Novel neuronal neurotransmitter-specific cell-surface molecules.

Neuronal cell-surface molecules are an important group of membrane structures which include neurotransmitter receptor proteins [ 1 , 21, neurotransmitter transporters [3, 41 and a heterogeneous group of proteins involved in neuronal development [ 5, 61 and in the formation and maintenance of synaptic contacts [7]. The use of antibodies has provided a successful approach to the identification and molecular and functional characterization of these markers (see [8] for example). Immunological strategies which have been used include: ( 1 ) immunohistochemistry using intact cells labelled with appropriate antibodies; (2) immunoaffinity purification of cell-surface markers from solubilized membranes; (3) immunoaffinity purification of cells expressing the cell-surface marker of interest; (4) antibody-dependent complement-mediated or antibody-ricin-mediated destruction of cells expressing cell-surface marker; and (5) antibodymediated blockade of cell-surface marker. Over the last few years it has been demonstrated that antibodies recognizing a variety of neurotransmitter biosynthetic enzymes { i.e. choline acetyltransferase (ChAT) [9, lo], glutamate decarboxylase (GAD) [ 10, 1 l l , tyrosine hydroxylase [lo], dopamine B-hydroxylase (DBH) [ 121 and tryptophan hydroxylase (TPH) [ 131) are capable of lysing, in the presence of complement, neurotransmitter-specific synaptosomal subpopulations (ie. cholinergic, GABAergic, dopaminergic, noradrenergic and serotonergic, respectively). Results obtained are summarized in Table 1. Specific immunolysis usually results in a reduction in high-affinity trans-