Fuc-GM1 ganglioside mimics the receptor function of GM1 for cholera toxin.
The ability of Fuc-GM1 ganglioside to mimic the receptor function of GM1 for cholera toxin (CT) has been investigated. For this purpose, rat glioma C6 cultured cells were enriched with Fuc-GM1 and the responsiveness to CT was compared with that of cells enriched with GM1 ganglioside. Fuc-GM1 was taken up by cells as rapidly and to the same extent as GM1. When comparable amounts of ganglioside were associated, the cells enriched with Fuc-GM1 bound the same amount of 125I-CT as did cells enriched with GM1. Under conditions in which GM1- and Fuc-GM1-enriched cells bound comparable amounts of CT, the Fuc-GM1-treated cells accumulated virtually the same amount of cyclic AMP as did GM1-treated cells, and activation of adenylate cyclase was also similar. The lag time preceding the CT-induced cAMP accumulation was the same in Fuc-GM1- and GM1-enriched cells. High-sensitivity isothermal titration calorimetry (ITC) experiments showed that the association constants of CT with Fuc-GM1 or GM1 ganglioside were comparable (4 x 10(7) M-1 and 1.9 x 10(7) M-1, respectively, at 25 degrees C). Also, the association constants of the B-subunit pentamer with Fuc-GM1 or GM1 ganglioside were comparable (about 3 x 10(7) M-1 and 7 x 10(7) M-1, respectively, at 25 degrees C).
Masserini
M
M
Department of Medical Chemistry and Biochemistry, University of Milano, Italy.
Freire
E
E
Palestini
P
P
Calappi
E
E
Tettamanti
G
G
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002151:Calorimetry; D002417:Cattle; D002470:Cell Survival; D002772:Cholera Toxin / Q000737:chemistry*; D000242:Cyclic AMP / Q000378:metabolism; D005677:G(M1) Ganglioside / Q000031:analogs & derivatives* / Q000737:chemistry / Q000502:physiology; D005910:Glioma / Q000737:chemistry; D007700:Kinetics; D051381:Rats; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic / Q000737:chemistry* / Q000502:physiology; D013552:Swine; D014316:Tritium; D014407:Tumor Cells, Cultured
D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; C034993:ganglioside receptor; D014316:Tritium; D005677:G(M1) Ganglioside; C039123:fucosyl GM1 ganglioside; D002772:Cholera Toxin; D000242:Cyclic AMP; D000262:Adenylyl Cyclases