Interactions of ganglioside GM1 with human and fetal calf sera. Formation of ganglioside-serum albumin complexes

The interactions of ganglioside G_M1 with human and fetal calf sera were studied, the following main results being obtained: (a) G_M1, upon incubation with both sera gave origin to two G_M1-protein complexes, which also occurred after interaction of G_M1 with the albumin fractions prepared from the same sera. Instead no complex formation occurred using the albumin-free fractions. Therefore G_M1 appeared to specifically bind serum albumin and to form G_M1-albumin complexes. (b) G_M1 binding to serum albumin started at ganglioside concentrations surely micellar (above 10^?6 M), was time and concentration dependent, and resulted in a relevant degree of G_M1 complexation (up to 80% of total G_M1 in human serum and up to 18% in fetal calf serum). (c) the binding kinetics appeared, in both serum and the correspondent albumin fraction, to be biphasic: in the first phase, occurring till about 2 · 10^?4 M G_M1, the ratio between bound and total G_M1 increased linearly with increasing G_M1 concentration; in the second phase, occurring above 2 · 10^?4 M, the ratio remained practically constant. After these findings it should be expected that G_M1, when present in serum containing systems, forms complexes with albumin. This should be appropriately considered when studying the effects of exogeneous G_M1 in in vivo and in vitro (tissue cultures) systems.     

Preparation of the tritiated molecular forms of gangliosides with homogeneous long chain base composition

Gangliosides G_M2, G_M1 and G_D1b were radiolabelled at C-6 of the terminal galactose orN-acetylgalactosamine by the galactose oxidase/[³H]NaBH₄ method; gangliosides G_M2, G_M1, Fuc-G_M1 and G_D1a were radiolabelled at C-3 of the long chain base by the 2,3-dichloro-5,6-dicyanobenzoquinone/[³H]NaBH₄ method.By application of an original HPLC procedure, eight different molecular species were prepared from each labelled ganglioside. Each of these species was characterized by the presence of one of the following long chain bases:erythro C18 sphingosine,threo C18 sphingosine,erythro C18 sphinganine,threo C18 sphinganine,erythro C20 sphingosine,threo C20 sphingosine,erythro C20 sphinganine andthreo C20 sphinganine.From G_D1b only the species containing theerythro forms of long chain bases were obtained.The individual molecular species were more than 99% homogeneous and had a radiopurity better than 99%. The molecular species of the same ganglioside, radiolabelled at C-3 of the long chain base, had identical specific radioactivity, namely 1.17, 1.25, 0.85 and 1.28 Ci/mmol for G_M2, G_M1, Fuc-G_M1 and G_D1a respectively. The molecular species of the same ganglioside, radiolabelled at C-6 of terminal galactose orN-acetylgalactosamine, had similar specific radioactivity, namely 1.34–1.40, 1.44–1.51, 1.37–1.44 Ci/mmol for G_M2, G_M1 and G_D1b respectively.     

Formation and turnover of myelin ganglioside

—In young adult rats, the formation and turnover of G_M1-ganglioside in myelin were compared with the formation and turnover of G_M1-ganglioside in whole brain and of total lipids in whole brain and myelin, after injection of d-[1-¹⁴C]glucosamine. During the first 24 hr after injection, the specific activity of G_M1-ganglioside in myelin was less than 25 per cent of that of G_M1-ganglioside in whole brain. The specific activity of ganglioside in whole brain was maximal at 24 hr and then declined steadily during the next 3 months, whereas the specific activity of G_M1-ganglioside in myelin continued to increase and did not reach a peak until about one month after injection, by which time its specific activity had increased five-fold. Consequently, the specific activity of G_M1-ganglioside in myelin was 50 per cent higher than ganglioside in whole brain after one month. These differences in the formation and turnover of G_M1-ganglioside in myelin and of whole brain are similar to those of other lipids of myelin and of whole brain, indicating that the metabolic activity of myelin ganglioside is similar to myelin lipids, but differs from whole brain lipids or whole brain gangliosides. These data provide additional evidence that ganglioside in myelin is an intrinsic constituent of the myelin sheath. G_T1 (G₁), G_D1b, (G₂), G_D1a (G₃), G_M1 (G₄), G_M2 (G₅), G_M3 (G₆).     

