Cell surface oligosaccharide modulation during differentiation. II. Membrane mobility of oligosaccharide lectin conjugates

Cell surface oligosaccharide modulation during differentiation: V. Partial characterization of the regulated surface during substrate adhesion and spreading

In previous studies with IMR-90 human fetal lung fibroblasts, it was shown that modulation of a small finite number of unique cell surface oligosaccharide structural specificities (as defined by reaction with specific lectins and monoclonal antibodies) define the cellular senescence phenotype. The cell surface oligosaccharide display can be characterized by assessing the epitope density and conformational arrangement of three or four individual carbohydrate specificities. Development of the senescence morphological phenotype was preceded by specific alterations in the cell surface oligosaccharide display. The senescence-dependent changes in these displays are primarily related to the binding affinity (the Kij of the Scatchard analyses) rather than the epitope density (the binding capacity, Rij of the Scatchard analyses). These alterations involve rearrangements within specific carbohydrate classes. In the course of these studies, the observation was made that low-density and contact-inhibited growth-retarded Phase II cells showed similar surface modulation of the oligosaccharide display. This suggests a broader significance for the date in growth regulation. These data suggest a structural/functional relationship between cellular senescence mechanisms and growth control in general. In this study we have investigated the possible role of cell surface oligosaccharide regulation in substrate interactions. Trypsinized cells were studied during substrate adherence, spreading and initiation of growth on control and poly-L-ornithine-treated polystyrene substrate. The cell surface oligosaccharide display was characterized using both biological assays and NMR-based measurements of the mobility of water at the cell surface. Results show that trypsinization does not remove or diminish the oligosaccharide display. The initial adherence of the cells to unmodified substrate is mediated by oligosaccharides. Cellular spreading results in specific changes in the display. Initiation of growth corresponds to further specific changes in the display. These data suggest a mechanistic connection between the cell surface oligosaccharide display and growth control of these fibroblasts.

Cell surface oligosaccharide modulation during differentiation: VI. The effect of biomodulation on the senescent and neoplastic cell phenotype

These investigations test the hypothesis developed previously, that there are biomolecules which control and integrate cellular differentiation. Our specific interest in cellular differentiation lies in the area of what we refer to as basal or primitive cellular differentiation mechanisms. These mechanisms are common to all cells, and are required for simple recognition and growth regulation. We have investigated two models, the IMR-90 human fetal lung fibroblast model as a representative of normal growth control, and the CG model, canine glioma cells, a transplantable growth transformed cell line. These two models represent normal, and aberrant cellular differentiation control. In previous studies we have shown that the arrangement of the cell surface oligosaccharide structure on these cell types are predictive of phenotypic transition. We have developed, and partially characterized a series of BIOMODULATORS (BM) which delay the onset of display of neoplastic cells. Three classes of BIOMODULATOR have been explored; (1) a large molecular weight natural product (25-35 kDa), PokeWeed Mitogen (PWM); (2) a small molecular weight natural product (500 Da) Cellular Activator and Differentiator (CAD) and a number of natural and synthetic analogs; and (3) an indolizidine alkaloid natural product, Swainsonine (Sw) which has a known cellular target (oligosaccharide biosynthesis). Preliminary data is presented which structurally links some of these BIOMODULATORS in terms of their effective stereochemistry. These BIOMODULATORS, when used before PDL 38, prevent the cell surface oligosaccharide display changes typical of morphological senescence and delay their onset to PDL 100 or more. These BIOMODULATORS also appear to have regulatory effects on the neoplastic cell models. This re-regulation results in increases in generation time and an increase in the ability of these cells to be recognized by cytotoxic lymphocytes. Proton NMR linewidth measurements of the fraction of 'bound' water associated with the cellular surface of treated and untreated cell populations showed induced physical changes in the cell surface related to the use of the BIOMODULATOR and correlated to the oligosaccharide display changes. These data were interpreted as indicating an increase in the organizational level of these cells. The data for normal and neoplastic cell populations are compared and contrasted in an effort to form the basis for an analytical approach to the control and integration of differentiation mechanisms.

Senescence-induced alteration in cell surface carbohydrates correlated using proton NMR spectroscopy and a lectin-based affinity-binding assay

Changes in the cell surface oligosaccharides in human fetal lung fibroblasts (IMR-90) are studied as the cells progress to senescence using nuclear magnetic resonance spectroscopy (NMR) and a biochemical assay. A lectin-based affinity-binding technique is used which measures the organization of carbohydrates on the cell surface. Proton NMR studies of the water in samples of frozen cell suspensions of young and old cells provide information on the local dynamics of the cell surface by monitoring the motion of bound water. Changes in the lectin binding density and affinity class distribution correlate with a decrease in the water proton linewidth in frozen cells. These observations reflect alterations in the conformation or structure of the cell surface oligosaccharides and local constituent water.

