A novel apoptosis probe, cyclic ApoPep-1, for in vivo imaging with multimodal applications in chronic inflammatory arthritis

Apoptosis plays an essential role in the pathophysiologic processes of rheumatoid arthritis. A molecular probe that allows spatiotemporal observation of apoptosis in vitro, in vivo, and ex vivo concomitantly would be useful to monitoring or predicting pathophysiologic stages. In this study we investigated whether cyclic apoptosis-targeting peptide-1 (_CApoPep-1) can be used as an apoptosis imaging probe in inflammatory arthritis. We tested the utility of _CApoPep-1 for detecting apoptotic immune cells in vitro and ex vivo using flow cytometry and immunofluorescence. The feasibility of visualizing and quantifying apoptosis using this probe was evaluated in a murine collagen-induced arthritis (CIA) model, especially after treatment. _CApoPep-1 peptide may successfully replace Annexin V for in vitro and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay for ex vivo in the measurement of apoptotic cells, thus function as a sensitive probe enough to be used clinically. In vivo imaging in CIA mice revealed that _CApoPep-1 had 42.9 times higher fluorescence intensity than Annexin V for apoptosis quantification. Furthermore, it may be used as an imaging probe for early detection of apoptotic response in situ after treatment. The _CApoPep-1 signal was mostly co-localized with the TUNEL signal (69.6% of TUNEL⁺ cells) in defined cell populations in joint tissues of CIA mice. These results demonstrate that _CApoPep-1 is sufficiently sensitive to be used as an apoptosis imaging probe for multipurpose applications which could detect the same target across in vitro, in vivo, to ex vivo in inflammatory arthritis.

Designed nanocage displaying ligand-specific Peptide bunches for high affinity and biological activity

Protein-cage nanoparticles are promising multifunctional platforms for targeted delivery of imaging and therapeutic agents owing to their biocompatibility, biodegradability, and low toxicity. The major advantage of protein-cage nanoparticles is the ability to decorate their surfaces with multiple functionalities through genetic and chemical modification to achieve desired properties for therapeutic and/or diagnostic purposes. Specific peptides identified by phage display can be genetically fused onto the surface of cage proteins to promote the association of nanoparticles with a particular cell type or tissue. Upon symmetrical assembly of the cage, peptides are clustered on the surface of the cage protein in bunches. The resulting PBNC (peptide bunches on nanocage) offers the potential of synergistically increasing the avidity of the peptide ligands, thereby enhancing their blocking ability for therapeutic purposes. Here, we demonstrated a proof-of-principle of PBNCs, fusing the interleukin-4 receptor (IL-4R)-targeting peptide, AP-1, identified previously by phage display, with ferritin-L-chain (FTL), which undergoes 24-subunit assembly to form highly stable AP-1-containing nanocage proteins (AP1-PBNCs). AP1-PBNCs bound specifically to the IL-4R-expressing cell line, A549, and their binding and internalization were specifically blocked by anti-IL-4R antibody. AP1-PBNCs exhibited dramatically enhanced binding avidity to IL-4R compared with AP-1 peptide, measured by surface plasmon resonance spectroscopy. Furthermore, treatment with AP1-PBNCs in a murine model of experimental asthma diminished airway hyper-responsiveness and eosinophilic airway inflammation along with decreased mucus hyperproduction. These findings hold great promise for the application of various PBNCs with ligand-specific peptides in therapeutics for different diseases, such as cancer.

Abstract 343: High-throughput screening of multiple protein kinase inhibitor using polymeric nanoparticles