Substrate specificities of a bacterial sialidase and rat liver ganglioside GM3 sialyltransferase

Sialidases cleave off sialic acid residues from the oligosaccharide chain of gangliosides in their catabolic pathway while sialyltransferases transfer sialic acid to the growing oligosaccharide moiety in ganglioside biosynthesis. Ganglioside G_M3 is a common substrate for both types of enzymes, for sialidase acting on ganglioside G_M3 as well as for ganglioside G_D3 synthase. Therefore, it is possible that both enzymes recognize similar structural features of the sialic acid moiety of their common substrate, ganglioside G_M3. Based on this idea we used a variety of G_M3 derivatives as glycolipid substrates for a bacterial sialidase (Clostridium perfringens) and for G_D3 synthase (of rat liver Golgi vesicles). This study revealed that those G_M3 derivatives that were poorly degraded by sialidase also were hardly recognized by sialyltransferase (G_D3 synthase). This may indicate similarities in the substrate binding sites of these enzymes.     

Genetic control of “natural” killer lymphocytes in the mouse

Spleens from normal young mice contain lymphocytes that can kill certain in vitro grown Moloney lymphoma lines in a⁵¹Cr-release cytotoxicity test. A lymphoid cell without detectable T- or B-cell markers was previously shown to be responsible. Killing activity shows a marked dependence on the genotype of the donor mouse. When tested against a YAC line of strain A origin maintained in vitro spleens of A, A.CA, and A.SW mice had low activity, whereas CBA, C3H, C57L, and C57Bl spleens were highly active. In semisyngeneic F₁ crosses with strain A as one parent, reactivity resembled the opposite parental strain. Thus, (A×CBA)F₁, (A×C3H)F₁, (A×C57L)F₁, and (A×C57Bl)F₁ were reactive, whereas A×A.CA showed no significant activity. Analysis of the reactivity in (A×C57Bl)F₁×A backcross mice suggests that multiple genes are involved. Preliminary linkage analysis suggests at least oneH-2 linked factor. Another gene appears to be linked to theB (black) locus.     

Mouse liver and lung glutathione S-epoxide transferase: Effects of phenobarbital and 3-methylcholanthrene administration

The effects of 3-methylcholanthrene (3MC) and phenobarbital (PB) administration on the levels of glutathione-S-epoxide transferase activity in supernatant preparations of liver and lung were studied in a number of different strains of mice, C57Bl/6, C3H, C3H_f^?, Balb/c^?, A⁺ and DBA/2⁺. Three epoxide substrates, 3MC-11,12-oxide, styrene oxide (SO) and 3,3,3-trichloro-1,2-epoxypropane (TCPO), were employed in this investigation. PB administration (75 mg/kg body weight for 3 days) resulted in 13–57% increases in enzyme activity in the liver supernatant but was ineffective in inducing activity in lung. 3MC administration (40 mg/kg body weight for 2 days) on the other hand was without any effect on glutathione-S-epoxide transferase activity in both liver and lung.     

Mixed lipid aggregates containing gangliosides impose different 2H-NMR dynamical parameters on water environment depending on their lipid composition

Water dynamics in samples of ceramide tetrasaccharide (G_g4Cer) vesicles and G_M1 ganglioside micelles at 300:1 water/lipid mole ratio were studied by using deuterium nuclear magnetic resonance (²H-NMR). G_M1 imposes a different restriction on water dynamics that is insensitive to temperatures either above or below its phase transition temperature or below the freezing point of water. The calculated correlation times are in the range of 10^?10 s, typical of water molecules near to the polar groups. Pure G_M1 micelles have two distinct water microenvironments dynamically characterized. Their dynamic parameters remain constant with temperature ranging from ?18 to 32°C, but the amount of strongly associated water is modified. By contrast, a mixture of single soluble carbohydrates corresponding to G_M1 polar head group does not preserve the dynamic parameters of water hydration when the temperature is varied. Incorporation of cholesterol or lysophosphatidylcholine into G_M1 micelles substantially increases the mobility of water molecules compared with that found in pure G_M1 micelles. The overall results indicate that both the supramolecular organization and the local surface quality (lipid–lipid interaction) strongly influence the interfacial water mobility and the extent of hydration layers in glycosphingolipid aggregates.     

