Differences in the redistribution of concanavalin A and wheat germ agglutinin binding sites on mouse neuroblastoma cells

A review of reagents for fluorescence microscopy of cellular compartments and structures, Part III: reagents for actin, tubulin, cellular membranes, and whole cell and cytoplasm

Non-antibody commercial fluorescent reagents for imaging of cytoskeletal structures have been limited primarily to tubulin and actin, with the main factor in choice based mainly on whether cells are live or fixed and permeabilized. A wider range of options exist for cell membrane dyes, and the choice of reagent primarily depends on the preferred localization in the cell (i.e., all membranes or only the plasma membrane) and usage (i.e., whether the protocol involves fixation and permeabilization). For whole-cell or cytoplasmic imaging, the choice of reagent is determined mostly by the length of time that the cells need to be visualized (hours or days) and by fixation status. Presented here is a discussion on choosing commercially available reagents for these cellular structures, with an emphasis on use for microscopic imaging, with a featured reagent for each structure, a recommended protocol, troubleshooting guide, and example image.

Transmembrane cytoskeletal modulation in preterminal growing axons. II. Limax flavus agglutinin-induced receptor redistribution, capping and internalization in varicosities of growing axons

Growing retinal ganglion cell axons of the goldfish exhibit varicosities of varying sizes and smaller non-protruding phase-dense inclusions that are mobile and mediate rapid bulk redistribution of axoplasm. In fixed axons, Limax flavus agglutinin, a lectin specific for sialic acid which has been shown to inhibit organelle transport in these axons, preferentially labels surface membrane associated with varicosities and inclusions in preterminal axons. In viable axons, Limax flavus agglutinin causes: (1) agglutination of closely apposed axons, (2) redistribution of lectin-binding sites on varicosities to surfaces of interaxonal contact with other varicosities, forming 'fused' multivaricosity complexes, and (3) formation of vacuoles in many single varicosities and some multivaricosity complexes. Vacuoles contain Limax flavus agglutinin binding sites distributed circumferentially. On the basis of immunocytochemistry, actin, myosin, calmodulin and alpha-spectrin are co-localized with redistributed Limax flavus agglutinin binding sites. The agglutination, redistribution of lectin binding sites and changes in the cytoskeleton can be reversed by treatment with sialic acid. The lectin-induced vacuole formation and internalization of Limax flavus agglutinin receptors can also be blocked either by sodium azide in a glucose-free medium, or by pretreatment with cytochalasin D and indicate an energy and a cytoskeletal dependence. The Limax flavus agglutinin-induced structural rearrangements are not altered after limited digestion with pronase. Western blots after ultramicroelectrophoresis of retinal ganglion cell axons subjected to limited digestion reveal Limax flavus agglutinin labelling of bands with apparent Mr of 64 and 70 KDa. In undigested axons, some 70 KDa protein remains unextracted with Triton X-100 lysis of axonal fields, and more remains unextracted when axonal fields are pretreated with Limax flavus agglutinin before Triton lysis, suggesting increased association with the cytoskeleton in response to lectin binding. The results indicate that cross-linking of one or more sialoglycoconjugates on the surface of varicosities of preterminal growing retinal ganglion cell axons causes a constellation of transmembrane-mediated cytoskeletal and membrane changes that are akin to those described for capping in motile cells.

Ultrastructural localization of calcium binding sites on human muscle cell surface

Calcium (Ca2+) is mainly bound to anionic phospholipids and to sialic acid at the cell surface. We studied the ultrastructural localization of these Ca2+ binding sites in normal human muscle fibers, using Polymyxin B as a marker for anionic phospholipids and the lectin Limulus Polyphemus as a probe for sialic acid. We found that anionic phospholipids have a patchy distribution along the muscle sarcolemma, with a preferential localization at the I band level and at the junction between the I and A band. Sialic acid has an uniform distribution along the muscle plasma membrane and basal lamina. Our observations suggest that the plasma membrane, basal lamina, and transverse tubular system play an important role in providing the negative charge of the human muscle cell surface and that these structures may be involved in the binding of calcium.

