This region is associated with rearrangements in approximately 10% of cases of acute lymphocytic leukemia in children.

Role of protein tyrosine phosphorylation in acetaldehyde-induced disruption of epithelial tight junctions

2001 ◽  
Vol 280 (6) ◽  
pp. G1280-G1288 ◽  
Author(s):  
K. J. Atkinson ◽  
R. K. Rao
Keyword(s):  
Tyrosine Phosphorylation ◽  
Tight Junctions ◽  
Tyrosine Kinases ◽  
Tyrosine Phosphatase ◽  
Cell Monolayer ◽  
Protein Tyrosine Phosphorylation ◽  
Protein Tyrosine ◽  
Molecular Masses ◽  
Ptp 1B

Acetaldehyde-induced cytotoxicity is an important factor in pathogenesis of alcohol-related diseases; however, the mechanism of this toxicity is unknown. We recently showed that acetaldehyde increases epithelial paracellular permeability. We asked whether protein tyrosine phosphorylation via modulation of tyrosine kinases and/or PTPases is a mechanism involved in acetaldehyde-induced disruption of the tight junctions in the Caco-2 cell monolayer. Immunofluorescence localization of occludin and ZO-1 showed disruption of the tight junctions in acetaldehyde-treated cell monolayer. Administration of genistein prevented acetaldehyde-induced permeability. Acetaldehyde increased tyrosine phosphorylation of three clusters of proteins with molecular masses of 30–50, 60–90, and 110–150 kDa; three of these proteins were ZO-1, E-cadherin, and β-catenin. Acetaldehyde reduced PTPase activity in plasma membrane and soluble fractions, whereas tyrosine kinase activity remained unaffected. Treatment with acetaldehyde resulted in a 97% loss of protein tyrosine phosphatase (PTP)1B activity and a partial reduction of PTP1C and PTP1D activities. These results strongly suggest that acetaldehyde inhibits PTPases to increase protein tyrosine phosphorylation, which may result in disruption of the tight junctions.

scholarly journals Development of a Robust High-Throughput Screening Platform for Inhibitors of the Striatal-Enriched Tyrosine Phosphatase (STEP)

2021 ◽  
Vol 22 (9) ◽  
pp. 4417
Author(s):  
Lester J Lambert ◽  
Stefan Grotegut ◽  
Maria Celeridad ◽  
Palak Gosalia ◽  
Laurent JS De Backer ◽  
...  
Keyword(s):  
Drug Discovery ◽  
High Throughput ◽  
Tyrosine Kinases ◽  
High Throughput Screening ◽  
Kinase Inhibitors ◽  
Tyrosine Phosphatase ◽  
Protein Tyrosine Phosphatases ◽  
Synaptic Function ◽  
Label Free ◽  
Protein Tyrosine

Many human diseases are the result of abnormal expression or activation of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). Not surprisingly, more than 30 tyrosine kinase inhibitors (TKIs) are currently in clinical use and provide unique treatment options for many patients. PTPs on the other hand have long been regarded as “undruggable” and only recently have gained increased attention in drug discovery. Striatal-enriched tyrosine phosphatase (STEP) is a neuron-specific PTP that is overactive in Alzheimer’s disease (AD) and other neurodegenerative and neuropsychiatric disorders, including Parkinson’s disease, schizophrenia, and fragile X syndrome. An emergent model suggests that the increase in STEP activity interferes with synaptic function and contributes to the characteristic cognitive and behavioral deficits present in these diseases. Prior efforts to generate STEP inhibitors with properties that warrant clinical development have largely failed. To identify novel STEP inhibitor scaffolds, we developed a biophysical, label-free high-throughput screening (HTS) platform based on the protein thermal shift (PTS) technology. In contrast to conventional HTS using STEP enzymatic assays, we found the PTS platform highly robust and capable of identifying true hits with confirmed STEP inhibitory activity and selectivity. This new platform promises to greatly advance STEP drug discovery and should be applicable to other PTP targets.

