Cell swelling enhances ligand-driven β-adrenergic signaling.

Area of Science:

• Cellular Biophysics
• Molecular Pharmacology
• Membrane Biology

Background:

• G protein-coupled receptors (GPCRs) are crucial cell surface proteins whose function is influenced by their membrane environment.
• The conformational state of GPCRs dictates their activity and downstream signaling.
• Microscopic interactions within the plasma membrane play a significant role in modulating GPCR behavior.

Purpose of the Study:

• To investigate the impact of osmotic swelling on GPCR conformation and function.
• To determine if osmotic swelling alters the biophysical context of receptors within intact cells.
• To assess the downstream signaling consequences of altered receptor conformation due to osmotic swelling.

Main Methods:

• Utilized osmotic swelling as a pleiotropic stimulus in intact cells.
• Monitored the functional response of the β2-adrenergic receptor (a prototypical GPCR).
• Measured downstream signaling, specifically cAMP production, in response to adrenergic stimulation.
• Validated findings in primary cell types, including adult cardiomyocytes.

Main Results:

• Osmotically swollen cells promote an active conformation of the β2-adrenergic receptor.
• Adrenergic stimulation in swollen cells resulted in significantly increased amplitude of cAMP transient responses.
• The observed potentiation of signaling was validated in primary cell types like adult cardiomyocytes.
• Evidence suggests this mechanism is not limited to the β2-adrenergic receptor.

Conclusions:

• Receptor function is finely modulated by the biophysical context of the cell membrane.
• Osmotic swelling acts as a potentiator of GPCR-mediated downstream signaling.
• This suggests a general regulatory mechanism where cellular biophysical changes influence receptor activity and signaling outcomes.