Dual-specificity Protein Tyrosine Phosphatase Research Articles

CDKN3 Overcomes Bladder Cancer Cisplatin Resistance via LDHA-Dependent Glycolysis Reprogramming.

BackgroundAerobic glycolysis plays an important role in bladder cancer (BLCA) progression and chemoresistance. Cyclin-dependent kinase inhibitor-3 (CDKN3), a dual-specificity protein tyrosine phosphatase, has aberrant upregulation in multiple cancer types and is associated with tumorigenesis. However, the role of CDKN3 in BLCA progression and glycolysis has not been elucidated.PurposeIn this study, we investigated the effect and underlying mechanisms of CDKN3 on bladder cancer chemoresistance.ResultsThis study confirmed that CDKN3 was overexpressed in BLCA tissues and promoted proliferation and migration. Additionally, our results showed a CDKN3-dependent mechanism on chemoresistance; chemoresistance cells were transformed into chemosensitivity cells by CDKN3 knockdown. Additionally, we showed that CDKN3 knockdown decreased glycolysis by inhibiting LDHA expression in BLCA chemoresistance cells. The results also proved that LDHA was an important mediator of CDKN3-regulated BLCA resistance. LDHA overexpression reversed glycolysis inhibition and chemosensitivity induced by CDKN3 downregulation.ConclusionThese data collectively identified a vital role of CDKN3 in glycolysis and chemoresistance by regulating LDHA expression in BLCA cells, providing a possible therapeutic strategy for treating BLCA.

AtPFA-DSP5 interacts with MPK3/MPK6 and negatively regulates plant salt responses

ABSTRACT Protein tyrosine phosphatases play essential roles in plant growth and development and in plant responses to biotic or abiotic stresses. We recently demonstrated that an atypical dual-specificity protein tyrosine phosphatase in plants, AtPFA-DSP3 (DSP3), negatively regulates plant salt tolerance. Here, we report that a homolog of DSP3, AtPFA-DSP5 (DSP5), affects the response of plants to high-salt conditions. A loss-of-function mutant of DSP5 showed reduced sensitivity to salt treatment at the seed germination and vegetative stages of development while a gain-of-function mutant of DSP5 showed increased sensitivity to salt stress. The salt responses of dsp3dsp5 double-mutant plants were similar to those of dsp3 and dsp5 single-mutant plants. Gel overlay and firefly luciferase complementation assays showed that DSP5 interacts with MPK3 and MPK6 in vitro and in vivo. These results indicate that DSP5 is a novel negative regulator of salt responses in Arabidopsis that interacts directly with MPK3 and MPK6.

AtPFA-DSP3, an atypical dual-specificity protein tyrosine phosphatase, affects salt stress response by modulating MPK3 and MPK6 activity.

Protein phosphorylation, especially serine/threonine and tyrosine phosphorylation, plays significant roles in signalling during plant growth and development as well as plant responses to biotic or abiotic stresses. Dual-specificity protein tyrosine phosphatases dephosphorylate components of these signalling pathways. Here, we report that an atypical dual-specificity protein tyrosine phosphatase, AtPFA-DSP3 (DSP3), negatively affects the response of plants to high-salt conditions. A DSP3 loss-of-function mutant showed reduced sensitivity to salt treatment. DSP3 was primarily localized in nuclei and was degraded during salt treatment. Compared to wild type, the level of ROS was lower in the dsp3 mutant and higher in plants ectopically expressing DSP3, indicating that higher DSP3 level was associated with increased ROS production. DSP3 interacted with and dephosphorylated MPK3 and MPK6. Genetic analyses of a dsp3mpk3 double mutant revealed that DSP3's effect on salt stress depends on MPK3. Moreover, the phosphatase activity of DSP3 was required for its role in salt signalling. These results indicate that DSP3 is a negative regulator of salt responses in Arabidopsis by directly modulating the accumulation of phosphorylated MPK3 and MPK6.

