The role of syndecan-4 and attached glycosaminoglycan chains on myogenic satellite cell growth.
The syndecans are a family of cell-surface heparan sulfate proteoglycans consisting of a core protein with covalently attached glycosaminoglycan (GAG) chains. Syndecan-4 expression in skeletal muscle is increased in growth-selected animals during proliferation. Previous studies have suggested that cell-surface heparan sulfate proteoglycans like syndecan-4 are involved in fibroblast growth factor 2 (FGF2) signaling by FGF2 binding to the heparan sulfate chains. Fibroblast growth factor 2 is a potent stimulator of muscle proliferation and an intense inhibitor of differentiation. To investigate the functional contribution of the attached syndecan-4 GAG chains, a turkey syndecan-4 full length cDNA was cloned and mutated at two or all three potential GAG attachment sites at Ser38, Ser65, and Ser67 resulting in all possible one-chain mutants and a no-chain mutant. Turkey satellite cells were transfected with the wild-type syndecan-4, one-chain mutants, no-chain mutant, or the empty vector and assayed for cell proliferation, differentiation, and FGF2 responsiveness. The wild-type syndecan-4, one-chain mutants, and no-chain mutant inhibited cell proliferation and delayed initial differentiation but did not alter FGF2 responsiveness or function through the mitogen-activated protein kinase pathway. There was no difference between the wild-type syndecan-4, one-chain, and no-chain mutants during these stages. These data suggest that syndecan-4 functions in an FGF2-independent manner and the GAG chains attached to the syndecan-4 core protein are not required for syndecan-4 to affect turkey satellite cell proliferation and the initial differentiation.
Zhang
Xiangfeng
X
Department of Animal Sciences, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA.
Nestor
Karl E
KE
McFarland
Douglas C
DC
Velleman
Sandra G
SG
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D049109:Cell Proliferation; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D006025:Glycosaminoglycans / Q000378:metabolism*; D006497:Heparan Sulfate / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D032496:Satellite Cells, Skeletal Muscle / Q000166:cytology*; D053671:Syndecan-4 / Q000378:metabolism / Q000502:physiology*; D014422:Turkeys
D016222:Fibroblast Growth Factor 2; D006025:Glycosaminoglycans; D006497:Heparan Sulfate; D053671:Syndecan-4