, Volume 38, Issue 4, pp 333-340
Date: 26 Jun 2007

Endosomal location of dopamine receptors in neuronal cell cytoplasm

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Abstract

Five subtypes of dopamine receptor exist in two subfamilies: two D1-like (D1 and D5) and three D2-like (D2, D3 and D4). We produced novel monoclonal antibodies against all three D2-like receptors and used them to localize receptors in Ntera-2 (NT-2) cells, the human neuronal precursor cell line. Most of the immunostaining for all three receptors colocalized with mannose-6-phosphate receptor, a marker for late endosomes formed by internalization of the plasma membrane. This result was obtained with antibodies against three different epitopes on the D3 receptor, to rule out the possibility of cross-reaction with another protein, and controls without primary antibody or in the presence of competitor antigen were completely negative. In rat cerebral cortex and hippocampus, some of the dopamine receptor staining was found in similar structures in neuronal cell cytoplasm. Only some of the neurons were positive for dopamine receptors and the pattern was consistent with previously-reported patterns of innervation by dopamine-producing neurons. Endosomal dopamine receptors may provide a useful method for identifying cell bodies of dopamine-responsive neurons to complement methods that detect only active receptors in the neuronal cell membrane.