When transcripts matter: delineating between non-syndromic hearing loss DFNB32 and hearing impairment infertile male syndrome (HIIMS)

Mutations in the CDC14A (Cell Division-Cycle 14A) gene, which encodes a conserved dual-specificity protein tyrosine phosphatase, have been identified as a cause of autosomal recessive non-syndromic hearing loss (DFNB32) and hearing impairment infertility male syndrome (HIIMS). We used next-generation sequencing to screen six deaf probands from six families segregating sensorineural moderate-to-profound hearing loss. Data analysis and variant prioritization were completed using a custom bioinformatics pipeline. We identified three homozygous loss of function variants (p.Arg345Ter, p.Arg376Ter, and p.Ala451Thrfs*43) in the CDC14A gene, segregating with deafness in each family. Of the six families, four segregated the p.Arg376Ter mutation, one family segregated the p.Arg345Ter mutation and one family segregated a novel frameshift (p.Ala451Thrfs*43) mutation. In-depth phenotyping of affected individuals ruled out secondary syndromic findings. This study implicates the p.Arg376Ter mutation might be as a founder mutation in the Iranian population. It also provides the first semen analysis for deaf males carrying mutations in exon 11 of CDC14A and reveals a genotype-phenotype correlation that delineates between DFNB32 and HIIMS. The clinical results from affected males suggest the NM_033313.2 transcript alone is sufficient for proper male fertility, but not for proper auditory function. We conclude that DFNB32 is a distinct phenotypic entity in males.

Tapping the therapeutic potential of protein tyrosine phosphatase 4A with small molecule inhibitors.

Protein tyrosine phosphatases (PTPs) are emerging new targets for drug discovery. PTPs and protein tyrosine kinases (PTKs) maintain cellular homeostasis through opposing roles: tyrosine O-dephosphorylation and -phosphorylation, respectively. An imbalance in the phosphorylation equilibrium results in aberrant protein signaling and pathophysiological conditions. PTPs have historically been considered 'undruggable', in part due to a lack of evidence defining their relationship to disease causality and a focus on purely competitive inhibitors. However, a better understanding of protein-protein interfaces and shallow active sites has recently renewed interest in the pursuit of allosteric and orthosteric modulators of targets outside the major druggable protein families. While their biological mechanism of action still remains to be clarified, PTP4A1-3 (also referred to as PRL1-3) are validated oncology targets and play an important role in cell proliferation, metastasis, and tumor angiogenesis. In this Digest, recent syntheses and structure-activity relationships (SAR) of small molecule inhibitors (SMIs) of PTP4A1-3 are summarized, and enzyme docking studies of the most potent chemotype are highlighted. In particular, the thienopyridone scaffold has emerged as a potent lead structure to interrogate the function and druggability of this dual-specificity PTP.

Abstract 190: Mechanism of CDKN3 overexpression in cancer

Abstract The cyclin-dependent kinase inhibitor 3 (CDKN3) is a dual specificity protein tyrosine phosphatase (PTP) known to dephosphorylate CDK1/2 on the activating Thr-161/Thr-160. Paradoxically, CDKN3 mRNA is often overexpressed in human cancer. It was reported that CDKN3 overexpression may be associated with splicing variants or mutations that produce dominant-negative CDKN3. We found that CDKN3 is overexpressed in non-small cell lung cancer (NSCLC) and that CDKN3 overexpression is prognostic of poor overall survival in three cohorts of lung adenocarcinoma. We next analyzed CDKN3 transcripts in a panel of 24 cell lines and lung adenocarcinoma tissues and also examined CDKN3 mutations in the Cancer Genome Atlas (TCGA) and the Moffitt Cancer Center's Total Cancer Care® (TCC) projects. Two CDKN3 transcripts were detected in all samples. These CDKN3 transcripts represent the full length CDKN3 mRNA and a normal transcript lacking exon 2, which encodes an out of frame 23-amino acid peptide with little homology to CDKN3. CDKN3 mutations were very rare and no disruptive mutation was found. Significantly, in synchronized cell cultures, CDKN3 mRNA and protein were elevated during the mitosis phase of cell cycle. Furthermore, CDKN3 expression had the highest correlation with mitotic-associated genes in lung adenocarcinoma tissues. Knocking down of CDKN3 prolonged the mitotic phase of cell cycle. Thus, CDKN3 overexpression in lung adenocarcinoma is not attributed to alternative splicing or mutation but is due to increased mitotic activity. Our data also suggest that CDKN3 is important for mitotic exit. Citation Format: Chao Fan, Lu Chen, Qingling Huang, Tao Shen, Eric A. Welsh, Jamie K. Teer, W Douglas Cress, Jie Wu. Mechanism of CDKN3 overexpression in cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 190.

The Extended Family of Protein Tyrosine Phosphatases.

