Delivery of liposome-sequestered hydrophobic proteins to lysosomes of normal and Batten disease cells

We have developed a method to deliver hydrophobic proteins such as ATP synthase subunit c and ubiquitin to lysosomes of PMN (polymorphonucleocytes) and fibroblasts. ATP synthase subunit c is stored in the lysosomes of various tissues in late infantile and juvenile forms of neuronal ceriod lipofuscinosis, also called Batten disease (BD). Whether this protein storage is due to an abbreviation in protein or in the lysosomal hydrolases of BD is still not clear. We have sequestered this protein and ubiquitin in the lipid membrane of liposomes. The liposomes coated with autologous heat-aggregated IgG or apolipoprotein E when presented to the PMN and fibroblasts, respectively, accumulated in the lysosomes. Both normal and BD PMN degraded 125I-ubiquitin; the rate of degradation was, however, slower by Batten PMN. These studies indicate that a hydrophobic molecule such as subunit c can be delivered to PMN and fibroblasts, and the sequestered proteins are accessible to lysosomal hydrolases. Therefore, this technique can be used to study the metabolism of highly hydrophobic proteins by lysosomes, especially the biochemical mechanism(s) of subunit c storage in BD.

Sequential excision of internal eliminated DNA sequences in the differentiating macronucleus of the hypotrichous ciliate Stylonychia lemnae

Elimination of internal eliminated sequences (IES) during macronuclear development of the hypotrichous ciliate Stylonychia lemnae was analyzed in one cluster of macronuclear precursor DNA sequences. The results indicate that IES elimination is a highly ordered process, it starts very early during macronuclear development and has only finished immediately before DNA fragmentation takes place. It occurs in distinct steps and the IES are eliminated in a specific order, where a defined IES is only removed after complete elimination of other IES. Transfection experiments clearly demonstrate that the structure of the IES itself is not sufficient for its correct excision but other cis-acting sequences or additional structural requirements are needed for IES elimination.

Murine alpha-macroglobulins demonstrate divergent activities as neutralizers of transforming growth factor-beta and as inducers of nitric oxide synthesis. A possible mechanism for the endotoxin insensitivity of the alpha2-macroglobulin gene knock-out mouse

alpha2-Macroglobulin null mice demonstrate increased resistance to endotoxin challenge (Umans, L., Serneels, L., Overbergh, L., Van Leuven, F., and Van den Berghe, H. (1995) J. Biol. Chem. 270, 19778-19785). We hypothesized that this phenotype might reflect the function of murine alpha2M (malpha2M) as a neutralizer of transforming growth factor-beta (TGF-beta) and inducer of nitric oxide synthesis in vivo. When incubated with wild-type mouse plasma, TGF-beta1 and TGF-beta2 bound only to malpha2M. Alternative TGF-beta-binding proteins were not detected in plasma from alpha2M(-/-) mice. Wild-type mouse plasma, but not plasma from alpha2M(-/-) mice, inhibited TGF-beta1 binding to TGF-beta receptors on fibroblasts. Purified malpha2M bound TGF-beta1 and TGF-beta2 with similar affinity; the KD values were 28 +/- 4 and 33 +/- 4 nM, respectively. Murinoglobulin, the second murine alpha-macroglobulin, bound both TGF-beta isoforms with 30-fold lower affinity. Malpha2M counteracted the activities of TGF-beta1 and TGF-beta2 in an endothelial cell growth assay. Malpha2M also induced NO synthesis when incubated with RAW 264.7 cells, an activity which probably results from the neutralization of autocrine TGF-beta activity. Human alpha2M induced NO synthesis comparably to malpha2M; however, MUG had no effect. These studies demonstrate that the ability to neutralize TGF-beta is a property of malpha2M, which is not redundant in the murine alpha-macroglobulin family or in murine plasma. Malpha2M is the only murine alpha-macroglobulin that promotes NO synthesis. The absence of malpha2M, in alpha2M(-/-) mice, may allow TGF-beta to more efficiently suppress excessive iNOS expression following endotoxin challenge.

