Posttranslational regulation of transporters

Posttranslational regulation of glutamate transporters includes changes in cell surface expression due to trafficking between the plasma membrane and intracellular compartments, and modulation of transport activity by direct phosphorylation, redox modulation of sulfhydryl groups and inhibition by arachidonic acid and other ci5-polyunsaturated fatty acids. 

Direct phosphorylation of the glutamate transporter proteins themselves has only been reported for GLT and GLAST. Protein kinase C phosphorylates GLAST and thereby reduces the transport activity to 25% with no change in cell surface expression (Conradt and Stoffel, 1997). GLT was originally reported to be stimulated by phosphorylation of serine-113 (Casado et al., 1993), but a recent report (Tan et al., 1999) suggests that the protein kinase-C-mediated stimulation represents an effect of the expression system used rather than an effect on GLT. Further studies are required to sort out the controversy. 

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