scholarly journals Increase in receptor-like protein tyrosine phosphatase activity and expression level on density-dependent growth arrest of endothelial cells

1995 ◽  
Vol 311 (1) ◽  
pp. 97-103 ◽  
Author(s):  
F Gaits ◽  
R Y Li ◽  
A Ragab ◽  
J M F Ragab-Thomas ◽  
H Chap
Keyword(s):  
Cell Growth ◽  
Protein Tyrosine Phosphatase ◽  
Tyrosine Phosphatase ◽  
Growth Arrest ◽  
Fold Increase ◽  
Density Dependent ◽  
Protein Tyrosine ◽  
Extracellular Region ◽  
Dependent Growth ◽  
Ptpase Activity

Protein tyrosine phosphatase (PTPase) activity was examined in two cell lines: human umbilical vein endothelial (HUVE) cells, which display contact inhibition of cell growth, and A427 human adenocarcinoma cells, which have lost this ability. HUVE cells harvested at high density displayed a 10-fold increase in membrane-associated PTPase activity. A427 cells exhibited no such phenomenon. Moreover, modification of HUVE cell growth rate by a stimulating agent such as basic fibroblast growth factor or by blocking compounds such as thymidine or suramin resulted in no change in PTPase activity, suggesting that the observed increase in membrane-associated activity at confluency was specific for cell-cell-contact-directed growth arrest. The expression of various PTPase mRNAs was examined in HUVE and A427 cells. Of the receptor-like PTPases tested, two were exclusively expressed in HUVE cells (PTP gamma and HPTP beta). Only HPTP beta, which is structurally similar in its extracellular region to cell-adhesion receptors of the immunoglobulin superfamily, displayed a pattern of expression related to the increase in PTPase activity. Competitive PCR was used to quantify its expression during cell culture. A 12-fold increase in HPTP beta mRNA expression was detected and it parallelled the time course of PTPase activity. This observation strongly implicates receptor-like PTPases in density-dependent growth arrest.

scholarly journals Molecular Determinants of Substrate Recognition in Hematopoietic Protein-tyrosine Phosphatase

2004 ◽  
Vol 279 (50) ◽  
pp. 52150-52159 ◽  
Author(s):  
Zhonghui Huang ◽  
Bo Zhou ◽  
Zhong-Yin Zhang
Keyword(s):  
Substrate Specificity ◽  
Protein Tyrosine Phosphatase ◽  
Cellular Proliferation ◽  
High Efficiency ◽  
Tyrosine Phosphatase ◽  
Substrate Recognition ◽  
Fold Increase ◽  
Phosphoryl Transfer ◽  
Protein Tyrosine ◽  
Hydrolysis Of

The extracellular signal-regulated protein kinase 2 (ERK2) plays a central role in cellular proliferation and differentiation. Full activation of ERK2 requires dual phosphorylation of Thr183and Tyr185in the activation loop. Tyr185dephosphorylation by the hematopoietic protein-tyrosine phosphatase (HePTP) represents an important mechanism for down-regulating ERK2 activity. The bisphosphorylated ERK2 is a highly efficient substrate for HePTP with akcat/Kmof 2.6 × 106m–1s–1. In contrast, thekcatK/mvalues for the HePTP-catalyzed hydrolysis of Tyr(P) peptides are 3 orders of magnitude lower. To gain insight into the molecular basis for HePTP substrate specificity, we analyzed the effects of altering structural features unique to HePTP on the HePTP-catalyzed hydrolysis ofp-nitrophenyl phosphate, Tyr(P) peptides, and its physiological substrate ERK2. Our results suggest that substrate specificity is conferred upon HePTP by both negative and positive selections. To avoid nonspecific tyrosine dephosphorylation, HePTP employs Thr106in the substrate recognition loop as a key negative determinant to restrain its protein-tyrosine phosphatase activity. The extremely high efficiency and fidelity of ERK2 dephosphorylation by HePTP is achieved by a bipartite protein-protein interaction mechanism, in which docking interactions between the kinase interaction motif in HePTP and the common docking site in ERK2 promote the HePTP-catalyzed ERK2 dephosphorylation (∼20-fold increase inkcat/Km) by increasing the local substrate concentration, and second site interactions between the HePTP catalytic site and the ERK2 substrate-binding region enhance catalysis (∼20-fold increase inkcat/Km) by organizing the catalytic residues with respect to Tyr(P)185for optimal phosphoryl transfer.

scholarly journals The Protein Tyrosine Phosphatase H1 PTPH1 Supports Proliferation of Keratinocytes and is a Target of the Human Papillomavirus Type 8 E6 Oncogene

Cells ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 244 ◽  
Author(s):  
Stefanie Taute ◽  
Philipp Böhnke ◽  
Jasmin Sprissler ◽  
Stephanie Buchholz ◽  
Martin Hufbauer ◽  
...  
Keyword(s):  
Skin Cancer ◽  
Cell Growth ◽  
Protein Tyrosine Phosphatase ◽  
Tyrosine Phosphatase ◽  
Organ Transplant ◽  
Growth Factor Receptor ◽  
Human Papillomaviruses ◽  
Keratinocyte Proliferation ◽  
Protein Tyrosine ◽  
Increased Risk