GM2-Ganglioside Metabolism In Situ in Mucolipidosis IV Fibroblasts

Mucolipidosis IV (ML IV) is an inherited lysosomal disorder for which the primary biochemical defect has not been identified. In order to detect any defect in glycosphingolipid metabolism, we have examined the metabolism of sphingosine-labeled (³H)G_M2 in situ in fibroblasts from patients diagnosed with ML IV. Fibroblasts were exposed for 10 days in medium containing (³H)G_M2 (15 uM; Sp. Act. 35000 cpm/nmole), washed, harvested and analyzed for radioactivity in extracted lipids. Control cells metabolized about half of the internalized ganglioside, mostly to ceramide. In ML IV fibroblasts, 70–80% of the cellular radioactivity was present as G_M2 indicating reduced degradation. This is not as severe as in G_M2 gangliosidosis as a small amount of G_M2 was metabolized in ML IV cells to ceramide. Since there is no defect in the lysosomal enzyme profile in these cells, it is possible that an abnormality in the translocation of membrane constituents to the lysosomes may explain the slower ganglioside metabolism.     

Determination of sialidase activities in HeLa cells using gangliosides specifically labeled in N-acetylneuraminic acid.

Radioactive gangliosides, N-[¹⁴C]-acetylneuraminylgalactosylglucosylceramide ([¹⁴C]G_M3) and N- [¹⁴C]-acetylneuraminylgalactosyl-N-acetylgalactosaminyl- [N-acetylneuraminyl]-galactosylglucosylceramide ([¹⁴C]G_D1a), were synthesized from CMP-[¹⁴C]sialic acid and the appropriate precursor glycolipid using specific sialyltransferase activities. These compounds were isolated and used as substrates to assay sialidase activity in HeLa cells. Although sodium butyrate added to the culture medium increased G_M3 biosynthesis in HeLa cells, sialidase activity, as well as that of other glycohydrolases, was the same in control and butyrate-treated HeLa cells. The same sialidase activity appeared to hydrolyze both [¹⁴C]G_M3 and [¹⁴C]G_D1a, but not fetuin; the enzyme had a pH optimum of 5.0 and a K_m of 75 μm for the ganglioside substrates. Although the cells contained a high sialidase activity (4–7 nmol/mg of protein/h) and could bind exogenously added [¹⁴C]G_M3, no “ecto”-sialidase activity would be detected in intact cells under conditions where a close to physiological pH is maintained. The results indicate that ganglioside sialidase is not involved directly in the morphological and biochemical differentiation induced in HeLa cells by exposure to sodium butyrate.     

Fucosyl-GM1 — A ganglioside associated with small cell lung carcinomas

Characterization of monosialogangliosides of a small cell lung carcinoma showed a unique composition. The tumour contained G_M2 and Fucosyl-G_M1 (Fuc-G_M1) with 2-hydroxy fatty acids as major ganglioside components. Three out of four other small cell carcinomas analysed contained also Fuc-G_M1 as a characteristic ganglioside. Fuc-G_M1 is suggested to be a small-cell lung carcinoma associated ganglioside antigen.Nomenclature: The gangliosides have been designated according to Svennerholm [25] G_M3 II³NeuAc-Lac-Cer - G_D3 II³(NeuAc)₂-LacCer - G_M2 II³NeuAc-GgOse₃Cer - G_M1 II³NeuAc-GgOse₄Cer - Fuc-G_M1 FuclV²Neu-AcII³-GgOse₄Cer - 3-L_M1 IV³NeuAc-nLcOse₄Cer - 6-L_M1 IV⁶NeuAc-nLcOse₄Cer     

STALOSYLGALACTOSYL CERAMTDE AS A SPECIFIC MARKER FOR HUMAN MYELIN AND OLIGODENDROGLIAL PERIKARYA: GANGLIOSIDES OF HUMAN MYELIN, OLIGODENDROGLIA AND NEURONS

Gangliosides were isolated from human brain myelin, oligodendroglia, and neurons. Quantitative analysis revealed the following ganglioside contents: myelin, 2.0; neurons, 1.3; and oligodendroglia, 0.35 μg ganglioside sialic acid per mg protein. Myclin had a relatively simple ganglioside pattern with G_M4 and G_M1 as the predominant ganglioside species. The ganglioside pattern of oligodendroglia was quite complex and it resembled that of whole white matter rather than that of myelin. A high concentration of G_M4 was found in oligodendroglial fractions in addition to G_M1, G_D1a, G_D1b, and G_T1b. The usually- minor brain gangliosides G_M3, G_M2, and G_M3 were also enriched in oligodendroglia. The neuronal ganglioside pattern was generally similar to the pattern of whole gray matter. Both neurons and whole gray matter contained very low amounts of G_M4. These results indicate that G_M4 is specifically localized in myelin and oligodendroglia of the CNS. Evidence is also presented that myelin, but not oligodendroglia, is the major reservoir of human white matter G_M1 and G_M4.     

