Proteins Associated with α1‐Subunit‐Containing GABAA Receptors from Bovine Brain

In contrast to some other ion channels, there are at present no proteins known that bind specifically to mature GABAA receptor channels. Such proteins may be important for the structural organization and cytoskeletal anchoring of GABAA receptors and could also be expected to have channel modulatory effects. To identify proteins that are associated with naturally occurring GABAA receptors we immunoprecipitated these receptors from detergent-solubilized bovine brain membranes by an antibody directed against the alpha 1-subunit. Tubulin and actin were observed to coprecipitate specifically with the receptors. Nine additional proteins were detected, hinting at a complex protein network associated with alpha 1-subunit-containing GABAA receptors. Results of a biochemical characterization of these GABAA receptor-tubulin complex-associated proteins (GTAPs) are presented here. Peptide mass fingerprinting analysis and microsequencing of tryptic peptides indicated that at least three GTAPs have not been described until the present.