Magnetic nanoparticles with surface modification enhanced gene delivery of HVJ-E vector

To enter the realm of human gene therapy, a novel drug delivery system is required for efficient delivery of small molecules with high safety for clinical usage. We have developed a unique vector "HVJ-E (hemagglutinating virus of Japan-envelope)" that can rapidly transfer plasmid DNA, oligonucleotide, and protein into cells by cell-fusion. In this study, we associated HVJ-E with magnetic nanoparticles, which can potentially enhance its transfection efficiency in the presence of a magnetic force. Magnetic nanoparticles, such as maghemite, with an average size of 29 nm, can be regulated by a magnetic force and basically consist of oxidized Fe which is commonly used as a supplement for the treatment of anemia. A mixture of magnetite particles with protamine sulfate, which gives a cationic surface charge on the maghemite particles, significantly enhanced the transfection efficiency in an in vitro cell culture system based on HVJ-E technology, resulting in a reduction in the required titer of HVJ. Addition of magnetic nanoparticles would enhance the association of HVJ-E with the cell membrane with a magnetic force. However, maghemite particles surface-coated with heparin, but not protamine sulfate, enhanced the transfection efficiency in the analysis of direct injection into the mouse liver in an in vivo model. The size and surface chemistry of magnetic particles could be tailored accordingly to meet specific demands of physical and biological characteristics. Overall, magnetic nanoparticles with different surface modifications can enhance HVJ-E-based gene transfer by modification of the size or charge, which could potentially help to overcome fundamental limitations to gene therapy in vivo.     

Fluorogenic substrates of glycogen debranching enzyme for assaying debranching activity

Glycogen debranching enzyme (GDE) degrades glycogen in concert with glycogen phosphorylase. GDE has two distinct active sites for maltooligosaccharide transferase and amylo-1,6-glucosidase activities. Phosphorylase limit dextrin from glycogen is debranched by cooperation of the two activities. Fluorogenic branched dextrins were prepared as substrates of GDE from pyridylaminated maltooctaose (PA-maltooctaose) and maltotetraose, taking advantage of the synthetic action of Klebsiella pneumoniae pullulanase. Their structures were as follows: Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4(Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-6)Glcalpha1-4Glcalpha1-4GlcPA (B3), Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4(Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-6)Glcalpha1-4Glcalpha1-4Glcalpha1-4GlcPA (B4), Glcalpha1-4Glcalpha1-4Glcalpha1-4(Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-6)Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4GlcPA (B5), Glcalpha1-4Glcalpha1-4(Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-6)Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4GlcPA (B6), Glcalpha1-4(Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-6)Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4GlcPA (B7), and Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-6Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4Glcalpha1-4GlcPA (B8). These dextrins were incubated with porcine skeletal muscle GDE. No fluorogenic product was found in the digest of B8. The fluorogenic products from B3, B4, and B5 were PA-maltooctaose only. PA-maltooctaose, PA-maltoundecaose, and 6(7)-O-alpha-glucosyl-PA-maltooctaose were from B7. PA-maltooctaose and 6(6)-O-alpha-glucosyl-PA-maltooctaose were from B6. These results indicate that the maltooligosaccharide transferase removed the maltotriosyl residues from the maltotetraosyl branches by hydrolysis or intramolecular transglycosylation to expose 6-O-alpha-glucosyl residues, and then the amylo-1,6-glucosidase hydrolyzed the alpha-1,6-glycosidic linkages of the products rapidly. Probably, 6-O-alpha-glucosyl-PA-maltooctaoses from B7 and B6 were less susceptible to the amylo-1,6-glucosidase than were those from B3, B4, and B5. Taking this into account, B3, B4, and B5 are suitable substrates for GDE assay.     

Paramagnetic NMR study of Cu(2+)-IDA complex localization on a protein surface and its application to elucidate long distance information

The paramagnetic metal chelate complex Cu(2+)-iminodiacetic acid (Cu(2+)-IDA) was mixed with ubiquitin, a small globular protein. Quantitative analyses of (1)H and (15)N chemical shift changes and line broadenings induced by the paramagnetic effects indicated that Cu(2+)-IDA was localized to a histidine residue (His68) on the ubiquitin surface. The distances between the backbone amide proton and the Cu(2+) relaxation center were evaluated from the proton transverse relaxation rates enhanced by the paramagnetic effect. These correlated well with the distances calculated from the crystal structure up to 20 A. Here, we show that a Cu(2+)-IDA is the first paramagnetic reagent that specifically localizes to a histidine residue on the protein surface and gives the long-range distance information.     

Mutual regulation of protein-tyrosine phosphatase 20 and protein-tyrosine kinase Tec activities by tyrosine phosphorylation and dephosphorylation

PTP20, also known as HSCF/protein-tyrosine phosphatase K1/fetal liver phosphatase 1/brain-derived phosphatase 1, is a cytosolic protein-tyrosine phosphatase with currently unknown biological relevance. We have identified that the nonreceptor protein-tyrosine kinase Tec-phosphorylated PTP20 on tyrosines and co-immunoprecipitated with the phosphatase in a phosphotyrosine-dependent manner. The interaction between the two proteins involved the Tec SH2 domain and the C-terminal tyrosine residues Tyr-281, Tyr-303, Tyr-354, and Tyr-381 of PTP20, which were also necessary for tyrosine phosphorylation/dephosphorylation. Association between endogenous PTP20 and Tec was also tyrosine phosphorylation-dependent in the immature B cell line Ramos. Finally, the Tyr-281 residue of PTP20 was shown to be critical for deactivating Tec in Ramos cells upon B cell receptor ligation as well as dephosphorylation and deactivation of Tec and PTP20 itself in transfected COS7 cells. Taken together, PTP20 appears to play a negative role in Tec-mediated signaling, and Tec-PTP20 interaction might represent a negative feedback mechanism.     