Sialylation and Muscle Performance: Sialic Acid Is a Marker of Muscle Ageing

Sialic acids (Sia) are widely expressed as terminal monosaccharides on eukaryotic glycoconjugates. They are involved in many cellular functions, such as cell–cell interaction and signal recognition. The key enzyme of sialic acid biosynthesis is the bifunctional UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (GNE), which catalyses the first two steps of Sia biosynthesis in the cytosol. In this study we analysed sialylation of muscles in wild type (C57Bl/6 GNE ^+/+) and heterozygous GNE-deficient (C57Bl/6 GNE ^+/−) mice. We measured a significantly lower performance in the initial weeks of a treadmill exercise in C57Bl/6 GNE ^+/− mice compared to wild type C57Bl/6 GNE ^+/+animals. Membrane bound Sia of C57Bl/6 GNE ^+/− mice were reduced by 33–53% at week 24 and by 12–15% at week 80 in comparison to C57Bl/6 GNE ^+/+mice. Interestingly, membrane bound Sia concentration increased with age of the mice by 16–46% in C57Bl/6 GNE ^+/+, but by 87–207% in C57Bl/6 GNE ^+/−. Furthermore we could identify specific morphological changes in aged muscles. Here we propose that increased Sia concentrations in muscles are a characteristic feature of ageing and could be used as a marker for age-related changes in muscle.     

Insertion of ganglioside GM1 into rat glioma C6 cells renders them susceptible to growth inhibition by the B subunit of cholera toxin

The B subunit of cholera toxin does not affect the growth of rat glioma C6 cells which are deficient of its receptor, ganglioside G_M1. Insertion of ganglioside G_M1 into the plasma membrane of C6 cells renders them susceptible to inhibition of DNA synthesis by the B subunit. Exposure of C6 cells to butyrate induces an elevation of ganglioside G_M1 as measured by an increase in binding of iodinated cholera toxin and also results in an inhibition of DNA synthesis by the B subunit. The extent of inhibition of DNA synthesis correlated with the binding of B subunit and was independent of adenylate cyclase activation or increases in intracellular cAMP levels.     

Visualization of domains in rigid ganglioside / phosphatidylcholine bilayers: Ca2+ effects

We have considered the extent to which details of lectin binding directly visualized by freeze-etch electron microscopy are consistent with current concepts of ganglioside arrangement in phosphatidylcholine bilayer membranes. Native lectins in general seem appropriate labels for this type of study. Wheat germ agglutinin, Ricinus communis agglutinin, and peanut agglutinin are adequately resolved on membrane surfaces as spherical particles of diameters 6 nm, 10 nm, and 13 nm, respectively (uncorrected for platinum shadow thickness). The finite areas covered by these markers correspond to some 56, 157, and 265 lipid molecules, respectively, on the surfaces of the shadowed rigid phosphatidylcholine matrices employed here; and this constitutes a basic limitation to the precision with which one can localize a given glycolipid receptor. Ricinus communis agglutinin provides a marker whose size permits adequate quantitation of bound material while minimally obscuring detail. Using it we estimated the size limits of G_M1-enriched domains, since this is the ganglioside which has shown the greatest evidence of discontinuous distribution in our hands (Peters, M.W., Mehlhorn, I.E., Barber, K.R. and Grant, C.W.M. (1984) Biochim. Biophys. Acta 778, 419–428). Results of such analyses indicate the probable existence of phase separated domains selectively enriched in G_M1 up to 60 nm in extent (5600 lipid molecules) for rigid dipalmitoylphosphatidylcholine membranes bearing up to 14 mol% G_M1. Similar observations were true of rigid bilayers of dimyristoylphosphatidylcholine; however, if domains enriched in G_M1 exist in fluid dimyristoylphosphatidylcholine, they are on the order of 6 nm or less in diameter (or are dispersed by lectin binding). Employing the small lectin, wheat germ agglutinin, which binds to all gangliosides, we then examined the effect of exposure to Ca²⁺ ions (while in the fluid state) on the ganglioside ‘domain structure’ referred to above in rigid dipalmitoylphosphatidylcholine host matrices. G_M1, G_D1a and G_T1b were studied at 0, 2 and 10 mM Ca²⁺ concentrations. It was demonstrated by spin label measurements that the dipalmitoylphosphatidylcholine matrix retained its basic melting characteristics in the presence of added Ca²⁺ and ganglioside under these conditions. Within the technique's functional resolution limit of some 6 nm we were unable to identify any effect of Ca²⁺ in physiological concentration on ganglioside topography as reflected by bound lectin distribution. The rigid dipalmitoylphosphatidylcholine host matrix had been selected to minimize receptor redistribution (ganglioside aggregation or disaggregation) caused by lectin probe binding or sample preparation for electron microscopy. However the above Ca²⁺-related observations were basically unaltered in a matrix of intermediate fluidity and zero cooperativity obtained by the addition of 30 mol% cholesterol. In none of our samples did we see bilayer disruption that might indicate significant patches of very high local glycosphingolipid concentration.     