Phylogeny and biogeography of Panax L. (the ginseng genus, araliaceae): inferences from ITS sequences of nuclear ribosomal DNA

Panax, the ginseng genus, is one of the most medicinally important genera in the Orient and demonstrates a classical eastern Asian and eastern North American disjunct distributional pattern. Sequences of the internal transcribed spacers (ITS) and the 5.8S coding region of the nuclear ribosomal DNA repeat were obtained for the 12 species of Panax to reconstruct phylogenetic relationships. Of the 2 eastern North American species, P. quinquefolius and P. trifolius, P. quinquefolius was suggested to be more closely related to the eastern Asian species in the ITS tree, while P. trifolius was phylogenetically isolated. Monophyly of the three medicinally most important species, P. ginseng, P. notoginseng, and P. quinquefolius, suggested by previous workers, was not supported by the ITS data. A close phylogenetic relationship between Panax and Aralia was supported. Several biogeographical implications were inferred: (1) two divergence events have produced the eastern Asian and eastern North American disjunct distribution in Panax, (2) no intercontinental species pairs are found in Panax; (3) a discrepancy between the sequence divergence pattern and the phylogenetic pattern was observed in Panax, suggesting the need for caution in using sequence divergence data alone in inferring biogeographical patterns; (4) the Himalayas and central and western China are the current centers of diversity of the ginseng genus; and (5) the low ITS sequence divergence and a close relationship among species in that region suggest that rapid evolutionary radiation may have created such a diversity of Panax in the Himalayas and in central and western China.

Human hepatic lipase subunit structure determination

Chinese hamster ovary cells were stably transfected with a human hepatic lipase (HL) cDNA. The recombinant enzyme was purified from culture medium in milligram quantities and shown to have a molecular weight, specific activity, and heparin affinity equivalent to HL present in human post-heparin plasma. The techniques of intensity light scattering, sedimentation equilibrium, and radiation inactivation were employed to assess the subunit structure of HL. For intensity light scattering, purified enzyme was subjected to size exclusion chromatography coupled to three detectors in series: an ultraviolet absorbance monitor, a differential refractometer, and a light scattering photometer. The polypeptide molecular weight (without carbohydrate contributions) was calculated using the measurements from the three detectors combined with the extinction coefficient of human HL. A single protein peak containing HL activity was identified and calculated to have a molecular mass of 107,000 in excellent agreement with the expected value for a dimer of HL (106.8 kDa). In addition, sedimentation equilibrium studies revealed that HL had a molecular mass (with carbohydrate contributions) of 121 kDa. Finally, to determine the smallest structural unit required for lipolytic activity, HL was subjected to radiation inactivation. Purified HL was exposed to various doses of high energy electrons at -135 degrees C; lipase activity decreased as a single exponential function of the radiation dose to less than 0.01% remaining activity. The target size of functional HL was calculated to be 109 kDa, whereas the size of the structural unit was determined to be 63 kDa. These data indicate that two HL monomer subunits are required for lipolytic activity, consistent with an HL homodimer. A model for active dimeric hepatic lipase is presented with implications for physiological function.

Size-exclusion chromatography with on-line light-scattering, absorbance, and refractive index detectors for studying proteins and their interactions

Techniques of using size-exclusion chromatography (SEC) with on-line light-scattering, uv absorbance, and refractive index detectors to characterize the polypeptide molecular weights of simple proteins or glycoproteins or to determine the stoichiometry of protein complexes are described. Two unique advantages of this approach over conventional SEC are that the molecular weight measurement is independent of elution position and can exclude the contributions from carbohydrates. When a protein or complex contains no carbohydrates, a two-detector method, i.e., light scattering combined with refractive index, can be used to calculate the molecular weight. When a protein contains carbohydrates, a three-detector method is used to calculate the molecular weight of polypeptide alone. Finally, a self-consistent three-detector method is used to determine the stoichiometry of a protein complex containing carbohydrates. Example applications for all these methodologies are described.