In higher eukaryotes, the Tyr phosphorylation status of cellular proteins results from the coordinated action of Protein Tyrosine Kinases (PTKs) and Protein Tyrosine Phosphatases (PTPs). PTPs have emerged as highly regulated enzymes with diverse substrate specificity, and proteins with Tyr-dephosphorylation or Tyr-dephosphorylation-like properties can be clustered as the PTPome. This includes proteins from the PTP superfamily, which display a Cys-based catalytic mechanism, as well as enzymes from other gene families (Asp-based phosphatases, His-based phosphatases) that have converged in protein Tyr-dephosphorylation-related functions by using non-Cys-based catalytic mechanisms. Within the Cys-based members of the PTPome, classical PTPs dephosphorylate specific phosphoTyr (pTyr) residues from protein substrates, whereas VH1-like dual-specificity PTPs dephosphorylate pTyr, pSer, and pThr residues, as well as nonproteinaceous substrates, including phosphoinositides and phosphorylated carbohydrates. In addition, several PTPs have impaired catalytic activity as a result of amino acid substitutions at their active sites, but retain regulatory functions related with pTyr signaling. As a result of their relevant biological activity, many PTPs are linked to human disease, including cancer, neurodevelopmental, and metabolic diseases, making these proteins important drug targets and molecular markers in the clinic. Here, a brief overview on the biochemistry and physiology of the different groups of proteins that belong to the mammalian PTPome is presented.

The mitogen-activated protein kinase phosphatase PHS1 regulates flowering in Arabidopsis thaliana.

Arabidopsis PHS1, initially known as an actor of cytoskeleton organization, is a positive regulator of flowering in the photoperiodic and autonomous pathways by modulating both CO and FLC mRNA levels. Protein phosphorylation and dephosphorylation is a major type of post-translational modification, controlling many biological processes. In Arabidopsis thaliana, five genes encoding MAPK phosphatases (MKP)-like proteins have been identified. Among them, PROPYZAMIDE HYPERSENSITIVE 1 (PHS1) encoding a dual-specificity protein tyrosine phosphatase (DsPTP) has been shown to be involved in microtubule organization, germination and ABA-regulated stomatal opening. Here, we demonstrate that PHS1 also regulates flowering under long-day and short-day conditions. Using physiological, genetic and molecular approaches, we have shown that the late flowering phenotype of the knock-out phs1-5 mutant is linked to a higher expression of FLOWERING LOCUS C (FLC). In contrast, a decline of both CONSTANS (CO) and FLOWERING LOCUS T (FT) expression is observed in the knock-out phs1-5 mutant, especially at the end of the light period under long-day conditions when the induction of flowering occurs. We show that this partial loss of sensitivity to photoperiodic induction is independent of FLC. Our results thus indicate that PHS1 plays a dual role in flowering, in the photoperiodic and autonomous pathways, by modulating both CO and FLC mRNA levels. Our work reveals a novel actor in the complex network of the flowering regulation.

Characterization of a protein tyrosine phosphatase as a host factor promoting baculovirus replication in silkworm, Bombyx mori

The relevance of protein tyrosine phosphatase (PTP) to host–pathogen interaction is highlighted in mammalian studies, whereas less is known in insects. Here we presented the categorization of the PTP complement of silkworm and characterized their homologous relationship with human and fruit fly PTPs. Among the 36 PTP genes, ptp-h, which was proposed to be the origin of baculovirus ptp belongs to atypical VH1-like dual-specific PTP subset and encodes a catalytic active protein. The maximum expression level of Bmptp-h was at 5th instar and in fat body. Bombyx mori nucleopolyhedrovirus (BmNPV) infection potently induced its expression in silkworm larvae and in BmE cells. Knock-down of Bmptp-h by RNA interference significantly inhibited viral replication, and over-expression enhanced viral replication as determined by viral DNA abundance and BmNPV-GFP positive cells. These results suggest that BmPTP-h might be one of the host factors that is beneficial to baculovirus infection by promoting viral replication.

Redox Modulation of PTEN Phosphatase Activity by Hydrogen Peroxide and Bisperoxidovanadium Complexes.

PTEN is a dual-specificity protein tyrosine phosphatase. As one of the central tumor suppressors, a thorough regulation of its activity is essential for proper cellular homeostasis. The precise implications of PTEN inhibition by reactive oxygen species (e.g. H2O2) and the subsequent structural consequences remain elusive. To study the effects of PTEN inhibition, bisperoxidovanadium (bpV) complexes serve as important tools with the potential for the treatment of nerve injury or cardiac ischemia. However, their mode of action is unknown, hampering further optimization and preventing therapeutic applications. Based on protein crystallography, mass spectrometry, and NMR spectroscopy, we elucidate the molecular basis of PTEN inhibition by H2O2 and bpV complexes. We show that both molecules inhibit PTEN via oxidative mechanisms resulting in the formation of the same intramolecular disulfide, therefore enabling the reactivation of PTEN under reductive conditions.

