Purified lectin from skeletal muscle inhibits myotube formation in vitro.

Abstract

A lactose-extractable lectin obtained from 14-16-d embryonic chick pectoral muscle and myotube muscle cultures by affinity chromatography inhibited myotube formation in culture . When applied to muscle cultures at 0 .09 Itg/ml, the purified lectin produced variable effects on the inhibition of myotube formation related to the time and length of application, suggesting that components of the culture medium and/or temperature produced inactivation . Hemagglutination assays showed that the lectin was inactivated by horse serum and by chick embryo extract but not by L-15 salt solution at 4°C . Incubation in L-15 solution at 37°C with or without 2 mM dithiothreitol resulted in inactivation in 2-3 h . To maximize the effect of the lectin on the inhibition of myotube formation, primary muscle cultures were grown in low [Ca"] medium to inhibit fusion, and then [Ca +2] was increased to elicit fusion in the absence and presence of lectin with solution renewal every 2 h. Without lectin, myotube formation was normal, whereas, with lectin, it was inhibited by 93% . Continued incubation at 37°C without renewal of lectin resulted in myotube formation, suggesting reversibility by lectin inactivation.It has been postulated that embryonic cells employ the appearance and/or disappearance of surface constituents during their development for specific tissue recognition (17,24,29) . Evidence for the appearance of such factors has been obtained for retinal cells and, more recently, for retinal cell membranes that show specificity for type, developmental stage, and absence of recognition factors in older embryos (8, 9) . Multivalent glycoproteins that promote species-specific sponge cell aggregation (10) and molecules that appear to be the receptors for these ligands on the cell surfaces (28) have been isolated in pure form . Simpson et al . (25) have characterized and purified a galactosebinding protein, discoidin, from the slime mold Dictyostelium discoideum in which the biosynthesis closely parallels the development of cell cohesiveness . Species-specificity is suggested because an-J . CELL BIOLOGY © The Rockefeller University Press -0021-9525/80/06/0617/09 $1 .00 Volume 85 June 1980 617-625 other slime mold, Polysphondylium pallidum, also contains a developmentally regulated cell surface lectin that reacts with species-specific cell surface oligosaccharides during cellular cohesion (26) .A /3-D-galactoside-specific lectin occurs in embryonic chick pectoral muscle and skeletal muscle cultures (4,7,19,27). The highest concentration appears between 8 and 16 d of development (19), which is also the period of highest myoblast fusion, suggesting a possible correlation between the lectin and the recognition-fusion process. The hemagglutinating activity of this lectin is inhibited by lactose and thiodigalactoside . Primary cultures of chicken (6) and rat skeletal (4) muscle are unaffected by thiodigalactoside ; however, the rat muscle cell lines L 6 (4, 7) and L 8 (4) are fusion inhibited .The objective of this study was to deter...

Inhibition of myoblast differentiation in vitro by a protein isolated from liver cell medium.

“…With the exception of the inhibitor of fusion in CEE described by Slater (3), the DI does not appear to correspond to inhibitors of fusion previously described in the literature . Its lack of hemagglutinating activity, as well as its heat and acid stability, contrasts sharply with the lectins studied by several other groups (20)(21)(22)(23)(24). The lectin with properties closest to those we have observed is probably Podleski's "myonectin", but the DI is quite stable to exhaustive dialysis, is relatively heat-stable, and is not inactivated as a result of the loss of a small stabilizing molecule during gel filtration; all of these differ from myonectin (24; T. R. Podleski, personal communication) .…”

Lectins facilitate calcium‐induced fusion of phospholipid vesicles containing glycosphingolipids

“…Authors in [26] suggested that a membrane-bound lectin is involved in the fusion of L6 myoblasts; authors in [27] however, found evidence to the contrary in chick embryo myoblasts. Authors in [28] reported that a lectin from chick embryo skeletal muscle is inhibitory to the fusion of myoblasts, but have suggested that it may mediate cell-cell contact. It remains to be investigated whether the recognition of intracellular membranes before their fusion with each other is mediated by membrane-bound lectin-like molecules.…”

The fusion of myoblasts

“…Soluble electronectin activity is regulated by a second protein, myonectin, which also undergoes a transient increase before fusion. Importantly an electronectin-like P-D-galactoside-binding protein has been isolated from chick embryonic muscle (Den & Malinzak, 1977;Nowak et al, 1977;MacBride & Przybylski, 1980). It has been claimed that this endogenous lectin is involved in fusion, since the f-D-galactoside-binding protein has been shown to inhibit fusion in aligned myoblasts (Gartner & Podleski, 1975;MacBride & Przybylski, 1980).…”

“…Importantly an electronectin-like P-D-galactoside-binding protein has been isolated from chick embryonic muscle (Den & Malinzak, 1977;Nowak et al, 1977;MacBride & Przybylski, 1980). It has been claimed that this endogenous lectin is involved in fusion, since the f-D-galactoside-binding protein has been shown to inhibit fusion in aligned myoblasts (Gartner & Podleski, 1975;MacBride & Przybylski, 1980). This role has been disputed, however (Den et al, 1976;Kaufman & Lawless, 1980), and Den & Chin (1981) have been unable to detect the lectin on the myoblast cell surface.…”