ErbB receptor activation, cell morphology changes, and apoptosis induced by anti-Her2 monoclonal antibodies

A panel of mAbs were generated against the purified soluble form of erbB2/Her2 receptor, corresponding to the extracellular region of the receptor, and examined for their ability to mimic the receptor ligand. Some of the mAbs strongly induced tyrosine phosphorylation of 180-185 kDa proteins, including not only Her2 but also Her3 and Her4 receptors, when they were expressed on the surface of breast cancer cells. These mAbs do not cross-react with Her3 or Her4 as demonstrated by competition study. Receptor phosphorylation was also observed with the cell lines transfected with Her2 or a chimeric receptor consisting of the extracellular domain of Her2 and the transmembrane and cytoplasmic domains of epidermal growth factor receptor. Selected mAbs were tested for their ability to change cell morphology, and one specific mAb, mAb74, induced cell morphology changes and apoptosis.

Oxidative stability and alpha-tocopherol retention in turkey burgers during refrigerated and frozen storage as influenced by dietary alpha-tocopheryl acetate

1. The effect of vitamin E (alpha-tocopheryl acetate) in turkey diets on the oxidative stability of raw and cooked turkey burgers and on the retention of alpha-tocopherol during refrigerated (4 degrees C) or frozen (-20 degrees C) storage was investigated. One hundred and two, one-day-old T-8s turkey poults were divided at random into 3 groups of 34 animals each and fed on either a basal diet (normal commercial turkey diet) supplemented with 20 mg alpha-tocopheryl acetate/kg (control) or fed an alpha-tocopherol supplemented diet containing 300 (E300) or 600 (E600) mg alpha-tocopheryl acetate/kg for 21 weeks. 2. Dietary supplementation with alpha-tocopheryl acetate significantly reduced TBARS numbers in both raw and cooked burgers during refrigerated and frozen storage. 3. The mean values of alpha-tocopherol in raw and cooked burgers stored at 4 degrees C did not change during storage. 4. In the case of both raw and cooked samples stored at -20 degrees C, the alpha-tocopherol values decreased from 5.67 to 3.54 and from 3.56 to 2.30 micrograms/g in the raw burgers from turkeys from the E600 and E300 treatments, respectively, after 4 months storage. The values decreased from 5.60 to 2.88 and from 3.29 to 1.85 micrograms/g in cooked burgers from turkeys from the E600 and E300 treatments, respectively, after 5 months storage.

Characterization of keratinocyte growth factor binding to heparin and dextran sulfate

Binding of keratinocyte growth factor (KGF) with heparin (molecular weight of 5000) and dextran sulfate (molecular weight of 8000) was studied using an online monitoring of size-exclusion chromatography with light scattering, refractive index, and uv absorbance detectors. This technique allows the determination of the molecular weight of KGF eluting as complexes with the above polymers. When mixtures of KGF with heparin were injected into the column, two peaks of heparin/KGF complexes were observed. The first peak corresponded to, on average, 3.4 KGF per complex and the second peak to an average of about 2 KGF per complex. These results suggest that the heparin/ KGF complex is heterogeneous, consisting of 1,2,3, and 4 KGF molecules per complex. To calculate the number of heparin molecules in these complexes, the rate of disappearance of free KGF was determined as heparin was added. The average number of KGF bound to 1 mol of heparin was calculated to be about 2 mol, suggesting that only one heparin molecule is present in these complexes. The heparin binding of two KGF mutants, i.e., (C1, 15S)KGF (with substitutions of serine for cysteines 1 and 15) and d28KGF (lacking 28 N-terminal amino acid residues), was essentially identical to that of the native sequence KGF. A similar experiment was carried out for KGF binding to dextran sulfate. The molecular weight of the complex corresponded to 2 to 2.6 KGF molecules per complex. The rate of disappearance of free KGF as the dextran sulfate added showed 2-3 mol of KGF bound to 1 mol of dextran sulfate, consistent with the idea that the complex contains only 1 dextran sulfate molecule.

