Implantation of hormone receptors: fusion of membrane components with cell membranes

Abstract

In the last few years considerable progress has been made in the study of receptor-response systems which are located on cell membranes. Yet the unravelling of the underlying mechanisms at the molecular level has been rather slow. Biochemical characterisation of the components required solubilisation of the membrane molecules in detergents, which resulted almost invariably in the loss of biological activity of the receptor-response system. Reconstitution of receptor activity was rarely obtained and reproducibility of such experiments was poor (Heidman and Changeux, 1978; Eimerl et al., 1980). It seemed that tenacious binding of detergents to components of the system was a major problem. Obviously, if even one component of a receptor-response system failed to function the entire reconstituted system would fail to produce the expected response. Another problem in reconstitution was to create conditions of concentration, polarity, etc., under which the solubilised components would associate properly to produce the functional complex. Thus, crude and purified preparations of receptors were obtained which demonstrated specific binding of antagonists or agonists but failed to demonstrate biological activity. The binding data obtained with such preparations are therefore difficult to evaluate. Several years ago, because of the difficulties described above, we developed a different experimental approach to the study of membrane receptors and other hydrophobic membrane molecules (Orly and Schramm, 1976).