Purification and properties of the hexosaminidase A-activating protein from human liver

Human liver extracts contain an activating protein which is required for hexosaminidase A-catalysed hydrolysis of the N-acetylgalactosaminyl linkage of G_M2 ganglioside [N-acetylgalactosaminyl-(N-acetylneuraminyl) galactosylglucosylceramide]. A partially purified preparation of human liver hexosaminidase A that is substantially free of G_M2 ganglioside hydrolase activity is used to assay the activating protein. The proceudres of heat and alcohol denaturation, ion-exchange chromatography and gel filtration were used to purify the activating protein over 100-fold from crude human liver extracts. When the purified activating protein is analysed by polyacrylamide-gel disc electrophoresis, two closely migrating protein bands are seen. When purified activating protein is used to reconstitute the G_M2 ganglioside hydrolase activity, the rate of reaction is proportional to the amount of hexosaminidase A used. The activation is specific for G_M2 ganglioside and and hexosaminidase A. The activating protein did not stimulate hydrolysis of asialo-G_M2 ganglioside by either hexosaminidase A or B. Hexosaminidase B did not catalyse hydrolysis of G_M2 ganglioside with or without the activator. Kinetic experiments suggest the presence of an enzyme–activator complex. The dissociation constant of this complex is decreased when higher concentrations of substrate are used, suggesting the formation of a ternary complex between enzyme, activator and substrate. Determination of the molecular weight of the activating protein by gel-filtration and sedimentation-velocity methods gave values of 36000 and 39000 respectively.     

Topographic studies of gangliosides of intact synaptosomes from rat brain cortex

Gangliosides in the external surface of intact synaptosomes from rat brain cortex have been studied by oxidation of exposed galactose and galactosamine groups with galactose oxidase followed by reduction with labeled sodium borohydride. Purified synaptosomes were labeled, disrupted by osmotic shock, and the particulate components fractionated on diatrizoate to give four synaptosomal membrane fractions (A-D) and a mitochondrial pellet (E). Fractions A and B represent synaptosomal plasma membranes. When intact synaptosomes were labeled, the major portion of the total radioactivity incorporated into ganglioside fraction was found to be in G _M1 ³ species. With isolated membrane fractions little selectivity was seen: (1) more label was present compared to intact synaptosomes, and (2) zones corresponding to G_M2, G_M1, G_D1a, G_D1b were the major gangliosides labeled. The results confirm the conclusion that membrane fractions A and B are derived from the exposed synaptosome surface and also show that G_M1 is the major ganglioside species available for enzyme oxidation at the surface.     