Lectin histochemistry of the embryonic heart: expression of terminal and penultimate galactose residues in developing rats and chicks

Rat embryos at days 10-18 of gestation and chicken embryos at days 3-6 of incubation were fixed and processed for lectin histochemistry. The distribution of binding sites for a lectin from the peanut Arachis hypogaea (PNA) conjugated to horseradish peroxidase (HRP) was determined on tissue sections both before and after enzymatic cleavage of sialic acid with neuraminidase (sialidase). Endocardial cushion tissue in the rat, but not in the chick, reacted with PNA-HRP prior to digestion with sialidase. Endocardium of both species (12 and 13 days in rat, 5 and 6 days in chick), particularly at the level of endocardial cushions, reacted strongly with the sialidase-PNA sequence; this staining decreased markedly after day 14 of gestation in the rat. PNA binding sites capped by sialic acid were most abundant in the developing rat heart during the critical period of endocardial cushion formation and decreased as development proceeded. The marked changes in the appearance and distribution of cardiac cell and tissue glycoconjugates during cardiogenesis support the concept that rapid changes occur in the structure of complex carbohydrates during embryonic and fetal development. The findings also suggest that such glycosylation-related events may be species specific.

Cell surface oligosaccharide modulation during differentiation: IV. Normal and transformed cell growth control

In previous studies it was shown that cell surface oligosaccharide affinity class distributions and binding capacities were down-regulated as normal cells approach senescence. Using a sensitive, amplified, lectin/specific-ligand competition analysis three other growth regulation states were compared to that of cellular senescence. Non-senescent and senescent low-density and contact-induced growth inhibition was compared with neoplastic cell growth control. Non-senescent human fetal lung fibroblasts (IMR-90) down-regulated their mannosyl and galactosyl specificities in response to both low-density and contact-induced growth inhibition. Senescent IMR-90 down-regulate their mannosyl residues in response to contact conditions while they up-regulate their galactosyl residues under the same conditions. Growth-transformed transplantable canine glioma cells did not show density-dependent regulation of their cell surface oligosaccharide structures. Modulation of the CG cells with a specific alpha-mannosidase II inhibitor, Ricinus communis a galactosyl specific lectin, and pokeweed mitogen a cellular differentiating agent resulted in an altered growth phenotype and up-regulation of the mannosyl and galactosyl surface oligosaccharides. These data indicate a controller function for the cell surface oligosaccharides and a general influence on growth control.

Cell surface oligosaccharide modulation during differentiation: III. Lectin affinity class distributions

In previous studies we showed that the onset of the morphological phenotype of cellular senescence (IMR-90) in vitro is preceded by complex cell surface changes. Using fluorescently conjugated lectins these studies showed: (1) quantitative PDL-dependent decreases in cell surface mannosyl, galactosyl, and N-acetyl-glucosamine residues; (2) these changes were correlated with changes in ligand/lectin membrane mobility, suggesting a functional relationship for the quantitative changes. To further investigate the biological significance of these observations we have developed a synthetic ligand competition assay to analyze the lectin binding event itself. The results of these analyses show that: (1) the number of binding affinity class distributions is highly restricted; (2) the PDL-dependent mannosyl change is due to the loss of a high-affinity class distribution without significant change in the low-affinity site; and (3) PDL-dependent changes in both galactosyl and N-acetyl glucosamine binding events are the result of changes in the affinity class distributions. These results are interpreted in terms of the potential available energy to act as the basis for signal transduction at the cell surface.

Membrane oligosaccharides: structure and function during differentiation

Recent results gathered by normal light microscopy, immunocytochemistry, fluorescent-analog cytochemistry, and electron microscopy have allowed an improved interpretation of ameboid movement and related phenomena. 1. The contractile system responsible in Amoeba proteus for the generation of motive force for protoplasmic streaming and a large variety of dynamic activities is represented mainly by a thin cortical filament layer at the cytoplasmic face of the cell membrane (Fig. 18I). During normal locomotion this layer exhibits a distinct structural and physiological polarity with three different zones: a zone of reformation at the front (A), a zone of contraction in the intermediate cell region (B), and a zone of destruction at the uroid (C). 2. Two types of filaments participate in the formation of the cortical layer: (1) randomly distributed thin (actin) filaments exhibiting a parallel orientation in the anterior (Fc1) and a disordered arrangement in the intermediate and posterior cell region (Fc2; see also Fig. 17b), and (2) thick (myosin) filaments in close association with F-actin and mostly restricted to the intermediate and posterior cell region (Fc2). 3. The internal hydraulic pressure generated by localized active contraction of the cortical layer is transmitted to the endoplasm via the cell membrane and converted into directed streaming by a gel-sol gradient of decreasing viscosity between the uroid and the front. Calcium ions, ATP, and regulative proteins (profilin and a kinase) play an essential role in controlling both the interaction of actin and myosin and the sol-gel state of the cytoplasmic matrix. 4. Any alterations externally induced in the polarity of the cortical filament system by chemical or physical stimulation and inhibition cause immobilization of the amebas (Fig. 18II) with characteristic changes in (1) cell shape (spherulation and cell flattening), (2) membrane dynamics (cytotic and cytokinetic activities), and (3) cytoplasmic organization (hyalogranuloplasmic separation). pseudopodial tip (Fig. 18III, b----c, d----e), (3) destruction of the old layer at the hyalogranuloplasmic border (Fig. 18III, c,e), and (4) alternate solation (Fig. 18III, b and d) and gelation (Fig. 18III, c and e) of the hyaloplasm between the layer and the plasma membrane. The retraction of pseudopodia is accomplished by a local contraction of the cortical layer in conjunction with a simultaneous gel-sol transformation of the ectoplasmic cylinder. 6. The expression of a rather complex cytoskeleton which is composed not only of microfilaments and associated proteins, but also of intermediate- and microtubularlike structures has to be considered in future