Functional role of gangliotetraosylceramide in epithelial-to-mesenchymal transition process induced by hypoxia and by TGF-{beta}.
The epithelial-to-mesenchymal transition (EMT) is a basic cellular process that plays a key role in normal embryonic development and in cancer progression/metastasis. Our previous study indicated that EMT processes of mouse and human epithelial cells induced by TGF-β display clear reduction of gangliotetraosylceramide (Gg4) and ganglioside GM2, suggesting a close association of glycosphingolipids (GSLs) with EMT. In the present study, using normal murine mammary gland (NMuMG) cells, we found that levels of Gg4 and of mRNA for the UDP-Gal:β1-3galactosyltransferase-4 (β3GalT4) gene, responsible for reduction of Gg4, were reduced in EMT induced by hypoxia (∼1% O(2)) or CoCl(2) (hypoxia mimic), similarly to that for TGF-β-induced EMT. An increase in the Gg4 level by its exogenous addition or by transfection of the β3GalT4 gene inhibited the hypoxia-induced or TGF-β-induced EMT process, including changes in epithelial cell morphology, enhanced motility, and associated changes in epithelial vs. mesenchymal molecules. We also found that Gg4 is closely associated with E-cadherin and β-catenin. These results suggest that the β3GalT4 gene, responsible for Gg4 expression, is down-regulated in EMT; and Gg4 has a regulatory function in the EMT process in NMuMG cells, possibly through interaction with epithelial molecules important to maintain epithelial cell membrane organization.
Guan
Feng
F
Division of Biomembrane Research, Pacific Northwest Research Institute, Seattle, Washington 98122, USA.
Schaffer
Lana
L
Handa
Kazuko
K
Hakomori
Sen-Itiroh
SI
D000818:Animals; D015153:Blotting, Western; D015687:Cell Hypoxia / Q000502:physiology*; D002465:Cell Movement / Q000187:drug effects; D002478:Cells, Cultured; D003035:Cobalt / Q000494:pharmacology; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects* / Q000502:physiology; D005678:G(M2) Ganglioside / Q000378:metabolism; D005732:Gangliosides / Q000378:metabolism*; D047468:Immunoprecipitation; D008321:Mammary Glands, Animal / Q000166:cytology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
C011258:G(A1) ganglioside; D005732:Gangliosides; D016212:Transforming Growth Factor beta; D005678:G(M2) Ganglioside; D003035:Cobalt; C018021:cobaltous chloride