• KSBB Journal
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• v.7 no.4
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• pp.302-307
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• 1992

Protein phosphatase 2A was obtained from a cytosolic fraction of bovine brain homogenate. The phosphatase activity using phosphorylated histone Hl as substrate was suppressed in the presence of liposomes composed of dipalmitoylphosphatidylcholine(DPPC) or the mixture of phosphatidylserine and DPPC. The binding of protein phosphatase to liposome was indicated by the facts that the phosphatase activity of the supernatant of protein phosphatase/multilayer vesicle mixture was decreased with increasing amount of liposome, and that [$^{125}I$]-labeled protein phosphatase was coeluted with liposome. However, the affinity of the protein for phospholipid membrane was not so high. On the other hand, okadaic acid and liposome reduced the phosphatase activity synergistically, which means that okadaic acid binds neither to lipid membrane nor to the membrane-associated phosphatase, The inhibitory effect of liposome was, therefore, ascribed to association of the protein phosphatase 2A with the lipid bilayer membrane.

• Journal of Life Science
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• v.21 no.1
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• pp.31-35
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• 2011

Dual-specificity protein phosphatases (DUSPs) constitute a family of protein phosphatase characterized by the ability to dephosphorylate phospho-tyrosyl and phospho-seryl/threonyl residues. Most DUSPs are involved in regulation of cell survival and differentiation. In this study, a human dual-specificity protein phosphatase, DUSP28, was isolated from a human kidney cDNA. The recombinant protein was successfully produed in E.coli and showed sufficient phosphatase activity toward DiFMUP (6,8-difluoro-4-methylumbelliferyl phosphate). Various phosphatase inhibitors and divalent metals were tested for their effects on the DUSP28 phosphatase activity. As a result, $Zn^{2+}$ was found to strongly inhibit DUSP28 phosphatase activity, suggesting DUSP28 is involved in Zn-related signal transduction pathway. Furthermore, the DUSP28 protein preferred phospho-tyrosyl residues to phospho-threonyl residues, implying its physiological roles in the cellular process.

• Molecules and Cells
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• v.28 no.1
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• pp.25-30
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• 2009

${\beta}$-Arrestins turn off G protein-mediated signals and initiate distinct G protein-independent signaling pathways. We previously demonstrated that angiotensin $AT_1$ receptorbound ${\beta}$-arrestin 1 is cleaved after $Phe^{388}$ upon angiotensin II stimulation. The mechanism and signaling pathway of angiotensin II-induced ${\beta}$-arrestin cleavage remain largely unknown. Here, we show that protein Tyr phosphatase activity is involved in the regulation of ${\beta}$-arrestin 1 cleavage. Tagging of green fluorescent protein (GFP) either to the N-terminus or C-terminus of ${\beta}$-arrestin 1 induced conformational changes and the cleavage of ${\beta}$-arrestin 1 without angiotensin $AT_1$ receptor activation. Orthovanadate and molybdate, inhibitors of protein Tyr phosphatase, attenuated the cleavage of C-terminal GFP-tagged ${\beta}$-arrestin 1 in vitro. The inhibitory effects of okadaic acid and pyrophosphate, which are inhibitors of protein Ser/Thr phosphatase, were less than those of protein Tyr phosphatase inhibitors. Cell-permeable pervanadate inhibited angiotensin II-induced cleavage of ${\beta}$-arrestin 1 in COS-1 cells. Our findings suggest that Tyr phosphorylation signaling is involved in the regulation of angiotensin II-induced ${\beta}$-arrestin cleavage.

• Korean Journal of Pharmacognosy
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• v.41 no.3
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• pp.227-231
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• 2010

Protein tyrosine phosphatase 1B (PTP1B) is predicted to be therapeutic target in treatment of type 2 diabetes and obesity. Thus, in order to search for PTP1B inhibitors, we screened the inhibitory activity of PTP1B in the water extracts of 84 medicinal herbs. Among them, the extracts of Pini Folium, Magnoliae Cortex, Artemisiae asiaticae Herba, Schizonepetae Herba, Menthae Herba, Mume Fructus, Cimicifugae Rhizoma, and Amomi Cardamomi Fructus showed relatively significant (58-68%) inhibitory activity against PTP1B. Especially, the methylene chloride fraction of the methanol extract of Menthae Herba (81% inhibition at 30 ${\mu}g$/ml) showed more potent inhibitory activity against PTP1B than others.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.6
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• pp.3669-3676
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• 2013

Faithful transmission of genetic information depends on accurate chromosome segregation as cells exit from mitosis, and errors in chromosomal segregation are catastrophic and may lead to aneuploidy which is the hallmark of cancer. In eukaryotes, an elaborate molecular control system ensures proper orchestration of events at mitotic exit. Phosphorylation of specific tyrosyl residues is a major control mechanism for cellular proliferation and the activities of protein tyrosine kinases and phosphatases must be integrated. Although mitotic kinases are well characterized, phosphatases involved in mitosis remain largely elusive. Here we identify a novel variant of mouse protein tyrosine phosphatase containing domain 1 (Ptpcd1), that we named Ptpcd2. Ptpcd1 is a Cdc14 related centrosomal phosphatase. Our newly identified Ptpcd2 shared a significant homology to yeast Cdc14p (34.1%) and other Cdc14 family of phosphatases. By subcellular fractionation Ptpcd2 was found to be enriched in the cytoplasm and nuclear pellets with catalytic phosphatase activity. By means of immunofluorescence, Ptpcd2 was spatiotemporally regulated in a cell cycle dependent manner with cytoplasmic abundance during mitosis, followed by nuclear localization during interphase. Overexpression of Ptpcd2 induced mitotic exit with decreased levels of some mitotic markers. Moreover, Ptpcd2 failed to colocalize with the centrosomal marker ${\gamma}$-tubulin, suggesting it as a non-centrosomal protein. Taken together, Ptpcd2 phosphatase appears a non-centrosomal variant of Ptpcd1 with probable mitotic functions. The identification of this new phosphatase suggests the existence of an interacting phosphatase network that controls mammalian mitosis and provides new drug targets for anticancer modalities.

