Abstract
Previous work had demonstrated the coupling of a beta-adrenergic receptor on an erythrocyte with the adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] of a tissue culture cell when the two cells were fused by Sendai virus. The validity of this finding for animal tissues in general, for membrane preparations, and for peptide hormone receptors could hitherto not be assessed. Available fusion procedures worked efficiently only with certain intact cells from tissue culture and with erythrocytes. In the present work a membrane fusion method was developed that causes the transfer of the glucagon receptor from purified rat liver membranes to Friend erythroleukemia cells; even direct transfer to a membrane fraction prepared from Friend cells became feasible. It can therefore be concluded that a peptide hormone receptor in a normal tissue membrane has properties similar to those demonstrated for a beta-adrenergic receptor in an erythrocyte: it exists in the membrane as a dissociable independent unit that can readily couple with the adenylate cyclase of a foreign cell. The efficiency of the membrane fusion procedure is due to the combined action of polyethylene glycol, phospholipids, stearylamine, and ATP in a salt medium. The method promises to be applicable to membranes of various cells and tissues, and it can probably be used to analyze hormone receptors and adenylate cyclase systems in states of malfunction by transfer to their respective counterpart in a normal cell membrane. Studies in biochemical hybridization of membrane components need not be limited to hormone activation of adenylate cyclase. With the aid of the membrane fusion method, this approach could be applied to any dissociable multicomponent system in biological membranes.