The use of fluorochromes in the cytochemical characterization of some phytoflagellates

Sixteen fluorochromes were tested for the cytochemical characterization of two dinoflagellates (Amphidinuim carterae, Prorocentrum micans) and one chlorophycean flagellate (Dunaliella tertiolecta). Depending on the fluorochrome used, various cellular components (including the plasma membrane, thecal plates, pusule, trichocysts, nucleus, lipid bodies and vacuoles) were revealed. The different colours obtained from single or double fluorochrome staining enabled the differentiation and identification of most cellular components. Protoplasmic staining with Fluorescein diacetate suggested the occurrence of esterases in the three phytoflagellates. Rhodamine B, Neutral Red, FluoroBora P and Nile Blue revealed extensive occurrence of lipoid bodies in A. carterae, but Nile Blue showed considerable difference from the other stains in the inclusion size and intracellular location of these bodies. Chlortetracycline binding, and its inhibition by the Ca2+ionophore A23187, indicated that the plasma membrane, pusule system and trichocysts contain sites of Ca2+ binding. Calcofluor White ST proved superior to Congo Red and Lucifer Yellow in elucidating structural details of the thecal plates of P. micans. While Acridine Orange revealed the presence of surface-coat acidic polysaccharides, the fluoresceinated lectins established their glycoconjugate nature in all the three flagellates. Possible mechanisms of fluorochrome uptake are discussed.

Electron cytochemical study of the muscle cell surface

The lectins wheat germ agglutinin and limulus polyphemus were used as cytochemical probes to study the ultrastructural localization of sialic acid at the cell surface of rat muscle fibers. In addition cytochemical studies employing strontium as an electron-dense marker were also carried out to investigate cation binding sites at the muscle cell surface. The results showed binding of the lectins to the glycocalyx, caveolae and the basal lamina of the muscle fibers. These binding sites matched the ones observed in the cytochemical studies using strontium as a marker. Based on these observations we suggest that the glycocalyx, caveolae and the basal lamina of the muscle fiber may be involved in the binding of Ca++ and that significant amounts of Ca++ may be normally present at the muscle cell surface.

A comparative study of the intracellular lectin binding sites of neurons in culture with neurons in situ

The cytochemical properties of intracellular membrane systems which are likely to be subcellular sites of glycoprotein oligosaccharide synthesis and trafficking have been compared in cultured neuroblastoma cells (as a potential model system) and in Purkinje neurons of rat cerebellum. In aldehyde-fixed N18 cells, permeabilized with Triton X-100, concanavalin A (Con A) binding sites were found in the somata, neurites, and growth cones. Con A binding sites in growth cones appeared as a fine, membranous network. Wheat germ agglutinin (WGA) binding sites were restricted to the perinuclear region of the soma and to the distal tips of growing neurites. As shown previously, Purkinje cell somata and presynaptic terminals also contain Con A binding sites. In this study, WGA and succinylated WGA binding sites were observed in the presynaptic terminals of Purkinje cells. Neuraminidase enzyme digestion prior to lectin labeling removed or greatly reduced WGA binding in the neuropil of the deep nucleus but not in presynaptic terminals of Purkinje cells. Succinylated WGA binding sites were not affected by neuraminidase digestion. Neuraminidase digestion also exposed Ricinis communis agglutinin I binding sites in the neuropil and in synaptic terminals of Purkinje cells. These results in combination with previous studies of intracellular lectin cytochemistry of neurons in the central nervous system demonstrate the similarity of these cells to neuroblastoma cells in their intracellular lectin binding characteristics. Results of the lectin cytochemical studies after neuraminidase digestion of presynaptic terminals support the possibility that neurons may use a post- or extra-Golgi system for the addition of peripheral sugars to the oligosaccharides of certain glycoproteins destined for the cell surface.

