Piotr Jakimowicz

Rhodium(III) complexes with polypyridyls and pyrazole and their antitumor activity

Abstract Synthesis and properties of rhodium complexes with nitrogen ligands [RhCl 2 (Hpz) 4 ][RhCl 4 (Hpz) 2 ] ( 1 ), [RhCl 3 (tpy)] ( 2 ), [RhCl 3 (tpta)]·H 2 O ( 3 ) and [Rh(tpy) 2 (Him)]Cl 3 ·3H 2 O ( 4 ), have been described. X-ray structures of complexes 1 – 3 have been determined. IR, UV–Vis and 1 H NMR spectra of the complexes have been discussed. Cytostatic activity of the complexes against HCV29T tumor cells increases in the series: 1 3 2 4 . The cytostatic activity of complex 4 is greater than that of cisplatin. Interaction of the complexes with DNA has been investigated.

Rhodium wires based on binuclear acetate-bridged complexes

Abstract The synthesis, properties, structure and conductivity of a new class of one-dimensional, mixed valence Rh(I)–Rh(II) complexes { Rh 2 ( μ-O 2 CMe ) 2 ( N – N ) 2 ][ BX 4 ]} n ( N – N =bipyridine, phenanthroline; X=F, Ph) are described.

UDP-N-acetylglucosamine transporter (SLC35A3) regulates biosynthesis of highly branched N-glycans and keratan sulfate.

Background: Knowledge regarding UDP-N-acetylglucosamine transporter (NGT; SLC35A3) is incomplete due to the lack of NGT-deficient model cell lines. Results: The siRNA approach showed that NGT silencing reduces branching of complex N-glycans and keratan sulfate synthesis. Conclusion: NGT function may be coupled to the specific glycosylation pathway(s) of particular macromolecules. Significance: Our results add to the understanding of glycosylation, one of the basic posttranslational modifications. SLC35A3 is considered the main UDP-N-acetylglucosamine transporter (NGT) in mammals. Detailed analysis of NGT is restricted because mammalian mutant cells defective in this activity have not been isolated. Therefore, using the siRNA approach, we developed and characterized several NGT-deficient mammalian cell lines. CHO, CHO-Lec8, and HeLa cells deficient in NGT activity displayed a decrease in the amount of highly branched tri- and tetraantennary N-glycans, whereas monoantennary and diantennary ones remained unchanged or even were accumulated. Silencing the expression of NGT in Madin-Darby canine kidney II cells resulted in a dramatic decrease in the keratan sulfate content, whereas no changes in biosynthesis of heparan sulfate were observed. We also demonstrated for the first time close proximity between NGT and mannosyl (α-1,6-)-glycoprotein β-1,6-N-acetylglucosaminyltransferase (Mgat5) in the Golgi membrane. We conclude that NGT may be important for the biosynthesis of highly branched, multiantennary complex N-glycans and keratan sulfate. We hypothesize that NGT may specifically supply β-1,3-N-acetylglucosaminyl-transferase 7 (β3GnT7), Mgat5, and possibly mannosyl (α-1,3-)-glycoprotein β-1,4-N-acetylglucosaminyltransferase (Mgat4) with UDP-GlcNAc.

Tumor-specific hyperthermia with aptamer-tagged superparamagnetic nanoparticles.

Targeted therapy is a method owing to its limited side effect profile, particularly in cancer treatment. Magnetic hyperthermia, which is induced by nanoparticles (NPs) conjugated with targeting agents, can be useful in combination with chemo- or radiotherapy. In this paper, we constructed dextran-coated ferric oxide NPs conjugated with specific anti-human epidermal growth factor receptor (HER2) aptamer and used them to induce magnetic hyperthermia in cultured cells. The specificity of the tagged NPs was determined by studying their effect relative to that of non-tagged NPs against two cell lines: human adenocarcinoma SK-BR3, overexpressing the HER2 receptor; and U-87 MG, a human glioblastoma epithelial cell line, not expressing HER2. In order to confirm the interaction of the tagged NPs with the cells we used, fluorescence microscopy and fluorescence-activated cell sorting analysis were performed. All of these experiments showed that the aptamer-tagged NPs were highly specific toward the HER2-expressing cells. In addition, a ninetyfold lower dose of the tagged NPs relative to that of the non-tagged NPs was needed to achieve ~50% cell killing by hyperthermia of the SK-BR3 cell line, while for the U-87 MG cells the viability level was close to 100%. These results show that targeted NPs can be applied at substantially lower doses than non-targeted ones to achieve similar effects of hyperthermia, which should greatly limit the side effects of treatment.

Synthesis and structural characterization of new one-dimensional rhodium complexes

New one-dimensional Rh I –Rh II complexes [Rh 2 (OOCMe) 2 (phen) 2 ] n (PF 6 ) n ·0.5 n Me 2 CHOH, and [Rh 2 (OOCMe) 2 (bpy) 2 ] n (PF 6 ) n · n H 2 O, have been synthesized and characterized. The compound is molecular wire with the shortest Rh(I)–Rh(II) distances, anions and solvate molecules occupy channels between parallel cationic wires.