A novel radiosensitive SCID patient with a pronounced G2/M sensitivity

V(D)J rearrangement in lymphoid cells involves repair of double-strand breaks (DSBs) through non-homologous end joining (NHEJ). Defects in this process lead to increased radiosensitivity and severe combined immunodeficiency (RS-SCID). Here, a SCID patient, M3, is described with a T^?B⁺NK⁺ phenotype but without causative mutations in CD3δ, ?, ζ or IL7Rα, genes specifically involved in T cell development. Clonogenic survival of M3 fibroblasts showed an increased sensitivity to the DSB-inducing agents ionizing radiation and bleomycin, as well as the crosslinking compound, mitomycin C. We did not observe inactivating mutations in known NHEJ genes and results of various DSB-repair assays in G₁ M3 cells were indistinguishable from those obtained with normal cells. However, we found increased chromosomal radiosensitivity at the G₂ phase of the cell cycle. Checkpoint analysis indicated functional G₁/S and intra-S checkpoints after irradiation but impaired activation of the “early” G₂/M checkpoint. Together these results indicate a novel class of RS-SCID patients characterized by the specific absence of T lymphocytes and associated with defects in G₂-specific DSB repair. The pronounced G₂/M radiosensitivity of the RS-SCID patient described here, suggests a defect in a putative novel and uncharacterized factor involved in cellular DNA damage responses and T cell development.     

Shedding of Gangliosides by Human Medulloblastoma Cells

Shedding of immunosuppressive gangliosides is an important characteristic of both experimental and human tumors. Using a medulloblastoma cell line, Daoy, with a very high ganglioside expression (141 ± 13 nmol/10⁸cells) and a well-characterized ganglioside complement, we have now studied ganglioside shedding by human brain tumor cells. Shedding of gangliosides, quantified by metabolic radiolabeling, was significant (169 pmol/10⁸cells/h) and was generalized with respect to the major ganglioside carbohydrate structures (G_M2, G_M3, and G_D1a). For each ganglioside, however, shedding was selective for ceramide structures containing shorter fatty acyl chains. Rapid and ceramide-selective shedding was confirmed in two additional human medulloblastoma cell lines, D341 Med and D283 Med (112 and 59 pmol/10⁸cells/h). Significant ganglioside shedding is therefore a common characteristic of human medulloblastoma cells and may influence the biological behavior of this tumor, in view of immunosuppressive and other biological properties of shed gangliosides.     

Metabolism of GM1 ganglioside in cultured skin fibroblasts: anomalies in gangliosidoses,sialidoses, and sphingolipid activator protein (SAP,saposin) 1 and prosaposin deficient disorders

Summary Cultured skin fibroblasts from controls and patients with lysosomal storage diseases were loaded with G_M1 ganglioside that had been labelled with tritium in its ceramide moiety. After a 65-h or 240-h incubation, a large percentage of this ganglioside remained undegraded in G_M1 gangliosidoses, whereas in the other storage diseases studied, one of its metabolites accumulated by 2–4 fold relative to controls. Labelled G_M2 ganglioside accumulated in 4 variants of G_M2 gangliosidosis, whereas labelled G_M3 ganglioside accumulated in sialidosis, galactosialidoses and sphingolipid activator protein 1 (SAP-1, saposin B) and prosaposin (saposin A, B, C an D) deficient lipidoses. The reduced degradation of G_M3 ganglioside in the SAP-1 and prosaposin deficiencies was attributed to the deficient function of SAP-1. The prosaposin deficient cells also showed a reduced re-utilization of radioactive metabolites from G_M1 ganglioside (i.e. sphingosine and fatty acid) for phospholipid biosynthesis compared with fibroblasts from the SAP-1 deficient patient or normal controls. This anomaly was ascribed to the previously shown defect in ceramide degradation in prosaposin deficiency.     

Novel structural insights into rotavirus recognition of ganglioside glycan receptors

Rotaviruses ubiquitously infect children under the age of 5, being responsible for more than half a million diarrhoeal deaths each year worldwide. Host cell oligosaccharides containing sialic acid(s) are critical for attachment by rotaviruses. However, to date, no detailed three-dimensional atomic model showing the exact rotavirus interactions with these glycoconjugate receptors has been reported. Here, we present the first crystallographic structures of the rotavirus carbohydrate-recognizing protein VP8^? in complex with ganglioside G_M3 glycans. In combination with assessment of the inhibition of rotavirus infectivity by N-acetyl and N-glycolyl forms of this ganglioside, our results reveal key details of rotavirus-ganglioside G_M3 glycan recognition. In addition, they show a direct correlation between the carbohydrate specificities exhibited by VP8^? from porcine and by monkey rotaviruses and the respective infectious virus particles. These novel results also indicate the potential binding interactions of rotavirus VP8^? with other sialic acid-containing gangliosides.