Crosstalk between G-protein and Ca2+ pathways switches intracellular cAMP levels

Area of Science:

• Cellular signaling and molecular networks
• Systems biology and mathematical modeling
• Biochemistry of cyclic nucleotides

Background:

• Cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) are vital intracellular messengers.
• Their concentrations are tightly regulated by synthases (adenylate cyclase, guanylate cyclase) and phosphodiesterases.
• Existing models often overlook the distinct biochemical properties of different enzyme isoforms.

Purpose of the Study:

• To develop novel mathematical models of cAMP and cGMP regulatory networks, incorporating isoform-specific properties.
• To investigate the mechanisms of joint cAMP and cGMP regulation.
• To analyze the regulation of cilia beat frequency in Paramecium by calcium (Ca2+).

Main Methods:

• Systems biology approach to construct mathematical models of intracellular messenger networks.
• Inclusion of biochemical properties of different adenylate cyclase and guanylate cyclase isoforms.
• Application of models to study calcium-dependent regulation of cilia beat frequency in Paramecium.

Main Results:

• The diversity of isoform combinations explains the wide range of cellular processes dependent on these networks.
• Models reveal a new mechanism for the switching properties of G-protein subunits in nucleotide regulation.
• Calcium (Ca2+) can activate or inhibit adenylate cyclase in a concentration-dependent manner, explaining varied effects on cilia beat frequency.

Conclusions:

• Isoform diversity in cyclic nucleotide regulatory networks is key to cellular process variability.
• The developed models provide a mechanistic explanation for calcium's dual role in regulating adenylate cyclase activity.
• This framework elucidates the complex interplay of signaling molecules in cellular functions like cilia motility.