Regulation of glycosyltransferases in ganglioside biosynthesis by phosphorylation and dephosphorylation

The biosynthesis of gangliosides is known to be under strict metabolic control. One level of control is through post-translational modification of the glycosyltransferases responsible for their biosynthesis. Thus, the activities of several sialyltransferases have been demonstrated to be downregulated by the action of protein kinase C (PKC) in cell-free and intact cell systems. This modulatory effect can be reversed at least in part by the action of membrane-bound phosphatases. In contrast, the activity of N-acetylgalactosaminyltransferase can be upregulated by the action of protein kinase A (PKA) in cultured cells. In addition, studies from several laboratories have demonstrated that phosphorylation of certain glycosyltransferases can affect their intracellular processing and translocation. Thus, modulation of glycosyltransferases by phosphorylation and dephosphorylation should represent an important regulatory mechanism for ganglioside biosynthesis.