Lateral Mobility and Internalization of Hormone Receptors to Human Chorionic Gonadotropin in Cultured Rat Granulosa Cells

Abstract

Since the introduction by Singer and Nicholson (1) of the concept of membrane fluidity and lateral mobility of membrane proteins, such mobility has been demonstrated for several membrane proteins, including receptors to immunoglobulins (2), lectins (3), catecholamines (4) and acetylcholine (5,6). Moreover, it was recently suggested that receptors on the plasma membrane can be internalized after binding specific ligands (7,8). In this study we have shown by high resolution autoradiography that clusters of receptor-bound human chorionic gonadotropin (hCG) are formed on the cell membrane of cultured granulosa cells, and that the bound hormone is subsequently internalized into lysosomes where degradation may occur. Lateral movement of receptor-bound hormone to form clusters, patches and caps following association with antibody to the hormone was demonstrated using the indirect immunofluorescence technique.