Reversible activation of cellular factor XIII by calcium

Area of Science:

• Biochemistry
• Molecular Biology
• Hematology

Background:

• Factor XIII (FXIII) is a pro-transglutaminase crucial for blood coagulation.
• While plasma FXIII activation is well-understood, cellular FXIII activation and function remain less characterized.
• Cellular FXIII activation can occur non-proteolytically via conformational changes.

Purpose of the Study:

• To investigate the nature of calcium (Ca2+)-induced activation of Factor XIII (FXIII).
• To determine the reversibility and conditions influencing non-proteolytic FXIII activation.
• To develop a method distinguishing between zymogen and activated forms of FXIII.

Main Methods:

• Development of an analytical HPLC method to separate recombinant FXIII (rFXIII) from its activated form (rFXIIIa°).
• Evaluation of Ca2+ concentration, buffer, and salt effects on FXIII activation and deactivation.
• Assessment of thermal stress impact on freeze-dried rFXIII.

Main Results:

• Non-proteolytic FXIII activation and deactivation are significantly influenced by Ca2+ concentration, buffer, and salt.
• Ca2+-induced activation of rFXIII is fully reversible, with 2-5 mM CaCl2 maintaining full activity.
• Below 2 mM CaCl2, rFXIIIa° deactivates but can be reactivated; thermal stress creates a faster-activating FXIII form.

Conclusions:

• Non-proteolytic Factor XIII activation is a dynamic and reversible process controlled by specific ion concentrations and environmental factors.
• Understanding these activation dynamics is key to characterizing cellular FXIII function.
• Thermal history can alter FXIII's activation kinetics, suggesting potential implications for storage and handling.