The mitochondrial glutamate carrier 1 (GC1) was previously cloned from human brain cDNA and showed high levels of expression in the whole pancreas. According to the role that glutamate might play in ß cells as an additive factor in glucose stimulated insulin secretion, it was of interest to determine if GC1 was expressed in insulin secreting cell lines as well as primary cells and to assess whether GC1 suppression would affect glucose stimulated insulin secretion. In the course of this study, we have demonstrated GC1 expression in pancreatic ß cells. The downregulation of GC1 had little impact on mitochondrial proton gradient although it promoted a decrease in glucose evoked insulin secretion at stimulatory glucose concentration. This defect in the secretory response was restored upon provision of cell permeant methyl-glutamate. In conclusion, we have shown that GC1 is necessary for the full development of glucose induced insulin secretion, although the exact site for glutamate action is currently unknown. Further investigation should delineate the specific role of GC1 in insulin release.