Introduction of the green fluorescent protein gene into hematopoietic stem cells results in prolonged discrepancy of in vivo transduction levels between bone marrow progenitors and peripheral blood cells in nonhuman primates

Background

The green fluorescent protein (GFP) has proven a useful marker in retroviral gene transfer studies targeting hematopoietic stem cells (HSCs) in mice. However, several investigators have reported very low in vivo peripheral blood marking levels in nonhuman primates after transplantation of HSCs transduced with the GFP gene. We retrovirally marked cynomolgus monkey HSCs with the GFP gene, and tracked in vivo marking levels within both bone marrow progenitor cells and mature peripheral blood cells following autologous transplantation after myeloablative conditioning.

Methods

Bone marrow cells were harvested from three cynomolgus macaques and enriched for the primitive fraction by CD34 selection. CD34⁺ cells were transduced with one of three retroviral vectors all expressing the GFP gene and were infused after myeloablative total body irradiation (500 cGy × 2). Following transplantation, proviral levels and fluorescence were monitored among clonogenic bone marrow progenitors and mature peripheral blood cells.

Results

Although 13–37% of transduced cells contained the GFP provirus and 11–13% fluoresced ex vivo, both provirus and fluorescence became almost undetectable in the peripheral blood within several months after transplantation regardless of the vectors used. However, on sampling of bone marrow at multiple time points, significant fractions (5–10%) of clonogenic progenitors contained the provirus and fluoresced ex vivo reflecting a significant discrepancy between GFP gene marking levels within bone marrow cells and their mature peripheral blood progeny. The discrepancy (at least one log) persisted for more than 1 year after transplantation. Since no cytotoxic T lymphocytes against GFP were detected in the animals, an immune response against GFP is an unlikely explanation for the low levels of transduced peripheral blood cells. Administration of granulocyte colony stimulating factor and stem cell factor resulted in mobilization of transduced bone marrow cells detectable as mature granulocyte progeny which expressed the GFP gene, suggesting that transduced progenitor cells in bone marrow could be mobilized into the peripheral blood and differentiated into granulocytes.

Conclusions

Low levels of GFP‐transduced mature cells in the peripheral blood of nonhuman primates may reflect a block to differentiation associated with GFP; this block can be overcome in part by nonphysiological cytokine treatment ex vivo and in vivo. Copyright © 2002 John Wiley & Sons, Ltd.

     

Integrating 'top-down" and "bottom-up" mass spectrometric approaches for proteomic analysis of Shewanella oneidensis

Here we present a comprehensive method for proteome analysis that integrates both intact protein measurement ("top-down") and proteolytic fragment characterization ("bottom-up") mass spectrometric approaches, capitalizing on the unique capabilities of each method. This integrated approach was applied in a preliminary proteomic analysis of Shewanella oneidensis, a metal-reducing microbe of potential importance to the field of bioremediation. Cellular lysates were examined directly by the "bottom-up" approach as well as fractionated via anion-exchange liquid chromatography for integrated studies. A portion of each fraction was proteolytically digested, with the resulting peptides characterized by on-line liquid chromatography/tandem mass spectrometry. The remaining portion of each fraction containing the intact proteins was examined by high-resolution Fourier transform mass spectrometry. This "top-down" technique provided direct measurement of the molecular masses for the intact proteins and thereby enabled confirmation of post-translational modifications, signal peptides, and gene start sites of proteins detected in the "bottom-up" experiments. A total of 868 proteins from virtually every functional class, including hypotheticals, were identified from this organism.     

Inhibition of hepatitis C virus NS3 protease by peptides derived from complementarity-determining regions (CDRs) of the monoclonal antibody 8D4: tolerance of a CDR peptide to conformational changes of a target

Somatic angiotensin-converting enzyme (ACE) consists of two homologous domains, each domain bearing a catalytic site. Differential scanning calorimetry of the enzyme revealed two distinct thermal transitions with melting points at 55.3 and 70.5 degrees C. which corresponded to denaturation of C- and N-domains, respectively. Different heat stability of the domains underlies the methods of acquiring either single active N-domain or active N-domain with inactive C-domain within parent somatic ACE. Selective denaturation of C-domain supports the hypothesis of independent folding of the two domains within the ACE molecule. Modeling of ACE secondary structure revealed the difference in predicted structures of the two domains, which, in turn, allowed suggestion of the region 29-133 in amino acid sequence of the N-part of the molecule as responsible for thermostability of the N-domain.     