Inguinal lymph node foreign body granulomas after placement of a silicone rubber (Silflex) implant of the first metatarsophalangeal joint

We describe a woman who developed foreign body granulomas 8 years after metatarsophalangeal (MTP) joint silicone rubber implantation for hallux rigidus. She developed overnight swelling and tenderness in the inguinal region on the ipsilateral side. Histological evaluation of the lymph node showed foreign body granulomas. Electron microscopy and dispersion x-ray analysis identified the foreign body material in the inguinal lymph node and fibrous capsule surrounding the implant as silicone. Foreign body granulomas of surrounding tissues and regional lymph nodes are infrequently reported postoperative complications in patients with small joint silicone rubber implants. A fractured or eroded implant surface attributed to wear is usually noted at prosthesis excision. Granulomas in normal or enlarged lymph nodes have been described in both symptomatic and asymptomatic patients, with intact or fractured prostheses. Many related joint and lymph node symptoms resolve with removal of the silicone rubber prosthesis.

Complete sequence, subunit structure, and complexes with pancreatic alpha-amylase of an alpha-amylase inhibitor from Phaseolus vulgaris white kidney beans

The complete amino acid sequence of a white kidney bean (Phaseolus vulgaris) alpha-amylase inhibitor (PHA-I), which is composed of two kinds of glycopolypeptide subunits, alpha and beta, was established by conventional methods. The polypeptide molecular weight of PHA-I determined by the light-scattering technique, considered together with the sequence molecular weights revealed for the subunits, indicated that PHA-I has the subunit stoichiometry of (alpha beta)2 complex. Inhibition test of PHA-I with increasing amounts of porcine pancreatic alpha-amylase (PPA) suggested that an inactive 2:1 complex is formed between PPA and PHA-I. In fact, two complexes differing from each other in the molar ratio of PPA to PHA-I were separated by gel filtration, and molecular weight estimation by the light-scattering technique confirmed that they are complexes of PHA-I with one or two PPA molecules. The binding of PPA to PHA-I appeared to follow simple binomial statistics, suggesting that two binding sites on PHA-I are independent and of high affinity for PPA.

Pulmonary malakoplakia in acquired immunodeficiency syndrome: an ultrastructural study of morphogenesis of Michaelis-Gutmann bodies

Malakoplakia is an unusual inflammatory reaction to a variety of infections, characterized by the accumulation of macrophages containing the target-like calcospherites, the Michaelis-Gutmann body (MGB). We report three patients with acquired immunodeficiency syndrome with pulmonary malakoplakia associated with Rhodococcus equi infection; two patients were diagnosed at autopsy and one by examination of a transbronchial biopsy specimen. All three patients had pulmonary bacterial cultures and light and electron microscopic examination. The patients were 33-, 41-, and 43-year old men, human immunodeficiency virus-positive for 2, 6, 8 years, respectively. The two patients diagnosed at autopsy had cavitary lesions, and the patient diagnosed by biopsy specimen had nodular lesions on chest radiographs. Histologically, the lungs had well-circumscribed areas of infiltration with benign macrophages with granular cytoplasm, scattered MGBs, and numerous gram-positive coccobacilli. Electron microscopic examination showed intracellular coccobacilli, from 990 X 702 to 972 X 648 nm in diameter, with thick, homogenous cell walls, trilaminar cytoplasmic membranes, and dense cytoplasm with from one to five vacuoles. Electron microscopic studies showed that the bacteria within the pulmonary macrophages had thicker cell walls, less prominent nucleoid areas, and more vacuoles than the bacteria in cultures from the sputum and blood. The mature MGB ultrastructurally had a concentric, trilaminate structure with central mineralized core and was without recognizable bacterial forms. Early MGBs, however, consisted of a circular, electron-dense core containing bacteria, ultrastructurally similar to the R. equi seen in the culture. Pulmonary malakoplakia in patients with the acquired immunodeficiency syndrome might thus represent an acquired macrophage dysfunction of the intracellular digestion of phagocytized bacteria. The bacteria within the macrophages, however, seemed to have thicker cell walls compared with those in culture, and thus might be protected from enzyme digestion. It seems that MGBs are formed around the undigested bacteria as an alternative pathway for bacterial destruction, because R. equi was identified within the cores of early MGBs but not the mature or late stage MGBs.