Protein tyrosine phosphatase-α complexes with the IGF-I receptor and undergoes IGF-I-stimulated tyrosine phosphorylation that mediates cell migration

2009 ◽  
Vol 297 (1) ◽  
pp. C133-C139 ◽  
Author(s):  
Shirley C. Chen ◽  
Ranvikram S. Khanna ◽  
Darrell C. Bessette ◽  
Lionel A. Samayawardhena ◽  
Catherine J. Pallen
Keyword(s):  
Cell Migration ◽  
Tyrosine Phosphorylation ◽  
Protein Tyrosine Phosphatase ◽  
Tyrosine Kinases ◽  
Tyrosine Phosphatase ◽  
Phosphorylation Site ◽  
Protein Tyrosine ◽  
Fibroblast Migration ◽  
Igf I ◽  
In Cells

Protein tyrosine phosphatase-α (PTPα) is a widely expressed receptor-type phosphatase that functions in multiple signaling systems. The actions of PTPα can be regulated by its phosphorylation on serine and tyrosine residues, although little is known about the conditions that promote PTPα phosphorylation. In this study, we tested the ability of several extracellular factors to stimulate PTPα tyrosine phosphorylation. The growth factors IGF-I and acidic FGF induced the highest increase in PTPα phosphorylation at tyrosine 789, followed by PMA and lysophosphatidic acid, while EGF had little effect. Further investigation of IGF-I-induced PTPα tyrosine phosphorylation demonstrated that this occurs through a novel Src family kinase-independent mechanism that does not require focal adhesion kinase, phosphatidylinositol 3-kinase, or MEK. We also show that PTPα physically interacts with the IGF-I receptor. In contrast to IGF-I-induced PTPα phosphorylation, this association does not require IGF-I. The interaction of PTPα and the IGF-I receptor is independent of PTPα catalytic activity, and expression of exogenous PTPα does not promote IGF-I receptor tyrosine dephosphorylation, indicating that PTPα does not act as an IGF-I receptor phosphatase. However, PTPα mediates IGF-I signaling, because IGF-I-stimulated fibroblast migration was reduced by ∼50% in cells lacking PTPα or in cells with mutant PTPα lacking the tyrosine 789 phosphorylation site. Our results suggest that PTPα tyrosine phosphorylation can occur in response to diverse stimuli and can be mediated by various tyrosine kinases. In the case of IGF-I, we propose that IGF-I-induced tyrosine 789 phosphorylation of PTPα, possibly catalyzed by the PTPα-associated IGF-I receptor tyrosine kinase, is required for efficient cell migration in response to this growth factor.

Streptococcus sanguis-induced platelet activation involves two waves of tyrosine phosphorylation mediated by FcγRIIA and αIIbβ3

2005 ◽  
Vol 93 (05) ◽  
pp. 932-939 ◽  
Author(s):  
Caroline Pampolina ◽  
Archibald McNicol
Keyword(s):  
Signal Transduction ◽  
Platelet Aggregation ◽  
Tyrosine Phosphorylation ◽  
Platelet Activation ◽  
Tyrosine Phosphatase ◽  
Protein Tyrosine Phosphatases ◽  
Lag Phase ◽  
Dependent Manner ◽  
Protein Tyrosine ◽  
Streptococcus Sanguis

