Cog2 null mutant CHO cells show defective sphingomyelin synthesis.

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

JOURNAL OF BIOLOGICAL CHEMISTRY

AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Año: 2010 vol. 285 p. 41472 - 41482

0021-9258

The COG (conserved oligomeric Golgi complex) is aGolgi-associated tethering complex involved in retrogradetrafficking of multiple Golgi enzymes. COG deficiencieslead to misorganization of the Golgi, defective trafficking ofglycosylation enzymes, and abnormal N-, O- and ceramidelinkedoligosaccharides. Here, we show that in Cog2 nullmutant ldlC cells, the content of sphingomyelin (SM) is reducedto
25% of WT cells. Sphingomyelin synthase (SMS)activity is essentially normal in ldlC cells, but in contrastwith the typical Golgi localization in WT cells, in ldlC cells,transfected SMS1 localizes to vesicular structures scatteredthroughout the cytoplasm, which show almost no signal ofco-transfected ceramide transfer protein (CERT). Cog2transfection restores SM formation and the typical SMS1Golgi localization phenotype. Adding exogenous N-6-[(7-nitrobenzo-2-oxa-1,3-diazol-4-yl)amino]hexanoyl-4-derythro-sphingosine (C6-NBD-ceramide) to ldlC cell culturesresults in normal SM formation. Endogenousceramide levels were 3-fold higher in ldlC cells than in WTcells, indicating that Golgi misorganization caused by Cog2deficiency affects the delivery of ceramide to sites of SMsynthesis by SMS1. Considering the importance of SM as astructural component of membranes, this finding is alsoworth of consideration in relation to a possible contributionto the clinical phenotype of patients suffering congenitaldisorders of glycosylation type II.