Modulation of cellular transglutaminase: protease-induced activation

Area of Science:

• Biochemistry
• Cell Biology
• Enzymology

Background:

• Transglutaminase enzymes are crucial for cellular processes and are found in various molecular forms.
• Understanding the distribution and regulation of transglutaminase forms is essential for comprehending cellular functions.

Purpose of the Study:

• To investigate the different molecular forms of transglutaminase present in various cell types.
• To explore the activation mechanisms and modulation of transglutaminase activity during cellular differentiation.

Main Methods:

• Analysis of enzyme activity and molecular weight in different cellular fractions.
• Enzyme activation studies using proteases and sulfhydryl compounds post-cell lysis.
• Examination of transglutaminase modulation in cells undergoing terminal differentiation.

Main Results:

• Identified a 95 K dalton transglutaminase associated with membrane fractions and a 50 K dalton form in epidermis and hair follicles.
• Protease treatment increased transglutaminase activity, revealing distinct enzyme forms (95 K and 50 K daltons) in activated rat chondrosarcoma, mouse epidermal, and rabbit endometrial cells.
• The 95 K dalton enzyme, unlike the 80 K dalton form, can be activated by proteases or sulfhydryl compounds after cell lysis.
• Transglutaminase forms are modulated in terminally differentiating cells, including reticulocytes, megakaryocytes, monocytes, chondrocytes, and epidermal cells.

Conclusions:

• Cellular differentiation involves modulation of transglutaminase forms, suggesting a role in terminal differentiation processes.
• Post-translational modifications are likely responsible for altered transglutaminase catalytic activity during differentiation.