The amphoterin (HMGB1)/receptor for advanced glycation end products (RAGE) pair modulates myoblast proliferation, apoptosis, adhesiveness, migration, and invasiveness. Functional inactivation of RAGE in L6 myoblasts results in tumor formation in vivo

We reported that RAGE (receptor for advanced glycation end products), a multiligand receptor of the immunoglobulin superfamily expressed in myoblasts, when activated by its ligand amphoterin (HMGB1), stimulates rat L6 myoblast differentiation via a Cdc42-Rac-MKK6-p38 mitogen-activated protein kinase pathway, and that RAGE expression in skeletal muscle tissue is developmentally regulated. We show here that inhibition of RAGE function via overexpression of a signaling deficient RAGE mutant (RAGE delta cyto) results in increased myoblast proliferation, migration, and invasiveness, and decreased apoptosis and adhesiveness, whereas myoblasts overexpressing RAGE behave the opposite, compared with mock-transfected myoblasts. These effects are accompanied by a decreased induction of the proliferation inhibitor, p21(Waf1), and increased induction of cyclin D1 and extent of Rb, ERK1/2, and JNK phosphorylation in L6/RAGE delta cyto myoblasts, the opposite occurring in L6/RAGE myoblasts. Neutralization of culture medium amphoterin negates effects of RAGE activation, suggesting that amphoterin is the RAGE ligand involved in RAGE-dependent effects in myoblasts. Finally, mice injected with L6/RAGE delta cyto myoblasts develop tumors as opposed to mice injected with L6/RAGE or L6/mock myoblasts that do not. Thus, the amphoterin/RAGE pair stimulates myoblast differentiation by the combined effect of stimulation of differentiation and inhibition of proliferation, and deregulation of RAGE expression in myoblasts might contribute to their neoplastic transformation.