Protein kinase play pivotal regulatory roles in most cell communication and metabolic pathways. Inhibitors of protein kinases not only hold great promise as therapeutic agents for many diseases, especially cancer, but are also of profound utility in the characterization of signaling pathways because of the centrality of protein phosphorylation as a regulatory process. Therefore, sensitive and widely applicable detection of protein kinase activity will provide a valuable tool to screen protein kinase inhibitors in drug discovery. We previously reported that self-assembled poly-ion complexes (PICs) containing kemptide, protein kinase A specific peptide motif, recognize the phosphorylation of kemptide by protein kinase A by recovery of fluorescence. In this research we found kinase specific substrate peptide with phage display which an efficient primary screening method to detect protein-protein interaction because of its relatively easy, rapid and massive recovery and analysis. Kinase substrate peptide library was made with phage and then library is displayed on capsid protein of phage. After kinase reaction, the phage clones are selected, recovered, and amplified for next round of bio-panning. The candidate clones are selected according for at least 4th round of bio-panning and the resultant peptides are analyzed for specificity. To prepare PICs, found peptide was conjugated with polyehtyleneimine (PEI) labeled with cyanine 5.5 (cy5.5). PICs consisting of peptide and cy5.5 chemically conjugated PEI and poly-L-aspartic acid showed significant fluorescent signal recovery in presence of protein kinase while they hardly showed fluorescent signal in absence of protein kinase. In addition, fluorescent signal did not recover with protein kinase inhibitor even though protein kinase was present. We tried to apply highthroughput screening to perform chemical library screening with 384-well plate. While wells without protein kinase showed strong fluorescent signal, wells containing protein kinase inhibitors represented no fluorescent signal, which is fully consistent with previous results and our expects. We conclude that this system is applied to highthroughput screening systems targeting protein kinase inhibitors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 343.

Thymosin beta4 is involved in stabilin-2-mediated apoptotic cell engulfment

Stabilin-2 was recently identified as a novel receptor for membrane phosphatidylserine of apoptotic cells. To identify proteins that were candidates for stabilin-2 cytoplasmic domain binding, we screened a human spleen cDNA library using the yeast two-hybrid system. We found that thymosin beta4 interacts with the stabilin-2 cytoplasmic domain and is co-localized with stabilin-2 at the phagocytic cup. Knockdown of thymosin beta4 significantly decreased the phagocytic activity of stabilin-2, whereas overexpression of thymosin beta4 increased this activity. Additionally, amino acids 2504-2514 of stabilin-2 cytoplasmic domain were found to be responsible for the interaction with thymosin beta4. Taken together, these results suggest that thymosin beta4 is a downstream molecule of stabilin-2 that plays a role in stabilin-2-mediated cell corpse clearance.

1,4-dioxane-fused 4-anilinoquinazoline as inhibitors of epidermal growth factor receptor kinase

The 4-anilinoquinazoline PD 153035 (1) is a potential antitumor agent which acts by inhibiting tyrosine kinase activity of epidermal growth factor receptor (EFGR) via competitive binding at the ATP site of enzyme. A series of cyclic analogues of PD 153035 bearing the 1,4-dioxane ring was prepared by reaction of 6-chloro derivative 5 with several aniline nucleophiles. These were evaluated for their ability to inhibit the EGFR kinase and the growth of primary human tumor cell cultures. All of the new 4-anilinoquinazolines exhibited less potency than PD 153035 against EGFR kinase. However, compounds 2b, 2c, 2e, 2g, and 2h showed higher inhibitory activities than PD 153035 against the growth of A431 tumor cell line. The compound 2b containing 3-chloroaniline ring was as potent as PD 153035 against EGFR kinase and showed about 5.4-fold better potency than PD153035 in the inhibition of growth of A431 cell line with good selectivity.

Induction of early flowering in Cymbidium niveo-marginatum Mak in vitro

 Many orchids take several years to flower. We have been able to induce early flowering in the temperate orchid Cymbidium niveo-marginatum Mak in vitro. The combined treatment of cytokinin (6-benzylaminopurine), restricted nitrogen supply with phosphorus enrichment, and root excision (pruning) induced transition of the Cymbidium shoot from a vegetative to a reproductive stage. Nearly 100% of the plants flowered within 90 days only when the combined treatment was applied. When root excision and/or 6-benzylaminopurine were omitted from the combined treatments, flower induction was significantly reduced. The auxin transport inhibitor, 2,3,5-triiodobenzoic acid prevented flowering of Cymbidium in vitro, although auxin (α-naphthaleneacetic acid) itself did not induce flowering. Gibberellic acid markedly delayed flowering in C. niveo-marginatum even when the flower-promoting treatment was applied. Paclobutrazol, an anti-gibberellin agent, totally blocked the inductive effects of either cytokinin or pruning. These observations suggest that concerted actions of auxin, cytokinin, and gibberellin, as well as nutrient concentration and putative promoting/suppressing agents, determine the timing of Cymbidium orchid transition from the vegetative to reproductive stage.