Casein kinase 1alpha interacts with retinoid X receptor and interferes with agonist-induced apoptosis

Agonists of retinoid X receptors (RXRs), which include the natural 9-cis-retinoic acid and synthetic analogs, are potent inducers of growth arrest and apoptosis in some cancer cells. As such, they are being used in clinical trials for the treatment and prevention of solid tumors and are used to treat cutaneous T cell lymphoma. However, the molecular mechanisms that underlie the anti-cancer effects of RXR agonists remain unclear. Here, we show that a novel pro-apoptotic pathway that is induced by RXR agonist is negatively regulated by casein kinase 1alpha (CK1alpha). CK1alpha associates with RXR in an agonist-dependent manner and phosphorylates RXR. The ability of an RXR agonist to recruit CK1alpha to a complex with RXR in cells correlates inversely with its ability to inhibit growth. Remarkably, depletion of CK1alpha in resistant cells renders them susceptible to RXR agonist-induced growth inhibition and apoptosis. Our study shows that CK1alpha can promote cell survival by interfering with RXR agonist-induced apoptosis. Inhibition of CK1alpha may enhance the anti-cancer effects of RXR agonists.     

Neuronal roles of the integrin-associated protein (IAP/CD47) in developing cortical neurons

Little is known about the role of the integrin-associated protein (IAP, or CD47) in neuronal development and its function in the central nervous system. We investigated neuronal responses in IAP-overexpressing cortical neurons using a virus-gene transfer system. We found that dendritic outgrowth was significantly enhanced in IAP (form 4)-transfected neurons. Furthermore, synaptic proteins including synaptotagmin, syntaxin, synapsin I, and SNAP25 (25-kDa synaptosomal associated protein) were up-regulated. In accordance with this finding, the release of the excitatory transmitter glutamate and the frequencies of Ca2+ oscillations (glutamate-mediated synaptic transmission) were increased. Interestingly, the overexpression of IAP activated mitogen-activated protein kinase (MAPK), and this activation was required for the IAP-dependent biological effects. After down-regulation of the endogenous IAP by small interfering RNA, MAPK activity, synaptic protein levels, and glutamate release decreased. These observations suggest that the IAP plays important roles in dendritic outgrowth and synaptic transmission in developing cortical neurons through the activation of MAPK.     

Inhibition of poly (ADP-ribose) polymerase and caspase-3, but not caspase-1, prevents apoptosis and improves spatial memory of rats with twice-repeated cerebral ischemia

The effect of inhibition of PARP [(poly (ADP-ribose) polymerase], caspase-3 and caspase-1 on twice-repeated ischemia-induced apoptosis and memory impairment were examined. The twice repeated ischemia was induced by four-vessel occlusion method in which a 10 min ischemic episode was repeated once after 60 min. The spatial memory was assessed using 8-arm radial maze. The results of this study showed that the repeated ischemia impaired memory and induced apoptosis in hippocampus CA1 field after 7 days. Moreover, 3-aminobezamide (10 mg/kg i.v.), a PARP inhibitor, and Ac-DEVD-CHO (8.4 microg/5 microL i.c.v., bilaterally), a caspase-3 inhibitor, decreased apoptosis by 45% and 58% respectively. Both drugs reduced the error choices, but 3-aminobezamide additionally increased the correct choices and improved the memory when either drug was injected immediately after the ischemic insult. The results also showed that inhibition of interleukin-1beta-converting enzyme, ICE (caspase-1) by Z-ASP-DCB-CH2 (100 microg/kg i.c.v., bilaterally) neither decreased apoptosis (13% reduction) nor improved memory of the ischemic rats. These results suggest that direct inhibition of PARP and caspase-3, but not of caspase-1, prevents apoptosis and improves spatial memory impaired by repeated ischemia.     

Structural analysis of the ZEN-4/CeMKLP1 motor domain and its interaction with microtubules

The centralspindlin complex is required for the assembly and maintenance of the central spindle during late anaphase and the completion of cytokinesis. It is composed of two copies each of the kinesin-like protein ZEN-4, a Caenorhabditis elegans MKLP-1 (Kinesin-6 family), and the RhoGAP CYK-4. By using cryo-electron microscopy and helical 3D reconstruction, we are investigating the structural features of the interactions between monomeric and dimeric motor domain constructs of ZEN-4 and microtubules. We have calculated helically averaged 3D maps of microtubules decorated with ZEN-4 motor domain in the presence of AMP-PNP, ADP, ADP-AlF(4)(-), and nucleotide-free conditions. We used statistical difference mapping to compare these maps among each other and to related maps obtained from microtubules decorated with a well-characterized Kinesin-1 motor domain from Neurospora crassa. Thereby, we found distinct structural features in microtubule-ZEN-4 complexes that may directly relate to the functional properties of ZEN-4 and centralspindlin. Furthermore, we investigated the location, structure, and function of a highly conserved extension of approximately 50 residues unique to the Kinesin-6 subfamily, located in the motor core loop6/beta4 region.