Expression, Purification and Crystallization of the Xanthmonal Avirulence Protein, AvrBs1.1, and its Target in Capsicum annuum, the Transcription Factor WRKY‐1

Brown spots and leaf loss of Capsicum annum, a pepper found in the Americas, are caused by prolonged activation of the plant's defense mechanisms to bacterial infection resulting in a phenomenon called the hypersensitive response. In the hypersensitive response, the plant “walls off” the infected tissue with lignin and then a variety of chemical processes occur within the lignified zone which results in the death of both bacterial and plant cells. Certain species‐specific bacterial pathogens inject effector proteins with different activities into the cytosol of the host to prevent activation of the plant's defense mechanisms. Our work focuses on the effector protein AvrBs1.1, a dual specificity protein tyrosine phosphatase produced by Xanthamonas euvesicatoria. Recent work has identified the transcription factor WRKY‐1 as a possible target for AvrBs1.1. We hypothesize that AvrBs1.1 dephosphorylates WRKY‐1 in the cytosol, thereby preventing it from entering the nucleus and activating the genes of the plant's defense response. In order to understand the molecular basis of the function of AvrBs1.1, we need to determine the x‐ray crystallographic structure of AvrBs1.1 and the AvrBs1.1/WRKY‐1 complex. We crystallized AvrBs1.1 in 2.0M (NH4)SO4, 10% PEG 400, 50mM HEPES pH 7.0, and 50mM ZnSO4. Using this condition as a base, we employed a small molecule additive screen to enhance crystal growth. Four different organic alcohols (MPD, tert‐butanol, PEG 400, and hexanediol) were found to induce the growth of single crystals of AvrBs1.1. In the future, we will screen the AvrBs1.1 crystals for x‐ray diffraction and optimize the expression of WRKY‐1 and attempt to crystallize the AvrBs1.1/WRKY‐1 complex.

Expression, Purification and Crystallization of the Xanthomonas euvesicatoria Dual Specificity Protein Tyrosine Phosphatase, AvrBs1.1

Phytopathogenic xanthomonads possess a type III secretion system that allows delivery of proteins, which serve to disrupt normal cellular function in the host. Avirulence proteins (Avr) are type III effector proteins that are recognized by specific R gene products in resistant hosts. A novel Avr protein, AvrBs1.1, from Xanthomonas euvesicatoria was recently found to elicit a delayed hypersensitive response on Capsicum annuum leaves. Amino acid sequence analysis of AvrBs1.1 has revealed the presence of a Dual‐Specificity Protein Tyrosine Phosphatase domain. Screening for novel resistance genes has identified a single binding partner of AvrBs1.1, the R gene product Bs7. Our laboratory has constructed homology models of AvrBs1.1 which have provided some insight into potential differences in activation of Bs7 in C. annuum, a better understanding of the activation mechanism will be gained by x‐ray crystallographic studies of the protein complexes. We have begun purifying recombinant AvrBs1.1 in quantities suitable for crystallization trials. The coding sequence of X. euvesicatoria AvrBs1.1 was cloned into pET21A, which was used to transform E. coli BL21 (DE3) cultures. The recombinant AvrBs1.1 was purified by a combination of metal chelating affinity and gel filtration chromatographic methods. Aliquots of pure protein were used to identify conditions suitable for growth of diffraction quality crystals.

A selective Seoul-Fluor-based bioprobe, SfBP, for vaccinia H1-related phosphatase—a dual-specific protein tyrosine phosphatase

We report a Seoul-Fluor-based bioprobe, SfBP, for selective monitoring of protein tyrosine phosphatases (PTPs). A rational design based on the structures at the active site of dual-specific PTPs can enable SfBP to selectively monitor the activity of these PTPs with a 93-fold change in brightness. Moreover, screening results of SfBP against 30 classical PTPs and 35 dual-specific PTPs show that it is selective toward vaccinia H1-related (VHR) phosphatase, a dual-specific PTP (DUSP-3).