Efficient construction of a diabody using a refolding system: anti-carcinoembryonic antigen recombinant antibody fragment

Recombinant fragments of the variable region of antibodies are useful in many experimental and clinical applications. However, it can be difficult to obtain these materials in soluble form after their expression in bacteria. Here, we report an efficient procedure for preparing several variable-domain fragments (Fv), single-chain Fv (scFv), and a diabody (the smallest functional bispecific antibody) of anti-carcinoembryonic antigen (CEA) antibody by overexpression in Escherichia coli in inclusion bodies, using a refolding system to obtain renatured proteins. Two types of refolded Fv were prepared: (i) Heavy and light chains of the immunoglobulin variable regions (VH and VL, respectively) were coexpressed with a dicistronic expression vector (designated Fv(co)); (ii) VH and VL were expressed separately, mixed stoichiometrically, and refolded (designated Fv(mix)). All samples refolded with high efficiency; Fv(co), Fv(mix), scFv, and the bispecific diabody bound to several CEA-positive cell lines, exactly as did soluble Fv fragments secreted by E. coli (Fv(sol)) and the parent IgG. The refolded fragments inhibited binding of the parent IgG to CEA-positive cell lines, indicating that their epitope is identical to that of IgG. The bispecific diabody, which combined variable-region fragments of anti-CEA antibody with variable-region fragments of anti-CD3 antibody, was also prepared using the refolding system. This refolded diabody could bind to lymphokine-activated killer cells. In addition, its cytotoxicity toward human bile duct carcinoma TFK-1 and other several other CEA-positive cell lines was concentration-dependent. Taken together, our results suggest that a refolding procedure can be used to prepare various functional antibody fragments (Fv, scFv, and diabody).     

Mutational study on the roles of disulfide bonds in the beta-subunit of gastric H+,K+-ATPase

The gastric proton pump, H(+),K(+)-ATPase, consists of the catalytic alpha-subunit and the non-catalytic beta-subunit. Correct assembly between the alpha- and beta-subunits is essential for the functional expression of H(+),K(+)-ATPase. The beta-subunit contains nine conserved cysteine residues; two are in the cytoplasmic domain, one in the transmembrane domain, and six in the ectodomain. The six cysteine residues in the ectodomain form three disulfide bonds. In this study, we replaced each of the cysteine residues of the beta-subunit with serine individually and in several combinations. The mutant beta-subunits were co-expressed with the alpha-subunit in human embryonic kidney 293 cells, and the role of each cysteine residue or disulfide bond in the alpha/beta assembly, stability, and cell surface delivery of the alpha- and beta-subunits and H(+),K(+)-ATPase activity was studied. Mutant beta-subunits with a replacement of the cytoplasmic and transmembrane cysteines preserved H(+),K(+)-ATPase activity. All the mutant beta-subunits with replacement(s) of the extracellular cysteines did not assemble with the alpha-subunit, resulting in loss of H(+),K(+)-ATPase activity. These mutants did not permit delivery of the alpha-subunit to the cell surface. Therefore, each of these disulfide bonds of the beta-subunit is essential for assembly with the alpha-subunit and expression of H(+),K(+)-ATPase activity as well as for cell surface delivery of the alpha-subunit.     

