Effects of gangliosides on the differentiation of human mesenchymal stem cells into osteoblasts by modulating epidermal growth factor receptors.
Gangliosides are sialic acid-conjugated glycosphingolipids that are believed to regulate cell differentiation as well as the signals of several signal molecules, including epidermal growth factor receptors (EGFR). These compounds are localized in a glycosphingolipid-enriched microdomain on the cell surface and regulated by the glycosphingolipid composition. However, the role that gangliosides play in osteoblastogenesis is not yet clearly understood, therefore, in this study, the relationship between gangliosides and EGFR activation was investigated during osteoblast differentiation in human mesenchymal stem cells (hMSCs). The results of high-performance thin-layer chromatography (HPTLC) showed that ganglioside GM3 expression was decreased, whereas ganglioside GD1a expression was increased during the differentiation of hMSCs into osteoblasts. In addition, an increase in the activation of alkaline phosphatase (ALP) was observed in response to treatment with EGF (5 ng/ml) and GD1a (1 microM) (p<0.05). The activation of ALP was significantly elevated in response to treatment of ganglioside GD1a with EGF when compared to control cells (p<0.01). However, treatment with GM3 (1muM) resulted in decreased ALP activation (p<0.01), and treatment of hMSCs with a chemical inhibitor of EGFR, AG1478, removed the differential effect of the two gangliosides. Moreover, incubation of the differentiating cells with GD1a enhanced the phosphorylation of EGFR, whereas treatment with GM3 reduced the EGFR phosphorylation. However, AG1478 treatment inhibited the effect of ganglioside GD1a elicitation on EGFR phosphorylation. Taken together, these results indicate that GD1a promotes osteoblast differentiation through the enhancement of EGFR phosphorylation, but that GM3 inhibits osteoblast differentiation through reduced EGFR phosphorylation, suggesting that GM3 and GD1a are essential molecules for regulating osteoblast differentiation in hMSCs.
Kim
Sun-Mi
SM
Department of Biological Science, College of Natural Sciences, Wonkwang University, 344-2 Shinyong-dong, Iksan, Jeonbuk 570-749, Republic of Korea.
Jung
Ji-Ung
JU
Ryu
Jae-Sung
JS
Jin
Jung-Woo
JW
Yang
Hyo-Jung
HJ
Ko
Kisung
K
You
Hyung-Keun
HK
Jung
Kyu-Yong
KY
Choo
Young-Kug
YK
D000469:Alkaline Phosphatase / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000819:agonists / Q000378:metabolism*; D005679:G(M3) Ganglioside / Q000494:pharmacology / Q000502:physiology*; D005732:Gangliosides / Q000494:pharmacology / Q000502:physiology*; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology* / Q000378:metabolism; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011799:Quinazolines; D020032:Tyrphostins / Q000494:pharmacology
D005679:G(M3) Ganglioside; D005732:Gangliosides; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D020032:Tyrphostins; C021298:ganglioside, GD1a; C101044:RTKI cpd; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D000469:Alkaline Phosphatase