Defective GM3 Synthesis in Cog2 Null Mutant CHO Cells Associates to Mislocalization of Lactosylceramide Sialyltransferase in the Golgi Complex |
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Authors: | Spessott Waldo Uliana Andrea Maccioni Hugo J F |
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Institution: | 1.Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC (UNC-CONICET), Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre s/n—Pabellón Argentina Ala Oeste, 5000, Córdoba, Argentina ; |
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Abstract: | The conserved oligomeric Golgi (COG) complex is a eight subunit (COG1 to 8) tethering complex involved in the retrograde trafficking
of multiple Golgi processing proteins. Here we studied the glycolipid synthesis status in ldlC cells, a Cog2 null mutant CHO
cell line. Biochemical studies revealed a block in the coupling between LacCer and GM3 synthesis, resulting in decreased levels
of GM3 in these cells. Uncoupling was not attributable to decreased activity of the glycosyltransferase that uses LacCer as
acceptor substrate (SialT1). Rather, immunocytochemical experiments evidenced a mislocalization of SialT1 as consequence of
the lack of Cog2 in these cells. Co-immunoprecipitation experiments disclose a Cog2 mediated interaction of SialT1 with the
COG complex member Cog1. Results indicate that cycling of some Golgi glycolipid glycosyltransferases depends on the participation
of the COG complex and that deficiencies in COG complex subunits, by altering their traffic and localization, affect glycolipid
composition. |
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