Cationized ferritin and phosvitin uptake by coated vesicles of the early chick embryo

A suitable and effective stepwise oxidative refolding procedure for highly-cationic tetrameric avidin in nucleic acid free conditions

Optimized conditions are needed to refold recombinant proteins from bacterial inclusion bodies into their biologically active conformations. In this study, we found two crucial requirements for efficient refolding of cationic tetrameric chicken avidin. The first step is to eliminate nucleic acid contaminants from the bacterial inclusion body. The electrostatic interactions between the remaining nucleic acids and proteins strongly enhanced protein aggregation during the refolding process. The cysteine specific reversible S-cationization procedure was successfully employed for large-scale preparation of nucleic acid free denatured protein without purification tag system. The second step is the intramolecular disulfide formation prior to refolding in dialysis removing denaturant. Disulfide intact monomeric avidin showed efficient formation of biologically active tetrameric conformation during the refolding process. Using this optimized refolding procedure, highly cationic avidin derivative designed as an intracellular delivery carrier of biotinylated protein was successfully prepared.

Synthesis of Cationized Magnetoferritin for Ultra-fast Magnetization of Cells

Many important biomedical applications, such as cell imaging and remote manipulation, can be achieved by labeling cells with superparamagnetic iron oxide nanoparticles (SPIONs). Achieving sufficient cellular uptake of SPIONs is a challenge that has traditionally been met by exposing cells to elevated concentrations of SPIONs or by prolonging exposure times (up to 72 hr). However, these strategies are likely to mediate toxicity. Here, we present the synthesis of the protein-based SPION magnetoferritin as well as a facile surface functionalization protocol that enables rapid cell magnetization using low exposure concentrations. The SPION core of magnetoferritin consists of cobalt-doped iron oxide with an average particle diameter of 8.2 nm mineralized inside the cavity of horse spleen apo-ferritin. Chemical cationization of magnetoferritin produced a novel, highly membrane-active SPION that magnetized human mesenchymal stem cells (hMSCs) using incubation times as short as one minute and iron concentrations as lows as 0.2 mM.

Novel bioactivity of phosvitin in connective tissue and bone organogenesis revealed by live calvarial bone organ culture models

Egg yolk phosvitin is one of the most highly phosphorylated extracellular matrix proteins known in nature with unique physico-chemical properties deemed to be critical during ex-vivo egg embryo development. We have utilized our unique live mouse calvarial bone organ culture models under conditions which dissociates the two bone remodeling stages, viz., resorption by osteoclasts and formation by osteoblasts, to highlight important and to date unknown critical biological functions of egg phosvitin. In our resorption model live bone cultures were grown in the absence of ascorbate and were stimulated by parathyroid hormone (PTH) to undergo rapid osteoclast formation/differentiation with bone resorption. In this resorption model native phosvitin potently inhibited PTH-induced osteoclastic bone resorption with simultaneous new osteoid/bone formation in the absence of ascorbate (vitamin C). These surprising and critical observations were extended using the bone formation model in the absence of ascorbate and in the presence of phosvitin which supported the above results. The results were corroborated by analyses for calcium release or uptake, tartrate-resistant acid phosphatase activity (marker for osteoclasts), alkaline phosphatase activity (marker for osteoblasts), collagen and hydroxyproline composition, and histological and quantitative histomorphometric evaluations. The data revealed that the discovered bioactivity of phosvitin mirrors that of ascorbate during collagen synthesis and the formation of new osteoid/bone. Complementing those studies use of the synthetic collagen peptide analog and cultured calvarial osteoblasts in conjunction with mass spectrometric analysis provided results that augmented the bone organ culture work and confirmed the capacity of phosvitin to stimulate differentiation of osteoblasts, collagen synthesis, hydroxyproline formation, and biomineralization. There are striking implications and interrelationships of this affect that relates to the evolutionary inactivation of the gene of an enzyme L-gulono-γ-lactone oxidase, which is involved in the final step of ascorbate biosynthesis, in many vertebrate species including passeriform birds, reptiles and teleost fish whose egg yolk contain phosvitin. These represent examples of how developing ex-vivo embryos of such species can achieve connective tissue and skeletal system formation in the absence of ascorbate.

Endocytosis of horse-spleen ferritin by bony fish endocardium

The endocytic uptake of horse-spleen ferritin by the endocardial cells in 2 bony-fish species, Xiphophorus helleri and Pollachius virens, is described. In specimens of X. helleri injected intraperitoneally by a ferritin solution 1/10 h before the sacrifice, the endocardial bristle-coated vesicles, cytoplasmic tubules, and endosomes (smooth vesicles of variable size) contain a number of ferritin particles. These particles are taken up by the bristle-coated vesicles, transferred through the cytoplasmic tubules, and emptied into the endosomes. The latter get more tightly packed by ferritin and increase in size with the time elapsed between the injection and sacrifice. After 9 h, most ferritin-packed endosomes (4 to 6 micron) contain fragments of those inclusion bodies (0.5 to 1.5 micron) which normally occur in the teleostean endocardium, and are therefore regarded as lysosomes. The ferritin-rich lysosomes increase greatly in size with time and display a width of 6 to 12 micron after 28 h. The number of cytoplasmic tubules declines rapidly with time, whereas there is a constant production of new endosomes, which probably are derived from the former. The ferritin particles are not accumulated in the endothelium of the bulbus arteriosus, whereas the hepatic endothelial cells take up some small amounts of ferritin. A similar uptake of ferritin as described above was also observed in the heart of P. virens when perfused by a ferritin solution for 3 h. The present results are discussed and compared with those previously reported for the uptake of ferritin in various tissues in fishes and mammals.(ABSTRACT TRUNCATED AT 250 WORDS)