Structure-based virtual screening approach to the discovery of novel PTPMT1 phosphatase inhibitors

Dual-specificity protein tyrosine phosphatase localized to mitochondrion 1 (PTPMT1) has recently proved to be a promising therapeutic target for the treatment of type II diabetes. Herein we report the first example for a successful application of the structure-based virtual screening to identify the novel inhibitors of human PTPMT1. These inhibitors were computationally screened for having desirable physicochemical properties as a drug candidate and reveal a high potency with IC(50) values ranging from 0.7 to 17.3μM. Therefore, they deserve consideration for further development by structure-activity relationship studies to optimize the antidiabetic activities. Structural features relevant to the stabilization of the newly identified inhibitors in the active site of PTPMT1 are addressed in detail.

Recent Advances in Protein Tyrosine Phosphatase Detection Using Chemical Probes

Protein tyrosine phosphatases (PTPs) are key regulatory enzymes in signal transduction pathways and their aberrancy has been implicated in various diseases such as cancers, metabolic syndrome, and autoimmune disorders. In spite of its great importance, determination of the functional significance of PTPs remains a major challenge, and efficient methodologies are needed to specifically delineate PTP functions. Besides the strategy to use potent and selective PTP inhibitors to study the physiological roles of the enzymes, measurement of PTP activities using specific PTP substrates or activity-based probes (ABPs) has been reported. This review focused on the recent development of small molecular probes to detect PTP activities, consisting of five sub-categories: 1. Conventional fluorescent substrates; 2. Ratiometric fluorescent PTP substrates; 3. Fluorescence substrates with selectivity to a single PTP or a class of PTPs; 4. ABPs specific for PTPs; and 5. A real-time imaging of PTP-substrate complex using a small molecule PTP probe which, offers a measurement of a real-time activity of a certain PTP in cells.

PRL-2 increases Epo and IL-3 responses in hematopoietic cells

Dual specificity protein tyrosine phosphatase PRL-2 is overexpressed in pediatric acute myeloid leukemia (AML) and is located at human chromosome 1p35, a region often rearranged or amplified in malignant lymphoma and B-cell chronic lymphocytic leukemia (B-CLL). Little is known of the significance of PRL-2 expression in hematopoietic malignancies. Herein we demonstrated that ectopic expression of PRL-2 in murine pre-B-cell line Baf3ER and mouse bone marrow cells induced key features associated with malignant progression and metastasis. PRL-2-transfected Baf3ER cells had augmented growth responses to hematopoietic growth factors Epo or IL-3 with shortened cell cycle, reduced requirement (5×) for Epo in cell survival, increased cell migration (3×), reduced cell adhesion (5×), and conversion to an immature cell morphology in association with increased expression (3×) of stem cell marker Bmi-1. When transduced into mouse bone marrow cells, PRL-2 increased Epo-induced colony formation (4×) and gave rise to larger colonies. These observations provide evidences implicating PRL-2 as a pathogenic molecule in hematopoietic malignancies and suggest its potential as a novel therapeutic target.

Pharmacological Targeting of the Mitochondrial Phosphatase PTPMT1

The dual-specificity protein tyrosine phosphatases (PTPs) play integral roles in the regulation of cell signaling. There is a need for new tools to study these phosphatases, and the identification of inhibitors potentially affords not only new means for their study, but also possible therapeutics for the treatment of diseases caused by their dysregulation. However, the identification of selective inhibitors of the protein phosphatases has proven somewhat difficult. PTP localized to mitochondrion 1 (PTPMT1) is a recently discovered dual-specificity phosphatase that has been implicated in the regulation of insulin secretion. Screening of a commercially available small-molecule library yielded alexidine dihydrochloride, a dibiguanide compound, as an effective and selective inhibitor of PTPMT1 with an in vitro concentration that inhibits response by 50% of 1.08 microM. A related dibiguanide analog, chlorhexidine dihydrochloride, also significantly inhibited PTPMT1, albeit with lower potency, while a monobiguanide analog showed very weak inhibition. Treatment of isolated rat pancreatic islets with alexidine dihydrochloride resulted in a dose-dependent increase in insulin secretion, whereas treatment of a pancreatic beta-cell line with the drug affected the phosphorylation of mitochondrial proteins in a manner similar to genetic inhibition of PTPMT1. Furthermore, knockdown of PTPMT1 in rat islets rendered them insensitive to alexidine dihydrochloride treatment, providing evidence for mechanism-based activity of the inhibitor. Taken together, these studies establish alexidine dihydrochloride as an effective inhibitor of PTPMT1, both in vitro and in cells, and support the notion that PTPMT1 could serve as a pharmacological target in the treatment of type II diabetes.