Molecular cloning and characterization of the Saccharomyces cerevisiae SAB1 gene that suppresses a temperature-sensitive phenotype of the ARS-binding factor 1 mutant

A high-copy number suppressor gene of the yeast temperature-sensitive lethal abf1 mutant was isolated and named SAB1 (suppressor of ABF1). Chromoblot hybridization and grid-filter hybridization analyses showed that the SAB1 gene was located on chromosome IV. Deletion analyses of the SAB1 plasmid revealed that the suppressor activity was contained in a 1.1 kb DNA region. The nucleotide sequence of the 1.1 kb DNA fragment was determined and turned out to be identical to that of the yeast phosphoribosylanthranilate isomerase gene (TRP1). A binding site for ARS-Binding Factor 1 was located in the coding sequence of the TRP1 gene, which has been known to be a part of the B domain of yeast autonomously replicating sequence 1 (ARS1). Our results suggest that ABF1 might be important for the transcription of the yeast TRP1 gene in addition to having important roles in the stimulation of replication at the ARS1 locus.

Isolation and characterization of Saccharomyces cerevisiae SAB2, a suppressor gene for temperature-sensitive phenotype of ARS-binding factor 1 mutant

A high-copy number suppressor of yeast abf1-5 mutant, a temperature-sensitive lethal mutant, was isolated and named SAB2 (suppressor of ABF1). Hybridization to a yeast chromoblot and to prime clone grid filters revealed that the SAB2 gene was located near the yeast SUP3 on chromosome XV. The suppressor activity was contained in a 2.5 Kbp DNA region of the SAB2 plasmid. The nucleotide sequence of the DNA region contained a long open reading frame, which turned out to encode for yeast tryptophan permease. Four putative ABF1 binding sites were found in the promoter and the structural regions of the tryptophan permease gene. Binding of ABF1 to two of the sites tested in this study was detected. Our results indicate that ABF1 may be involved in the transcriptional control of the yeast tryptophan permease gene.

Inward current generated by Na-Ca exchange during the action potential in single atrial cells of the rabbit

To investigate the underlying ionic mechanism of the late plateau phase of the action potential in rabbit atrium the whole-cell patch-clamp technique with intracellular perfusion was used. We recorded the inward current during repolarizations following a brief 2 ms depolarizing pulse to +40 mV from a holding potential of between -70 and -80 mV. The development of this current coincides with the onset of the late plateau phase of the action potential. Peak activation of the current occurs about 10 ms from the beginning of the depolarizing pulse, and it decays spontaneously with a slow timecourse. Its voltage dependency from -40 mV to +40 mV shows very steep activation (-40 to -20 mV) and shows almost the same maximum magnitude between -10 mV and +40 mV. This behaviour is quite different from that of the calcium current. The inward current and the late plateau phase of the action potential were both abolished by the application of 5 mM EGTA, 1 microM ryanodine and by reducing the Na+ gradient. The fully activated current-voltage relation of the inward current was plotted as the difference current before and after treatment with Ryanodine, Diltiazem, 20 mM Na+ inside or 30% Na+ outside and shows an exponential voltage dependence with the largest magnitude of the current occurring at negative potentials. The current-voltage (I-V) curve was well fitted by the Na-Ca exchange equation, i = A exp (-(1 - r)EF/RT). The results suggest that the inward current contributes to the generation of the late plateau phase of the rabbit atrial action potential, and is activated by intracellular calcium released from the sarcoplasmic reticulum. Sarcoplasmic reticulum calcium release appears to be triggered both by the membrane voltage and by the calcium current. It is concluded that the inward current is generated by Na-Ca exchange.