Luteinizing hormone receptors are self-associated in slowly diffusing complexes during receptor desensitization.

Area of Science:

• Molecular Endocrinology
• Cellular Biology
• Receptor Dynamics

Background:

• Luteinizing hormone receptors (LHRs) are G protein-coupled receptors involved in reproductive function.
• Hormone binding to LHRs can lead to receptor desensitization, a process that reduces cellular response.
• Previous studies indicated that LHRs occupied by human chorionic gonadotropin (hCG) exhibit slow diffusion and self-association.

Purpose of the Study:

• To investigate if LHRs self-associate and form slowly diffusing structures upon hormone binding.
• To determine if LHRs retain this organization during the desensitized state.
• To understand the relationship between LHR organization and receptor responsiveness.

Main Methods:

• Utilized fluorescent photobleaching recovery (FPR) to assess lateral diffusion of GFP-tagged LHRs.
• Employed fluorescence energy transfer (FET) to measure self-association between GFP- and YFP-tagged LHRs.
• Induced receptor desensitization using hCG and monitored LHR behavior and cAMP levels.

Main Results:

• Wild-type LHRs showed fast lateral diffusion before hormone exposure.
• After hCG-induced desensitization, LHRs exhibited slow lateral diffusion, immobility, and self-association into visible clusters.
• Receptor responsiveness was restored only after the dissipation of these self-associated structures.

Conclusions:

• Desensitized LHRs form large, slowly diffusing, self-associated structures on the plasma membrane.
• Receptor desensitization is linked to the formation of these organized LHR structures.
• Dissipation of these structures is a prerequisite for LHRs to regain sensitivity to hormone binding.