Human papillomaviruses (HPV) replicate their DNA in the suprabasal layer of the infected mucosa or skin. In order to create a suitable environment for vegetative viral DNA replication HPV delay differentiation and sustain keratinocyte proliferation that can lead to hyperplasia. The mechanism underlying cell growth stimulation is not well characterized. Here, we show that the E6 oncoprotein of the βHPV type 8 (HPV8), which infects the cutaneous skin and is associated with skin cancer in Epidermodysplasia verruciformis patients and immunosuppressed organ transplant recipients, binds to the protein tyrosine phosphatase H1 (PTPH1), which resulted in increased protein expression and phosphatase activity of PTPH1. Suppression of PTPH1 in immortalized keratinocytes reduced cell proliferation as well as the level of epidermal growth factor receptor (EGFR). Furthermore, we report that HPV8E6 expressing keratinocytes have increased level of active, GTP-bound Ras. This effect was independent of PTPH1. Therefore, HPV8E6-mediated targeting of PTPH1 might result in higher level of EGFR and enhanced keratinocyte proliferation. The HPV8E6-mediated stimulation of Ras may be an additional step to induce cell growth. Our results provide novel insights into the mechanism how βHPVE6 proteins support proliferation of infected keratinocytes, thus creating an environment with increased risk of development of skin cancer particularly upon UV-induced DNA mutations.

scholarly journals Effects of Overexpression of PTP36, a Putative Protein Tyrosine Phosphatase, on Cell Adhesion, Cell Growth, and Cytoskeletons in HeLa Cells

1999 ◽  
Vol 274 (18) ◽  
pp. 12905-12909 ◽  
Author(s):  
Masato Ogata ◽  
Tsuyoshi Takada ◽  
Yoshiko Mori ◽  
Masatsugu Oh-hora ◽  
Yohzo Uchida ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Cell Growth ◽  
Hela Cells ◽  
Protein Tyrosine Phosphatase ◽  
Tyrosine Phosphatase ◽  
Protein Tyrosine ◽  
Putative Protein

scholarly journals Molecular cloning, characterization, and chromosomal localization of a novel protein-tyrosine phosphatase, HPTP eta

Blood ◽  
1994 ◽  
Vol 84 (12) ◽  
pp. 4186-4194 ◽  
Author(s):  
H Honda ◽  
J Inazawa ◽  
J Nishida ◽  
Y Yazaki ◽  
H Hirai
Keyword(s):  
Protein Tyrosine Phosphatase ◽  
Chromosomal Localization ◽  
Tyrosine Phosphatase ◽  
Protein Tyrosine Phosphatases ◽  
Leukemic Cell ◽  
Coding Region ◽  
Chromosome 11 ◽  
Protein Tyrosine ◽  
Type Iii ◽  
Extracellular Region

Protein-tyrosine phosphatases (PTPases) are considered to play an important role in signal transduction. We previously identified partial sequences of three novel PTPases in a human leukemic cell line. F-36P. We describe here cloning, characterization, and chromosomal localization of one of the newly identified PTPases, termed as HPTP eta (human protein-tyrosine phosphatase eta). The deduced amino acid sequence was composed of an extracellular region homologous to fibronectin type III repeats, a transmembrane region, and a cytoplasmic region containing a single PTPase-like domain. Based on its primary structure, this clone belongs to type-III receptor-type PTPases. The PTPase-like domain showed PTPase activity when expressed in Escherichia coli. Antibody against the extracellular region detected a protein of 220 to 250 kD in human hematopoietic cell lines expressing HPTP eta mRNA. The antibody also recognized a protein of approximately the same molecular weight in COS cells transfected with HPTP eta cDNA, indicating that the antibody specifically recognized HPTP eta gene product and that the cloned cDNA contained full-length coding region. The chromosomal localization determined by fluorescence in situ hybridization showed that the HPTP eta gene was located at chromosome 11p11.2 on the short arm of chromosome 11, which is frequently lost or deleted in human carcinomas.

NO increases protein tyrosine phosphatase activity in smooth muscle cells: relationship to antimitogenesis

1997 ◽  
Vol 272 (3) ◽  
pp. H1342-H1349 ◽  
Author(s):  
G. S. Dhaunsi ◽  
C. Matthews ◽  
K. Kaur ◽  
A. Hassid
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Protein Tyrosine Phosphatase ◽  
Tyrosine Phosphatase ◽  
Muscle Cells ◽  
Aortic Smooth Muscle Cells ◽  
Protein Tyrosine ◽  
Aortic Smooth Muscle ◽  
Cyclic Monophosphate ◽  
Ptpase Activity

We investigated the mechanisms of NO-induced antimitogenesis in primary aortic smooth muscle cells from newborn rats. S-nitroso-N-acetylpenicillamine (SNAP), an NO-releasing agent, decreased basal and growth factor-stimulated DNA synthesis with a threshold effectiveness of 0.3-3 microM. A second NO-releasing agent, 3-morpholinosydnonimine-N-ethylcarbamide, a hydrolysis-resistant cyclic nucleotide, 8-bromo-guanosine 3',5'-cyclic monophosphate (8-BrcGMP), and atrial natriuretic peptides elicited a similar effect, whereas 8-bromo-adenosine 3',5'-cyclic monophosphate (8-BrcAMP) was ineffective, supporting the view that NO and cGMP, but not cAMP, mediated at least some of SNAP's antimitogenic effect. SNAP and 8-BrcGMP decreased the levels of phosphotyrosine, especially in proteins of 70-85 kDa and approximately 215 kDa molecular mass. SNAP decreased protein phosphotyrosine levels with a threshold effectiveness similar to that of its antimitogenic effect. Moreover, SNAP increased protein tyrosine phosphatase (PTPase) activity in cell homogenates, indicating that phosphotyrosine dephosphorylation was likely to be the result of increased PTPase activity. Peroxovanadate, a selective PTPase inhibitor, blocked the antimitogenic effect of 8-BrcGMP, suggesting that loss of protein phosphotyrosine and antimitogenesis were causally linked. These findings describe a potential mechanism for NO-induced antimitogenesis in aortic smooth muscle cells in primary culture.

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