Dimerization of the extracellular domain of granuloycte-colony stimulating factor receptor by ligand binding: a monovalent ligand induces 2:2 complexes

Granulocyte-colony stimulating factor (G-CSF) binds to a specific cell surface receptor and induces signals for growth and differentiation in cells of granulocyte hematopoietic lineage. In order to understand how G-CSF binding initiates signals into these cells, we have studied its interactions with the entire extracellular domain of the receptor (sG-CSFR). The sG-CSFR was purified from CHO cell conditioned media with a G-CSF affinity column, resting in a preparation fully competent for ligand binding. However, when sG-CSFR was purified by conventional means, i.e., without affinity chromatography, only about half was competent. Therefore, all studies were carried out using affinity-purified material. The sG-CSFR exhibited a weak self-association into a dimer with a dissociation constant of 200microM in the absence of G-CSF. Addition of G-CSF dimerizes the receptor, with a preferred stoichiometry of 2 G-CSF molecules plus 2 receptors. Unexpectedly, receptor-receptor interactions rather than through two receptors binding to the same G-CSF molecule; i.e., G-CSF is a monovalent ligand. G-CSF binding to the receptor monomer occurs with high affinity. The binding of G-CSF also enhances the receptor-receptor dimerization; when G-CSF is bound to both receptors, dimerization is enhanced 2000-fold, while the interaction of a 1:1 receptor-ligand complex with a second ligand-free receptor is enhanced 80-fold. Thus, the mechanism of receptor dimerization is fundamentally different than that of related cytokine receptors such as growth hormone and erythropoietin receptors. Circular dichroic spectra showed a small but significant conformational change of receptor upon binding G-CSF. This is consistent with the idea that G-CSF binding alters the conformation of the receptor, resulting in an increase in receptor-receptor interactions.

Human stem cell factor dimer forms a complex with two molecules of the extracellular domain of its receptor, Kit

Stem cell factor (SCF) is a cytokine that is active toward hematopoietic progenitor cells and other cell types, including germ cells, melanocytes, and mast cells, which express its receptor, the tyrosine kinase, Kit. SCF exists as noncovalently associated dimer at concentrations where it has been possible to study its quaternary structure; it stimulates dimerization and autophosphorylation of Kit at the cell surface. We have used recombinant versions of human SCF and human Kit extracellular domain (sKit) to study SCF-Kit interactions. By size exclusion chromatography, plus various physical chemical methods including light scattering, sedimentation equilibrium, and titration calorimetry, we demonstrate the formation of complexes containing a dimer of SCF (unglycosylated SCF1-165) plus two molecules of sKit. The concentrations of SCF and sKit in these studies were in the range of 0.35-16.2 microM. The data are analyzed and discussed in the context of several possible models for complex formation. In particular, the sedimentation data are not consistent with a model involving cooperative binding. The Kd estimate for SCF-sKit interaction, obtained by sedimentation equilibrium, is about 17 nm at 25 degrees C. With glycosylated SCF1-165, the Kd is considerably higher.

Isolation of anti-leukemia compounds from Citrus reticulata

In vitro effects of medicinal plant extracts from the pericarpium of Citrus reticulata (cv Jiao Gan) (PCRJ) on the growth and differentiation of a recently characterized murine myeloid leukemic cell clone WEHI 3B (JCS) were investigated. Extracts of PCRJ not only inhibited the proliferation of JCS cells in a dose dependent manner, but also induced differentiation of JCS cells into macrophages and granulocytes. Morphological differentiation of PCRJ treated JCS cells was associated with an increase in phagocytic activity of the cells. Furthermore, both in vitro clonogenicity and in vivo growth of PCRJ treated JCS leukemic cells in syngeneic BALB/c mice were significantly reduced. The survival rate of mice receiving PCRJ treated JCS tumour cells was also increased. Using 1H-NMR, 13C-NMR, and GC/MS, two active components isolated from PCRJ were identified as nobiletin and tangeretin.

