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1

Participation of 125 kDa tyrosine-phosphorylated protein in phagocytosis of Acanthamoeba cells

100%

Krawczynska W., Sobota A.

Folia Histochemica et Cytobiologica. Supplement

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1996

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tom 34

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nr 1

2

Differential regulation of signalling pathways for insulin and insulin-like growth factor I

100%

Lopaczynski W.

Acta Biochimica Polonica

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1999

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tom 46

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nr 1

The insulin receptor (IR) and the insulin-like growth factor receptor I (IGF-IR) have different functions in cell growth, apoptosis, differentation, and transformation. Although some of these differences may be explained by the relative level of receptor expression and receptor structure (a and b subunits), they may also be attributed to differences in intracellular signals generated by insulin and IGF-I. The presence of hybrid receptors (IR ab subunits and IGF-IR ab subunits) making up the heterotetramers has added a new dimension to our understanding of the functional roles of these receptors. However, to date the results of efforts to understand the differences between these two closely related receptors have indicated mostly similarities. For example, both receptors utilize IRS-1/IRS-2 and Shc as immediate downstream adaptors, leading to activation of the Ras, Raf, ERK kinases and PI-3 kinase pathways. We have used the yeast two hybrid system to identify proteins which bind to the activated IGF-IR but not to the IR. The cytoplasmic domain of the IGF-IR was used to screen a human fetal brain library and two isoforms of the 14-3-3 family were identified. 14-3-3 proteins are a highly conserved family of proteins which have recently been shown to interact with other components of the mitogenic and apoptotic signaling pathways, including Raf, BAD, Bcr/Bcr-Abl, middle-T antigen, Ksr, PKC, PI-3 kinase, ASK1 kinase, and cdc25C phosphatase. We also identified human Grb10, an adaptor protein with SH2 domain associated with the IGF-IR b subunit. Smith's laboratory showed that Grb10 preferentially binds to the IR in intact cells. Using the interaction trap screen (active cytoplasmic domain of the IGF-IR) 55PIK and SOCS-2 proteins were also identified. However, 55PIK and SOCS-2 also interact with the IR in the yeast two hybrid system. These studies raise the possibility that 14-3-3 and Grb10 may play a role in insulin and IGF-I signal transduction and may underlie the observed differences.

3

Characterization of dual specificity protein kinase from maize seedlings

100%

Trojanek J. B., Klimecka M. M., Fraser A., Dobrowolska G., Muszynska G.

Acta Biochimica Polonica

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2004

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tom 51

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nr 3

A protein kinase of 57 kDa, able to phosphorylate tyrosine in synthetic substrates pol(Glu4,Tyr1) and a fragment of Src tyrosine kinase, was isolated and partly purified from maize seedlings (Zea mays). The protein kinase was able to phosphorylate exogenous proteins: enolase, caseins, histones and myelin basic protein. Amino acid analysis of phosphorylated casein and enolase, as well as of phosphorylated endogenous proteins, showed that both Tyr and Ser residues were phosphorylated. Phosphotyrosine was also immunodetected in the 57 kDa protein fraction. In the protein fraction there are present 57 kDa protein kinase and enolase. This co-purification suggests that enolase can be an endogenous substrate of the kinase. The two proteins could be resolved by two-dimensional electrophoresis. Specific inhibitors of typical protein-tyrosine kinases had essentially no effect on the activity of the maize enzyme. Staurosporine, a nonspecific inhibitor of protein kinases, effectively inhibited the 57 kDa protein kinase. Also, poly L-lysine and heparin inhibited tyrosine phosphorylation by 57 kDa maize protein kinase. The substrate and inhibitor specificities of the 57 kDa maize protein kinase phosphorylating tyrosine indicate that it is a novel plant dual-specificity protein kinase.

4

Participation of myosin I, spectrin analogue and tyrosine-phosphorylated proteins at early stages of phagocytosis in Acanthamoeba castellanii

86%

Kwiatkowska K., Sobota A.

Acta Protozoologica

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1998

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tom 37

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nr 4

5

Inhibitors of cyclin dependent protein kinases

86%

Fabbro D., Woods-Cook K., Solf R., Meyer T., Mett H., Geiger T., Furet P., Zimmermann J., Ruetz S.

Cellular and Molecular Biology Letters

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1998

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tom 03

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nr 3

6

The role of cholesterol and sphingomyelin in tyrosine phosphorylation of proteins and capping of Fc-gamma receptor II

86%

Drzewiecka A., Kwiatkowska K., Sobota A.

