G proteins regulate dihydropyridine binding to moss plasma membranes

Area of Science:

• Plant Biology
• Cell Signaling
• Molecular Biology

Background:

• Calcium ions (Ca2+) are vital intracellular messengers regulating numerous biological processes.
• In Physcomitrella patens, calcium signaling is implicated in hormone-induced bud formation.
• Plasma membrane 1,4-dihydropyridine (DHP)-sensitive calcium channels are involved in cellular calcium level changes.

Purpose of the Study:

• To investigate the role of GTP-binding regulatory proteins (G proteins) in regulating moss calcium channels.
• To elucidate the mechanism by which G proteins influence DHP-sensitive calcium channel activity.

Main Methods:

• Utilized radioligand binding assays with [3H]azidopine to measure DHP binding to moss plasma membranes.
• Employed non-hydrolyzable GTP analog (GTPγS) to activate G proteins and GDP analog (GDPβS) to inactivate them.
• Assessed the effect of G protein activation/inactivation on the binding kinetics (association and dissociation) of DHP ligands.

Main Results:

• G protein activation with GTPγS significantly stimulated DHP binding to high-affinity receptors in moss plasma membranes.
• G proteins modulated the rates of [3H]azidopine association and dissociation, indicating regulation of channel kinetics.
• G protein inactivation with GDPβS did not alter the dose-dependent binding of DHP agonists or antagonists.

Conclusions:

• G proteins play a regulatory role in controlling the activity of plasma membrane calcium channels in Physcomitrella patens.
• G protein-mediated regulation likely occurs through a membrane-delimited pathway.
• These findings contribute to understanding calcium channel regulation in plants and its role in developmental processes.