Dimerization of the extracellular domain of the erythropoietin (EPO) receptor by EPO: one high-affinity and one low-affinity interaction

Although there is considerable evidence that signaling by the erythropoietin (EPO) receptor is initiated when it is dimerized by binding EPO, it has been previously reported that the soluble extracellular domains of the EPO receptor (sEPOR) are not dimerized in the presence of EPO and are able to form only 1:1 complexes with EPO. We have now shown unambiguously by light scattering, sedimentation equilibrium, and titration calorimetry that two molecules of sEPOR can bind to a single EPO monomer but that the binding of the second sEPOR is approximately 1000-fold weaker than that of the first. Because this second binding interaction is quite weak (Kd of approximately 1 microM), the 2:1 sEPOR.EPO complexes are easily dissociated during chromatography (forming the 1:1 complexes reported previously) and cannot be isolated in pure form. Global analysis of the sedimentation equilibrium data has enabled us to determine the binding constants and is consistent with a model in which EPO has two independent binding sites for sEPOR but cannot exclude anticooperative or sequential binding models. The influence of glycosylation of EPO and/or sEPOR on the binding affinities has also been investigated. Titration calorimetry is consistent with the sedimentation data and shows that the weaker binding site has a more negative delta H. The relation of these results to the binding of EPO to membrane-bound receptors and to the phenomenon of apparent high-affinity and low-affinity classes of receptors is discussed.

Exploring the allowed sequence space of a membrane protein

We present a comprehensive view of the tolerance of a membrane protein to sequence substitution. We find that the protein, diacylglycerol kinase from Escherichia coli, is extremely tolerant to sequence changes with three-quarters of the residues tolerating non-conservative changes. The conserved residues are distributed with approximately the same frequency in the soluble and transmembrane portions of the protein, but the most critical active-site residues appear to residue in the second cytoplasmic domain. It is remarkable that a unique structure of the membrane embedded portion of the protein can be encoded by a sequence that is so tolerant to substitution.

Absorption by 1-year-old children of an iron supplement given with cow's milk or juice

A paucity of data are available on toddlers for the evaluation of optimal strategies of Fe supplementation. In this study, we used a two-tracer stable isotope technique to determine Fe absorption from a 5-mg dose of stable isotopically enriched (57Fe or 58Fe) ferrous sulfate given with cow's milk (CM) compared with the same dose given with apple juice. Ten children (age 13 +/- 1 mo, weight 10.8 +/- 1.1 kg) who had recently discontinued formula feeding and begun on CM were studied. Red blood cell (RBC) iron incorporation of the isotope was determined 14 d after dosing with 57Fe and 58Fe. Fe absorption was calculated based on the assumption that 90% of absorbed Fe is incorporated into RBC. Absorption of Fe was significantly greater (13.7 +/- 6.4%) when given with juice than with milk (5.7 +/- 4.0%), p < 0.01 by paired t tests. Fe absorption from the dose given with juice was significantly negatively correlated with serum ferritin (n = 9, r = -0.70, p < 0.05). These results indicate that 1) a small supplement of Fe is better absorbed when given with juice than with CM, and 2) a large variability in Fe absorption exists in healthy 1-y-old infants, which is related to their existing Fe stores.

A patient-derived cytotoxic T-lymphocyte clone and two peptide-dependent monoclonal antibodies recognize HLA-B27-peptide complexes with low stringency for peptide sequences

HLA-B27 molecules expressed on the T2 mutant cell line do not have peptides. Such empty HLA-B27 molecules were not recognized by an HLA-B27-restricted cytotoxic T-lymphocyte (CTL) clone (auto-1) derived from synovial fluid. To test for peptide dependency of the clone, B27-T2 cells were incubated with a panel of 48 different peptides. This lack of stringency was compared with that of a peptide-dependent monoclonal antibody, B27.M2. Positive B27.M2 reactivity resulted when the B27-T2 cells were incubated with two peptides: RRKAMFEDI and RRMGPPVGHR, derived from Chlamydia HSP60 and human ribonucleoprotein, respectively. Because of the limited availability of CTL versus monoclonal antibody, the specificity of B27.M2 was studied in greater detail. The importance of the HLA-B27 heavy chain in antibody recognition of class I-peptide complexes was demonstrated by site-directed mutagenesis. The stringency of the peptide residues was tested by making analogs of each of the nine residues in RRKAMFEDI, creating a panel of 180 analogs. Although stringency was highest for the sixth position, as many as six different amino acids provided positive reactivity. These results indicate that immune recognition of HLA-B27-peptide complexes might have rather low stringency for the peptide sequences. In theory, then, pathogen-derived peptides which induce autoimmunity by generating autoreactive CTL might not share much sequence similarity with the responsible self peptides.

