Expression of a glutamate transporter cDNA in human pancreatic islets

A number of neuron-specific molecules have been found to be also expressed in pancreatic islets. Some of them might play a major role in the pathogenesis of an autoimmune reaction against the insulin-secreting beta-cells resulting in beta-cell destruction and the manifestation of insulin-dependent diabetes mellitus (IDDM). In ongoing studies our goal was to determine the role of other neuron-specific molecules in beta-cells function and in insulitis. We cloned a L-glutamate transporter from a highly purified fraction of human islet cells. The expression of that specific mRNA was marked in various regions of the brain; weak expression was detected in human islet cells, while no expression in any other tissue was observed. Sequence analysis revealed identity to the transcripts isolated from human brain. The cloned novel cDNA from human islets encodes a key molecule of the excitatory neurotransmission pathway. The techniques used provide a model for the cloning and expression of molecules expressed both in endocrine and neuronal tissue. With characterization of its structure the possible role of the L-glutamate transporter as autoantigen in IDDM is now under investigation.