SummaryThe low-affinity IgG receptor, FcγRIIA, has been implicated in Streptococcus sanguis-induced platelet aggregation. Therefore, it is likely that signal transduction is at least partly mediated by FcγRIIA activation and a tyrosine kinase-dependent pathway. In this study the signal transduction mechanisms associated with platelet activation in response to the oral bacterium, S. sanguis were characterised. In the presence of IgG, S. sanguis strain 2017–78 caused the tyrosine phosphorylation of FcγRIIA 30s following stimulation, which led to the phosphorylation of Syk, LAT, and PLCγ2. These early events were dependent on Src family kinases but independent of either TxA2 or the engagement of the αIIbβ3 integrin. During the lag phase prior to platelet aggregation, FcγRIIA, Syk, LAT, and PLCγ2 were each dephosphorylated, but were re-phosphorylated as aggregation occurred. Platelet stimulation by 2017–78 also induced the tyrosine phosphorylation of PECAM-1, an ITIM-containing receptor that recruits protein tyrosine phosphatases. PECAM-1 co-precipitated with the protein tyrosine phosphatase SHP-1 in the lag phase. SHP-1 was also maximally tyrosine phosphorylated during this phase, suggesting a possible role for SHP-1 in the observed dephosphorylation events. As aggregation occurred, SHP-1 was dephosphorylated, while FcγRIIA, Syk, LAT, and PLCγ2 were rephosphorylated in an RGDS-sensitive, and therefore αIIbβ3-dependent, manner. Additionally, TxA2 release, 5-hydro-xytryptamine secretion and phosphatidic acid formation were all blocked by RGDS. Aspirin also abolished these events, but only partially inhibited αIIbβ3-mediated re-phosphorylation. Therefore, S.sanguis-bound IgG cross links FcγRIIA and initiates a signaling pathway that is down-regulated by PECAM-1-bound SHP-1. Subsequent engagement of αIIbβ3 leads to SHP-1 dephosphorylation permiting a second wave of signaling leading to TxA2 release and consequent platelet aggregation.

scholarly journals Noncatalytic Inhibition of Cyclic Nucleotide–gated Channels by Tyrosine Kinase Induced by Genistein

1999 ◽  
Vol 113 (1) ◽  
pp. 45-56 ◽  
Author(s):  
Elena Molokanova ◽  
Alexei Savchenko ◽  
Richard H. Kramer
Keyword(s):  
Tyrosine Phosphorylation ◽  
Cyclic Nucleotide ◽  
Tyrosine Kinases ◽  
Time Course ◽  
Protein Tyrosine Phosphatases ◽  
Competitive Inhibitor ◽  
Rod Photoreceptor ◽  
Protein Tyrosine ◽  
Atp Binding Site ◽  
Cng Channel

Rod photoreceptor cyclic nucleotide–gated (CNG) channels are modulated by tyrosine phosphorylation. Rod CNG channels expressed in Xenopus oocytes are associated with constitutively active protein tyrosine kinases (PTKs) and protein tyrosine phosphatases that decrease and increase, respectively, the apparent affinity of the channels for cGMP. Here, we examine the effects of genistein, a competitive inhibitor of the ATP binding site, on PTKs. Like other PTK inhibitors (lavendustin A and erbstatin), cytoplasmic application of genistein prevents changes in the cGMP sensitivity that are attributable to tyrosine phosphorylation of the CNG channels. However, unlike these other inhibitors, genistein also slows the activation kinetics and reduces the maximal current through CNG channels at saturating cGMP. These effects occur in the absence of ATP, indicating that they do not involve inhibition of a phosphorylation event, but rather involve an allosteric effect of genistein on CNG channel gating. This could result from direct binding of genistein to the channel; however, the time course of inhibition is surprisingly slow (>30 s), raising the possibility that genistein exerts its effects indirectly. In support of this hypothesis, we find that ligands that selectively bind to PTKs without directly binding to the CNG channel can nonetheless decrease the effect of genistein. Thus, ATP and a nonhydrolyzable ATP derivative competitively inhibit the effect of genistein on the channel. Moreover, erbstatin, an inhibitor of PTKs, can noncompetitively inhibit the effect of genistein. Taken together, these results suggest that in addition to inhibiting tyrosine phosphorylation of the rod CNG channel catalyzed by PTKs, genistein triggers a noncatalytic interaction between the PTK and the channel that allosterically inhibits gating.

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