S-RNases from self-incompatible and -compatible apple cultivars: purification,cloning, enzymic properties,and pollen tube growth inhibitory activity

Four S-RNases (RNase associated with self-incompatibility) were purified from the styles of two apple cultivars (Malus domestica), a self-incompatible cv., Starking Delicious (SD), and a self-compatible cv., Megumi (MG). Each cultivar produced two S-RNases and their enzymatic properties such as specific activity, pH optimum, thermal stability, and molecular mass, were characterized. The four S-RNases inhibited the tube growth of apple pollen in an in vitro bioassay at 25 microg/ml (1.0 microM), but did not distinguish self from non-self pollen. The cDNAs of four S-RNases were cloned, and the nucleotide and deduced amino acid sequences were analyzed. The nucleotide sequence of SD-Se RNase was a new one and the other was identical to that of Sc-RNase of cv. Fuji. In MG one was identical to the sequence of SD-Sc RNase and the other to that of Sa-RNase of cv. Golden Delicious except for one base. From results of the isolation amounts and the Western blot analysis for stylar crude extracts the amount of S-RNases in MG was apparently less than that in SD.     

Subunit protein-affinity isolation of Drosophila DNA polymerase catalytic subunit

gfLittle is known at present about the biochemical properties of very large-sized Drosophila DNA polymerases. In a previous study, we tried to purify Drosophila pol. catalytic subunit from embryos through seven column chromatographies and study its biochemical properties. However, we failed to characterize it precisely because an insufficient amount of the enzyme was generated. In this report, we describe direct purification from Drosophila embryos to near homogeneity using Drosophila DNA polymerase second subunit (Drosophila pol. 2) protein-conjugated affinity column chromatography and characterization of the enzyme in detail. To our knowledge this is the first demonstration of native DNA polymerase purification with activity using a subunit protein-affinity column. We observed new characteristics of Drosophila pol. catalytic subunit as follows: Drosophila pol. catalytic subunit synthesized DNA processively in the presence of both Mn(2+) and Mg(2+) ions, but Mn(2+) inhibited the 3'-5' proofreading activity, thereby decreasing the fidelity of DNA replication by 50%.     

Characterization of murine grancalcin specifically expressed in leukocytes and its possible role in host defense against bacterial infection

Such phagocytic leukocytes as macrophages and neutrophils are the key cellular components of innate immunity. The actin cytoskeleton is essential for their recruitment and activation in infected tissues. We have previously identified p65/L-plastin with Ca(2+)-, calmodulin-, and beta-actin-binding domains in macrophages. In order to further investigate the p65/L-plastin-involved cellular functions, we cloned the cDNA for murine grancalcin, a possible binding partner of p65/L-plastin. According to the sequence, grancalcin is a member of the penta-EF-hand protein family. We prepared recombinant (r) grancalcin for functional studies and found that it exhibited Ca(2+)-dependent precipitation. High-titer antibodies against the protein enabled us to detect intracellular grancalcin. A flow cytometric analysis revealed grancalcin to be highly expressed in macrophages and neutrophils. The protein was particularly abundant in those cells recovered from bacteria-infected sites. Immunohistochemical studies clarified that grancalcin was translocated to the actin cytoskeleton in macrophages upon exposure to bacterial lipopolysaccharide. These findings suggest that grancalcin plays a key role in leukocyte-specific functions that are responsible for host defense.     

Determination of phosphatidylcholine monohydroperoxides using quadrupole time-of-flight mass spectrometry

An improved technique for the analysis of phosphatidylcholine (PC) monohydroperoxides was developed using quadrupole time-of-flight (Q-TOF) mass spectrometry with electrospray ionization. Separation was obtained using an HPLC C8 column with a gradient of methanol and 10 mM aqueous ammonium acetate. Monohydroperoxides of palmitoyl-linoleoyl (C16:0/C18:2) PC, stearoyl-linoleoyl (C18:0/C18:2) PC, and oleoyl-linoleoyl (C18:1/C18:2) PC were detected mainly as MH(+) and [M+Na](+) ions in the heart of the intact rat. Using standard synthetic PCOOH (C16:0/C18:2-OOH), the lipid extract component was identified as (C16:0/C18:2-OOH) PC based on the product ions of ESI-MS-MS and, the PCOOH concentration was quantitated using HPLC with chemiluminescence detection. Two epoxyhydroxy derivatives of the three PCs mentioned above were also detected. This is the first report to show the presence of monohydroperoxides and epoxyhydroxy-derivatives of (C16:0/C18:2)PC, (C18:0/C18:2)PC, and (C18:1/C18:2) PC in the rat heart.