ELISA-Based Enzyme Kinetics Assay for Measuring cGAS Activity.

Area of Science:

• Immunology
• Biochemistry
• Molecular Biology

Background:

• Cyclic GMP-AMP synthase (cGAS) is a crucial cytosolic DNA sensor initiating innate immune responses.
• cGAS synthesizes 2'3'-cGAMP, a second messenger activating downstream signaling pathways with potential antitumor effects.
• Accurate measurement of cGAS enzymatic activity is vital for mechanistic and therapeutic studies.

Purpose of the Study:

• To develop a rapid and accessible ELISA-based protocol for quantifying 2'3'-cGAMP product formation.
• To enable derivation of cGAS enzymatic parameters using standard laboratory equipment.
• To offer a sensitive alternative to traditional, equipment-intensive kinetic assays.

Main Methods:

• Utilized a commercially available 2'3'-cGAMP ELISA kit for product quantification.
• Initiated cGAS reactions with defined DNA ligands and quenched at multiple time points.
• Calculated initial velocities from time course measurements to determine Michaelis-Menten parameters.

Main Results:

• Established an ELISA protocol for direct, product-specific quantification of 2'3'-cGAMP.
• Enabled determination of cGAS kinetic parameters including V0, Vmax, kcat, and k1/2.
• Achieved reproducible kinetic results within approximately 4 hours.

Conclusions:

• The developed ELISA protocol offers a sensitive and broadly applicable method for cGAS enzyme kinetics.
• This accessible approach allows researchers without advanced instrumentation to reliably measure cGAS activity.
• The protocol is suitable for evaluating modulators of cGAS activity and assessing kinetics with diverse substrates.