Acta Biochimica Polonica

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1999

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tom 46

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nr 1

Cross-linking of cell surface receptors by multivalent ligands, e.g. by antibodies, evokes their clustering - patching. Subsequently, these clusters can be translocated by the acto-myosin machinery toward one pole of the cell and assembly cap. Patching of FcγRII in U937 cells correlates with tyrosine phosphorylation of several proteins while cap assembly correlates with their dephosphorylation. To study the mechanism of activation of tyrosine kinases during FcγRII activation we disturbed the organization of the putative plasma membrane microdomains by depletion of membrane cholesterol and sphingomyelin. Cholesterol was removed with the use of β-cyclodextrin while sphingomyelin was decomposed by exogenous sphingomyelinase. Cyclodextrin at 5-10 mM removed about 70% of cholesterol from the cells and abolished the assembly of FcγRII caps thereby arresting the receptors at the patching stage. Similarly, 70 mU/ml sphingomyelinase inhibited cap formation by 60%. Cholesterol and sphingomyelin depletion also suppressed the tyrosine phosphorylation of proteins which accompanied cross-linking of FcγRII. The observations indicate that cholesterol and sphingomyelin can control the interactions of tyrosine kinases with clustered FcγRII.

7

Insulin-like growth factor I activates insulin receptor substrate 1 and Ras in human osteosarcoma cells

86%

Lopaczynski W., Terry C.

Acta Biochimica Polonica

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1999

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tom 46

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nr 1

Insulin-like growth factor I (IGF-I) stimulates multiplication of the human osteosarcoma cell line, MG-63, by acting through IGF-I receptor. We have characterized IGF-I stimulated phosphorylation of IRS-1, activation of Ras cycle and phosphorylation of c-Jun in this cell line. Serum starved MG-63 cells were (1) IGF-I stimulated and lysates were immunoprecipitated with polyclonal IRS-1 antibody or (2) metabolically labeled with [32P]orthophosphoric acid and then cells were treated with IGF-I. Cell lysates were immunoprecipitated with p21Ras antibody(Y13-259) and bound nucleotides were analysed by thin layer chromatography. We demonstrated tyrosine phosphorylation of IRS-1/2 immunoprecipitated from MG-63 cells stimulated with IGF-I. We also showed an increased level of GTP in p21Ras immunoprecipitates from IGF-I treated cells. Nuclear extracts prepared from 32P-labeled cells before and after addition of IGF-I were immunoprecipitated with c-Jun antibody. After electrophoresis and autoradiography, phosphorylation of the c-Jun band was seen to be IGF-I independent. Phosphoamino acid analysis of the c-Jun band showed that phosphoserine was the major species.

8

The interaction between L1-type proteins and ankyrins - a master switch for L1-type CAM functions

58%

Hortsch M., Nagaraj K., Godenschwege T. A.

Cellular and Molecular Biology Letters

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2009

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tom 14

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nr 1

57-69

L1-type cell adhesion molecules (CAMs) are important mediators of neural differentiation, including axonal outgrowth and pathfinding and also of synapse formation and maintenance. In addition, their interactions with cytoskeletal components are highly conserved and regulated. How these different aspects of CAM functionality relate to each other is not well understood. Based on results from our and other laboratories we propose that ankyrin-binding to L1-type CAMs provides a master switch. The interaction with ankyrins directs L1-type adhesive proteins into different functional contexts, either ankyrin-independent functions, such as neurite outgrowth and axonal pathfinding or into ankyrin-dependent functions, such as L1’s role at axon initial segments (AIS), paranodal regions, synapses and in dendrites.

Ograniczanie wyników

Participation of 125 kDa tyrosine-phosphorylated protein in phagocytosis of Acanthamoeba cells

Differential regulation of signalling pathways for insulin and insulin-like growth factor I

Characterization of dual specificity protein kinase from maize seedlings

Participation of myosin I, spectrin analogue and tyrosine-phosphorylated proteins at early stages of phagocytosis in Acanthamoeba castellanii

Inhibitors of cyclin dependent protein kinases

The role of cholesterol and sphingomyelin in tyrosine phosphorylation of proteins and capping of Fc-gamma receptor II

Insulin-like growth factor I activates insulin receptor substrate 1 and Ras in human osteosarcoma cells

The interaction between L1-type proteins and ankyrins - a master switch for L1-type CAM functions