PYY and GLP-1 contribute to feedback inhibition from the canine ileum and colon

To explore mechanisms whereby unabsorbed nutrients in the ileum inhibit the upper gut ("ileal brake"), we perfused the canine ileum or colon and monitored phase 3 in the duodenum. Fasting motility was recorded when the ileum or colon was perfused with 154 mM NaCl, a mixed isotonic nutrient solution (Ensure), or individual nutrients (maltose, casein hydrolysates, or sodium oleate). Blood samples were collected before and during the perfusions. The ileum was also perfused with 154 mM NaCl while peptide YY (PYY) was infused by vein. In both sets of experiments, plasma levels of PYY, neurotensin, and glucagon-like peptide-1 (GLP-1) were measured. Ileal or colonic perfusion of Ensure delayed phase 3 [migrating motor complexes (MMC)] in the duodenum, inhibited ileal motility, and increased plasma levels of PYY and GLP-1. Ileal casein and oleate and colonic casein also delayed the duodenal MMC. The MMC cycle length and plasma levels of PYY were closely correlated. Intravenous PYY prolonged the MMC cycle; an intravenous dose of 100 pmol.kg-1.h-1 of PYY mimicked the effects of ileal Ensure. These results support the hypothesis that PYY, and possibly GLP-1, participate in the ileal brake. This negative feedback loop also affects the distal small bowel. The proximal colon also triggers the feedback inhibition of gut motility (colonic brake).

Binding of Neu differentiation factor with the extracellular domain of Her2 and Her3

The interaction of neu differentiation factor (NDF) with the extracellular domains of Her2 (sHer2) and Her3 (sHer3) have been studied using native gels, light scattering, and sedimentation equilibrium. The full-length NDF beta 2 was shown to bind sHer3 with a dissociation constant of 26 +/- 9 nM, while it showed a 1000-fold weaker binding to sHer2. Taken together, these results demonstrate that NDF is a high affinity ligand for Her3, but not for Her2. No increase in affinity of the NDF beta 2 for sHer3 was observed upon addition of sHer2 to the NDF beta 2-sHer3 mixture. Binding of NDF beta 2 to sHer3 did not induce receptor dimerization or oligomerization, the stoichiometry being one sHer3 per one NDF molecule. This finding suggests that transmembrane and/or intracellular domains of receptor family members or perhaps additional unidentified components may be involved in NDF induced dimerization and autophosphorylation, or alternatively, that dimerization is not the mechanism for Her3 autophosphorylation and signal transduction.

A new strategy for enhancing the stability of lyophilized protein: the effect of the reconstitution medium on keratinocyte growth factor

PURPOSE

Protein stabilization during lyophilization has previously focused on optimization of the formulation as well as the freezing and dehydration process parameters. However, the effect of the reconstitution medium has been largely neglected. We have investigated its effect on aggregate formation using recombinant keratinocyte growth factor (KGF).

METHODS

The protein was lyophilized under suboptimal conditions to induce aggregation and precipitation upon reconstitution with water. A series of additives were examined by UV spectrophotometry and size exclusion chromatography (SEC-HPLC) for their effects on decreasing the degree of KGF aggregation and precipitation by the increase in recovery of soluble monomer.

RESULTS

Several additives resulted in a significant reduction of aggregation, including sulfated polysaccharides, surfactants, polyphosphates, and amino acids. A similar effect was achieved by adjusting the ionic strength of the reconstitution medium. SEC-HPLC indicated that the amount of soluble monomer was also increased by these additives suggesting that the recovery of the soluble protein correlates with the native, monomeric protein.

CONCLUSIONS

These results suggest that optimization of reconstitution conditions will be a useful methodology for increasing the recovery of soluble, active proteins and that for KGF, the recovery of the soluble protein correlates with the native, monomeric form.