• Molecules and Cells
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• v.43 no.12
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• pp.1035-1045
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• 2020

The Drosophila genome contains four low molecular weight-protein tyrosine phosphatase (LMW-PTP) members: Primo-1, Primo-2, CG14297, and CG31469. The lack of intensive biochemical analysis has limited our understanding of these proteins. Primo-1 and CG31469 were previously classified as pseudophosphatases, but CG31469 was also suggested to be a putative protein arginine phosphatase. Herein, we present the crystal structures of CG31469 and Primo-1, which are the first Drosophila LMW-PTP structures. Structural analysis showed that the two proteins adopt the typical LMW-PTP fold and have a canonically arranged P-loop. Intriguingly, while Primo-1 is presumed to be a canonical LMW-PTP, CG31469 is unique as it contains a threonine residue at the fifth position of the P-loop motif instead of highly conserved isoleucine and a characteristically narrow active site pocket, which should facilitate the accommodation of phosphoarginine. Subsequent biochemical analysis revealed that Primo-1 and CG31469 are enzymatically active on phosphotyrosine and phosphoarginine, respectively, refuting their classification as pseudophosphatases. Collectively, we provide structural and biochemical data on two Drosophila proteins: Primo-1, the canonical LMW-PTP protein, and CG31469, the first investigated eukaryotic protein arginine phosphatase. We named CG31469 as DARP, which stands for Drosophila ARginine Phosphatase.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3812-3814
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• 2010

• Molecules and Cells
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• v.42 no.7
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• pp.546-556
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• 2019

Protein phosphatase 4 (PP4) is a crucial protein complex that plays an important role in DNA damage response (DDR), including DNA repair, cell cycle arrest and apoptosis. Despite the significance of PP4, the mechanism by which PP4 is regulated remains to be elucidated. Here, we identified a novel PP4 inhibitor, protein phosphatase 4 inhibitory protein (PP4IP) and elucidated its cellular functions. PP4IP-knockout cells were generated using the CRISPR/Cas9 system, and the phosphorylation status of PP4 substrates (H2AX, KAP1, and RPA2) was analyzed. Then we investigated that how PP4IP affects the cellular functions of PP4 by immunoprecipitation, immunofluorescence, and DNA double-strand break (DSB) repair assays. PP4IP interacts with PP4 complex, which is affected by DNA damage and cell cycle progression and decreases the dephosphorylational activity of PP4. Both overexpression and depletion of PP4IP impairs DSB repairs and sensitizes cells to genotoxic stress, suggesting timely inhibition of PP4 to be indispensable for cells in responding to DNA damage. Our results identify a novel inhibitor of PP4 that inhibits PP4-mediated cellular functions and establish the physiological importance of this regulation. In addition, PP4IP might be developed as potential therapeutic reagents for targeting tumors particularly with high level of PP4C expression.

• Journal of Life Science
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• v.27 no.3
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• pp.370-381
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• 2017

Protein dephosphorylation is important for cellular regulation, which is catalyzed by protein phosphatases. Among protein phosphatases, carboxy-terminal domain (CTD) phosphatases are recently emerging and new functional roles of them have been revealed. There are 7 CTD phosphatases in human genome, which are composed of CTD phosphatase 1 (CTDP1), CTD small phosphatase 1 (CTDSP1), CTD small phosphatase 2 (CTDSP2), CTD small phosphatase-like (CTDSPL), CTD small phosphatase-like 2 (CTDSPL2), CTD nuclear envelope phosphatase (CTDNEP1), and ubiquitin-like domain containing CTD phosphatase 1 (UBLCP1). CTDP1 dephosphorylates the second phosphor-serine of CTD of RNA polymerase II (RNAPII), while CTDSP1, STDSP2, and CTDSPL dephosphorylate the fifth phosphor-serine of CTD of RNAPII. In addition, CTDSP1 dephosphorylates new substrates such as mothers against decapentaplegic homologs (SMADs), cell division cycle-associated protein 3 (CDCA3), Twist1, tumor-suppressor protein promyelocytic leukemia (PML), and c-Myc. CTDP1 is related to RNA polymerase II complex recycling, mitosis regulation and cancer cell growth. CTDSP1, CTDSP2 and CTDSPL are related to transcription factor recruitment, tumor suppressor function and stem cell differentiation. CTDNEP1 dephosphorylates LIPIN1 and is related to neural tube formation and nuclear envelope formation. CTDSPL2 is related to hematopoietic stem cell differentiation. UBLCP1 dephosphorylates 26S proteasome and is related to nuclear proteasome regulation. In conclusion, noble roles of CTD phosphatases are emerging through recent researches and this review is intended to summarize emerging roles of CTD phosphatases.

• Journal of Marine Bioscience and Biotechnology
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• v.2 no.4
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• pp.230-233
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• 2007

Protein tyrosine phosphatase 1B (PTP1B) acts as a negative regulator of insulin signaling, and selective inhibition of PTP1B has served as a potential drug target for the treatment of type 2 diabetes. As part of our searching for PTP1B inhibitors from natural products, the extracts of marine microorganisms were screened for the inhibitory effects on the activity of protein tyrosine phosphatase 1B (PTP1B). Among the tested 304 extracts, 29 extracts exhibited inhibition rate ranging 40.1 - 83.6 % against PTP1B at the concentration level of $30{\mu}g/mL$.