CHO Cells Lacking Expression Of The Conserved Oligomeric Golgi Complex Subunit 2 (Cog2) Show Reduced Sphingomyelin Content.

WALDO SPESSOTT; ANDREA ULIANA; HUGO J.F. MACCIONI

Ortona, Italia.

Workshop; FEBS Advanced Lecture Course “Lipid Signaling and Disease”.; 2009

Federation of European Biochemical Societies

The Conserved Oligomeric Golgi complex (COG) is a Golgi-associated tethering complex involved in retrograde trafficking of multiple Golgi enzymes. COG deficiencies lead to abnormal organization of the Golgi, defective trafficking of these enzymes and pleiotropic glycosylation defects in N-, O- and ceramide linked oligosaccharides. We studied the lipid synthesis status in Cog2 null mutant ldlC cells and found that in addition to defective sialylation of lactosylceramide, these cells also show defective synthesis of sphingomyelin (SM). Metabolic labeling experiments showed the synthesis of SM reduced to 25% in ldlC cells compared to wt cells. Sphingomyelin synthase (SMS) and GM3- synthase activities in vitro were essentially normal in ldlC cells. ldlC cells show SMS1 distributed throughout  the cytoplasm, contrasting with its typical Golgi localization in wt cells. Cog2  transfected ldlC cells recovered their SM synthesis capability and the SMS1 Golgi localization phenotype. Results indicate that Golgi misorganization caused by COG deficiency, in addition to affect glycosylation, also affects the synthesis of SM. Considering the importance of SM as a structural component of membranes, this finding is worth of consideration in relation to a possible contribution to the clinical phenotype of patients suffering congenital disorders of glycosylation type II.