Glycosyltransferase complexes improve glycolipid synthesis.
The synthesis of gangliosides GM3 and GD3 is carried out by the successive addition of sialic acid residues on lactosylceramide (LacCer) by the Golgi located sialyltransferases Sial-T1 and Sial-T2, respectively. CHO-K1 cells lack Sial-T2 and only express GM3. Here we show that the activity of Sial-T1 was near 2.5-fold higher in homogenates of CHO-K1 cells transfected to express Sial-T2 (CHO-K1(Sial-T2)) than in untransfected cells. The appearance of Sial-T1 enzyme or gene transcription activators or the stabilization of the Sial-T1 protein were discarded as possible causes of the activation. Sial-T2 lacking the catalytic domain failed to promote Sial-T1 activation. Since Gal-T1, Sial-T1 and Sial-T2 form a multienzyme complex, we propose that transformation of formed GM3 into GD3 and GT3 by Sial-T2 in the complex leaves Sial-T1 unoccupied, enabled for new rounds of LacCer utilization, which results in its apparent activation.
Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC, UNC-CONICET), Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000 HUA Córdoba, Argentina.
Waldo
W
Spessott
Pilar M
PM
Crespo
José Luis
JL
Daniotti
Hugo J F
HJ
Maccioni
D000818:Animals; D015703:Antigens, CD / Q000737:chemistry*; D016466:CHO Cells; D020134:Catalytic Domain; D006224:Cricetinae; D003412:Cricetulus; D005679:G(M3) Ganglioside / Q000737:chemistry*; D005732:Gangliosides / Q000737:chemistry*; D006017:Glycolipids / Q000737:chemistry*; D006031:Glycosylation; D016695:Glycosyltransferases / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism; D007790:Lactosylceramides / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D015703:Antigens, CD; D005679:G(M3) Ganglioside; D005732:Gangliosides; D006017:Glycolipids; D007790:Lactosylceramides; C009744:CDw17 antigen; C026226:ganglioside, GD3; D016695:Glycosyltransferases