Characterisation of Myogenic Cell Membrane: Ii. Dynamic Changes in Membrane Lipids During the Differentiation of Mouse C2 Myoblast Cells

Abstract

Proliferating mouse C2 myoblast cells resist haemagglutinating virus of Japan, Sendai virus (HVJ) mediated cell fusion. However, differentiating C2 cells can be induced to fuse by HVJ, suggesting that the rigid membrane of C2 cells changes during the differentiation. To investigate this phenomenon, changes in membrane lipids which affect fluidity were examined. Membrane cholesterol gradually decreased with the differentiation of C2 cells. However, spontaneous fusion to form myotubes and artificial fusion induced by HVJ were both inhibited when the level of cholesterol was prevented from falling in the cell membrane. The membranes of differentiating C2 cells contained more unsaturated fatty acids than those of proliferating cells. Thus, when differentiating C2 cells were treated with stearate (a saturated fatty acid), they failed to form myotubes and were insensitive to HVJ-mediated fusion. Whereas, if proliferating C2 cells were given linolenate (an unsaturated fatty acid), they became capable of HVJ-induced fusion. These results indicate that differentiating C2 cells change their fusion sensitivity by decreasing cholesterol, probably at the same time as they increase the unsaturated fatty acid content of the cell membrane.

Cholesterol Modulates the Rate and Mechanism of Acetylcholine Receptor Internalization

“…In a similar manner to when CHO/K1-A5 cells are treated with CDx, membrane cholesterol gradually decreases up to ϳ45% with the differentiation of C2 cells, such decrease being necessary for myoblast fusion (49). Chol levels are subsequently recovered and become important in both the formation and stabilization of agrin-induced AChR clusters (11)(12)(13).…”

Neural Stem Cells

“…6 These frequencies are orders of magnitude higher than the fusion efficiency between ES and somatic stem cells. Particularly, concerning brain into muscle conversion, the possibility that cell fusion might be responsible for transdifferentiation seems more remote, due to the following facts: (1) proliferating C2 myoblasts are strongly resistant even to Sendai virus-mediated cell fusion; 97 (2) myoblasts fuse with other myoblasts only when both are committed to differentiation and not when they are still proliferating 98 as in our experimental paradigm; 6 (3) myoblasts do not normally fuse with nonmyogenic cells 98 and, on this rare event, the fusion of a myocyte with a nonmyogenic cells generally results in the extinction of muscle-specific properties in the immediate fusion product, 99 and (4) in our in vitro model, we observed high frequency of mononucleated NSC-derived myocytes. 6 Thus, the chances that cell fusion between NSCs and inducing myoblasts might occur spontaneously are quite low.…”

K252a, an Indrocarbazole Derivative, Causes the Membrane of Myoblasts to Enter a Fusion-Capable State

“…The amount of membrane cholesterol was measured based on the reaction whereby cholesterol oxidase converts cholesterol into cholestenon that is absorbed at 237 nm (21). The amount was obtained as g/mg of protein as described previously (20).…”

“…The results suggest that the membrane of myoblasts enters a fusion-capable state for the formation of myotubes during differentiation. We recently showed that the components of membrane lipids are closely related to the change in myoblast membrane during the differentiation; a rise in membrane fluidity caused by a decrease of cholesterol and increase of unsaturated fatty acids is necessary for myoblast fusion (20).…”