Monoclonal antibodies detect the conservation of muscarinic cholinergic receptor structure from Drosophila to human brain and detect possible structural homology with alpha 1-adrenergic receptors.

Abstract

Muscarinic cholinergic receptors isolated from Drosophila heads, rat and human brain, dog heart, and monkey ciliary muscle were examined for structural similarities/differences by utilizing isoelectric focusing, sodium dodecyl sulfate/polyacrylamide gel electrophoresis [SDS/PAGE] and monoclonal antibody crossreactivity. Muscarinic receptors were affinity labeled with [3H]propylbenzilylcholine mustard and subjected to isoelectric focusing. Muscarinic receptors from each species focused with an isoelectric point of 5.9. The same proteins all migrated with a MW of 80,000 daltons on SDS gels. Six hybridomas secreting monoclonal antibodies specific for muscarinic receptors were developed by using purified rat brain muscarinic receptors as the antigen. The 6 different monoclonal antibodies immunoprecipitated muscarinic receptors from all tissues and species tested, including human and Drosophila brains, with equal efficacy. Muscarinic receptors are highly conserved over a considerable evolutionary period. One of the 6 muscarinic receptor monoclonal antibodies also immunoprecipitated rat liver .alpha.1-adrenergic receptors. Out of 5 monoclonal antibodies raised against .alpha.1-receptors, 2 immunoprecipitated muscarinic receptors. Some degree of structural homology exists between muscarinic cholinergic receptors and .alpha.1-adrenergic receptors.