Femtomolar Zn(II) affinity of minimal zinc hook peptides – a promising small tag for protein engineering

The minimal zinc hook peptide of Rad50 and its alanine mutants form highly stable Zn(II) complexes. These peptides were successfully used as a small, efficient tag for reversible Zn(II)-mediated protein homodimerization. The high stability, its biological consequences and potential applications in protein engineering are discussed.

FGF1-gold nanoparticle conjugates targeting FGFR efficiently decrease cell viability upon NIR irradiation

Fibroblast growth factor receptors (FGFRs) are overexpressed in a wide variety of tumors, such as breast, bladder, and prostate cancer, and therefore they are attractive targets for different types of anticancer therapies. In this study, we designed, constructed, and characterized FGFR-targeted gold nanoconjugates suitable for infrared-induced thermal ablation (localized heating leading to cancer cell death) based on gold nanoparticles (AuNPs). We showed that a recombinant ligand of all FGFRs, human fibroblast growth factor 1 (FGF1), can be used as an agent targeting covalently bound AuNPs to cancer cells overexpressing FGFRs. To assure thermal stability, protease resistance, and prolonged half-life of the targeting protein, we employed highly stable FGF1 variant that retains the biological activities of the wild type FGF1. Novel FGF1 variant, AuNP conjugates are specifically internalized only by the cells expressing FGFRs, and they significantly reduce their viability after irradiation with near-infrared light (down to 40% of control cell viability), whereas the proliferation potential of cells lacking FGFRs is not affected. These results demonstrate the feasibility of FGF1-coated AuNPs for targeted cancer therapy.

Overexpression of UDP-GlcNAc transporter partially corrects galactosylation defect caused by UDP-Gal transporter mutation

Nucleotide sugar transporters deliver substrates for glycosyltransferases into the endoplasmic reticulum and the Golgi apparatus. We demonstrated that overexpression of UDP‐GlcNAc transporter (NGT) in MDCK‐RCAr and CHO‐Lec8 mutant cells defective in UDP‐Gal transporter (UGT) restored galactosylation of N‐glycans. NGT overexpression resulted in decreased transport of UDP‐GlcNAc into the Golgi vesicles. This effect resembled the phenotype of mutant cells corrected by UGT1 overexpression. The transport of UDP‐Gal was not significantly changed. Our data suggest that the biological function of UGT and NGT in galactosylation of macromolecules may be coupled.

Efficient production and purification of extracellular domain of human FGFR-Fc fusion proteins from Chinese hamster ovary cells.

The family of fibroblast growth factor receptors (FGFRs) plays an important role in cell growth, survival, differentiation and angiogenesis. The three immunoglobulin-like extracellular domains of FGFR (D1, D2, and D3) are critical for ligand binding and specificity towards fibroblast growth factor and heparan sulfate. Fibroblast growth factor receptors are overexpressed in a wide variety of tumors, such as breast, bladder, and prostate cancer, and therefore they are attractive targets for different types of anticancer therapies. In this study, we have cloned, expressed in CHO cells and purified Fc-fused extracellular domains of different types of FGFRs (ECD_FGFR1a-Fc, ECD_FGFR1b-Fc, ECD_FGFR2a-Fc, ECD_FGFR2b-Fc, ECD_FGFR3a-Fc, ECD_FGFR3b-Fc, ECD_FGFR4a-Fc, ECD_FGFR4b-Fc), which could be used as molecular targets for the selection of specific antibodies. The fusion proteins were analyzed using gel electrophoresis, Western blotting and mass spectrometry. To facilitate their full characterization, the fusion proteins were deglycosylated using PNGase F enzyme. With an optimized transient transfection protocol and purification procedure we were able to express the proteins at a high level and purify them to homogeneity.

UDP-Gal/UDP-GlcNAc chimeric transporter complements mutation defect in mammalian cells deficient in UDP-Gal transporter.

The role of UDP-galactose transporter (UGT; SLC35A2) and UDP-N-acetylglucosamine transporter (NGT; SLC35A3) in glycosylation of macromolecules may be coupled and either of the transporters may partially replace the function played by its partner. The aim of this study was to construct chimeric transporters composed of the N-terminal portion of human NGT and the C-terminal portion of human UGT1 or UGT2 (NGT-UGT1 or NGT-UGT2, respectively), as well as of the N-terminal portion of UGT and C-terminal portion of NGT (UGT-NGT), overexpress them stably in UGT-deficient CHO-Lec8 and MDCK-RCA(r) cells, and characterize their involvement in glycosylation. Two chimeric proteins, NGT-UGT1 and NGT-UGT2, did not overexpress properly. In contrast, UGT-NGT chimeric protein was successfully overexpressed and localized properly to the Golgi apparatus. UGT-NGT chimeric transporter delivered UDP-Gal to the Golgi vesicles of UGT-deficient cells, which resulted in the increased content of galactosylated structures to such an extent that the wild-type phenotypes were completely restored. Our data further support our hypothesis that UGT and NGT cooperate in the UDP-Gal delivery for glycosyltransferases located in the Golgi apparatus. In a wider context, the results gained in this study add to our understanding of glycosylation, one of the basic posttranslational modifications, which affects the majority of macromolecules.