Surface localization of an endogenous lectin in rabbit bone marrow

A lectin, which may be involved in cell to cell adhesion during erythropoiesis in rabbit bone marrow, has been isolated and characterized. Several electron microscopical techniques have been used to investigate the cell surface distribution of this lectin in bone marrow utilizing colloidal gold conjugates of anti-lectin IgG or protein A. The lectin is present at the surface of erythroid cells at all stages of development but no lectin was detected on the surface of myeloid cells. The limitations and complementary nature of the techniques used are discussed.

Lectin target cells in human central nervous system and the pituitary gland

Peanut lectin (PNL), Concanavalin A (Con A) and Ulex europaeus lectin I (Ulex) were chosen to map their binding sites in different regions of formalin fixed and paraffin embedded human central nervous system tissue and pituitary gland tissues. An extended PaP method was used for PNL and Ulex, whereas a direct peroxidase technique was employed for Con A. In astrocytes, the cytoplasm as well as the delicate processes were stained by PNL and Con A; the most conspicuous binding of PNL was seen in the ependymal cells and on the surface of plexus epithelial cells; in the anterior part of the pituitary gland a selective population was PNL positive. Intracytoplasmic Con A acceptors could be demonstrated in neurons, in ependymal cells, and in plexus epithelial cells. Intracytoplasmic Con A receptors were finely granular in astrocytes, oligodendrocytes, and in some cells in the pituitary gland. Ulex binding was restricted to the vascular endothelial cells and a selective population of cells in the pituitary gland. Our results suggest that lectins may be good tools for the evaluation of their respective target cells in the central nervous system and in the pituitary gland.

Concanavalin A target cells in human brain tumours

Using a lectin-peroxidase method, Concanavalin A binding was examined on formalin-fixed paraffin-embedded biopsy specimens (n = 143) of the most frequent central nervous system tumours. The brain tumours included oligodendrogliomas, astrocytomas, glioblastomas, ependymomas, neurinomas, meningiomas, medulloblastomas and plexus papillomas. In oligodendroglioma cells, only a weak granular intracytoplasmic staining was observed. The astrocytomas showed a strong reaction in fibrillary astrocytes and in tumour areas undergoing small cystic degeneration. Staining of protoplasmic astrocytes was weaker; pilocytic astrocytes demonstrated poor perinuclear staining. Intracytoplasmic Con A binding in gemistocytic astrocytes was distinct but inconstant and rather diffuse. In the glioblastomas the lymphocyte-like small astrocytes were negative. Giant multinucleated astrocytes stained strongly. In ependymomas no or at most a weak perinuclear reaction was observed, whereas the acceptor density was as high as in the normal ependymocytes in areas where the tumour was capable of producing organotypical structures. Plexus papillomas showed a strong intracytoplasmic staining comparable to the normal plexus epithelial cell. This feature was preserved in the malignant variants. In general, meningiomas and neurinomas were negative. Xanthomatous-degenerated meningioma cells, however, showed a distinct to strong intracytoplasmic staining. This feature was characteristic for the xanthomatous subtype of meningiomas. Granular cells with strong intracytoplasmic Con A staining often occurred at the border of fibrillary to reticular differentiated areas of neurinomas. Medulloblastomas were completely negative. Our results indicate that Con A binding to human brain tumours is specific and rather cytotypical than histotypical . The Con A acceptor density is probably related to the grade of differentiation. Lectin mapping of tumours leads to cytotypical binding patterns which may contribute to the differential diagnosis of neoplasias.