Protein tyrosine phosphatases in glioma biology

Gliomas are a diverse group of brain tumors of glial origin. Most are characterized by diffuse infiltrative growth in the surrounding brain. In combination with their refractive nature to chemotherapy this makes it almost impossible to cure patients using combinations of conventional therapeutic strategies. The drastically increased knowledge about the molecular underpinnings of gliomas during the last decade has elicited high expectations for a more rational and effective therapy for these tumors. Most studies on the molecular pathways involved in glioma biology thus far had a strong focus on growth factor receptor protein tyrosine kinase (PTK) and phosphatidylinositol phosphatase signaling pathways. Except for the tumor suppressor PTEN, much less attention has been paid to the PTK counterparts, the protein tyrosine phosphatase (PTP) superfamily, in gliomas. PTPs are instrumental in the reversible phosphorylation of tyrosine residues and have emerged as important regulators of signaling pathways that are linked to various developmental and disease-related processes. Here, we provide an overview of the current knowledge on PTP involvement in gliomagenesis. So far, the data point to the potential implication of receptor-type (RPTPδ, DEP1, RPTPμ, RPTPζ) and intracellular (PTP1B, TCPTP, SHP2, PTPN13) classical PTPs, dual-specific PTPs (MKP-1, VHP, PRL-3, KAP, PTEN) and the CDC25B and CDC25C PTPs in glioma biology. Like PTKs, these PTPs may represent promising targets for the development of novel diagnostic and therapeutic strategies in the treatment of high-grade gliomas.

Setaria cervidual specific phosphatase: characterization and its effect on eosinophil degranulation

Setaria cervi, a bovine filarial parasite contains significant acid phosphatase (AcP) activity in its various life stages. Two forms of AcP were separated from somatic extract of adult female parasite using cation exchange, gel filtration and concavalin affinity chromatography. One form having a molecular mass of 79 kDa was characterized as dual specific protein tyrosine phosphatase (ScDSP) based on substrate specificity and inhibition studies. With various substrates tested, it showed significant activity in the order of phospho-L-tyrosine>pNPP>ADP>phospho-L-serine. Inhibition by orthovanadate, fluoride, molybdate, and zinc ions further confirms protein tyrosine phosphatase nature of the enzyme. Km and Vmax determined with various substrates were found to be 16.66 mM, 25.0 microM/ml/min with pNPP; 20.0 mM, 40.0 microM/ml/min with phospho-L-tyrosine and 27.0 mM, 25.0 microM/ml/min with phospho-L-serine. KI with pNPP and sodium orthovanadate (IC50 33.0 microM) was calculated to be 50.0 mM. Inhibition with pHMB, silver nitrate, DEPC and EDAC suggested the presence of cysteine, histidine and carboxylate residues at its active site. Cross-reactivity with W. bancrofti-infected sera was demonstrated by Western blotting. ScDSP showed elevated levels of IgE in chronic filarial sera using ELISA. Under in vitro conditions, ScDSP resulted in increased effector function of human eosinophils when stimulated by IgG, which showed a further decrease with increasing enzyme concentration. Results presented here suggest that S. cervi DSP should be further studied to determine its role in pathogenesis and the persistence of filarial parasite.

INTERACTIONS BETWEEN HUMAN SLINGSHOT PHOSPHATASE 2 AND PHOSPHO-COFILIN: A MOLECULAR DYNAMICS STUDY

Human slingshot phosphatase 2 (SSH2) is one of the dual specificity protein tyrosine phosphatases, which can activate cofilin substrate by binding its phosphorylation state. Because the interaction model of SSH2 and phospho-cofilin (P-cofilin) was unknown, we obtained the complex through macromolecular docking method. The molecular dynamics studies were used to investigate the complex dynamics in an aqueous solution. To understand the binding specificity, the free energy was calculated with the molecular mechanics Poisson–Boltzmann surface area (MM/PBSA) approach and the interaction mode in active site was analyzed. The results indicated that the interaction of the P-loop of SSH2 with phosphoserine of human P-cofilin was stabilized by molecular mechanics energy and nonpolar solvation energy components, while polar solvation energy and the entropic contributions were unfavorable for the combination of the two proteins. In addition, the electrostatic contributions were negative for the formation of the complex on the whole, but seen from the active local, the Coulomb interaction between the phosphoserine and the P-loop residues could play an important role in determining substrate specificity.