Interactions of lectins with CHO cell surface membranes. II. Differential effects of local anesthetics on endocytosis of Con A and WGA binding sites

Using fibroblastic CHO cells, we have examined 1) the internalization and redistribution of surface binding sites for the lectins Concanavalin A and wheat germ agglutinin and 2) the sensitivity of these processes to putative inhibitors of cytoskeletal activity. Following initial exposure to fluorescein conjugated Con A (CAF) or WGA (WGAF) at 4 degrees C, kinetic analysis of internalization and intracellular aggregation of lectin at 37 degrees C indicated more rapid aggregate formation in the case of WGA than in the case of Con A. Treatment with tertiary amine local anesthetics (tetracaine, dibucaine, and xylocaine) or with a lysosomatrophic amine, m-dansyl cadaverine, blocked internalization of Con A but not of WGA. Similar differential effects on redistribution of Con A and WGA were not however observed with the antimicrotubule agents colchicine and nocodazole. Simultaneous treatment of cells with WGAF and with rhodamine labeled Con A (CAR) resulted in the accumulation of both labels in a central perinuclear aggregate; a similar experiment in the presence of local anesthetic resulted in a diffuse peripheral distribution of CAR and a central aggregate of WGAF. These results suggest 1) CHO cells possess at least two distinct pathways for lectin internalization and redistribution, which can be discriminated in terms of drug sensitivity; 2) CHO cells can sort out and independently internalize different populations of lectin binding sites; and 3) different pathways may be a manifestation of biochemically distinct linkages between cytoskeletal elements and various groups of surface glycoproteins. Present findings concur with our previous results concerning the mutual independence of the surface binding sites for Con A and WGA (Emerson and Juliano, 1982).

Interactions of lectins with CHO cell surface membranes. I. Competition studies indicate concanavalin a and WGA bind to discrete populations of sites

The binding of radioiodinated lectins to the CHO cell surface was measured for the following affinity purified plant agglutinins; concanavalin A, wheat germ agglutinin, Ricinus agglutinins (I, II) pea agglutinin, peanut agglutinin, and Bandeiria simpliciafolia agglutinin (BSLI). The number of binding sites at saturation ranged from 6 x 10(5) for BSL I to 5 x 10(7) for pea and Ricinus. Affinity constants calculated by the Steck-Wallach procedure ranged form 2 x 10(5) m(-1) for pea lectin to 4.5 x 10(5) M(-1) L for peanut lectin. Competition studies between homologous and heterologous radiolabeled and unlabeled lectins indicated that homologous unlabeled lectin could fully block binding of radiolabeled lectin. For heterologous pairs, a variety of results were observed. Of particular interest is the finding that concanavalin A and wheat germ agglutinin mutually failed to compete for binding indicating that these two lectins bind to distinct, nonoverlapping populations of surface sites. This finding suggests that the binding sites for WGA and Con A reside, for the most part, on discrete populations of membrane molecules; this concept is further validated in a companion paper in the upcoming issue of this journal (Schwartz et al., 1982).

Analysis of lectin-specific cell surface glycoprotein on neuroblastoma cells

The binding sites for the lectins wheat germ agglutinin, Ricinus communis agglutinin and concanavalin A on mouse neuroblastoma cell membranes were identified using SDS-gel electrophoresis in combination with fluorescent lectins. Ricinus communis agglutinin and wheat germ agglutinin were found to bind almost exclusively to a single polypeptide with an apparent molecular weight of 30 000. Concanavalin A labeled over 20 different polypeptides, most with molecular weights greater than 50 000. However, when the neuroblastoma cells were treated with concanavalin A so as to internalize all the concanavalin A binding sites visible at the level of the fluorescent microscope and the purified plasma membranes analyzed for their concanavalin A binding polypeptides, only four of the 20 glycopolypeptides were missing or significantly reduced in amount. Thus, these four high molecular weight concanavalin A-binding polypeptides appear to be the major cell surface receptors for concanavalin A. Binding studies with iodinated concanavalin A indicated that these polypeptides represented the high affinity concanavalin A binding sites (Kd = 2 . 10(-7) M). Low affinity concanavalin A binding sites were present on the cell surface after internalization of high affinity concanavalin A binding sites.