Co-expression of PADI isoforms during progenitor differentiation enables functional diversity

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Protein isoforms generated through alternative splicing or promoter usage play crucial roles in tissue function.
• The peptidylarginine deiminase (PAD) family, particularly PAD2 and PAD3, are involved in various cellular processes.
• Understanding isoform-specific functions is essential for comprehending complex biological mechanisms.

Purpose of the Study:

• To characterize the expression and function of predicted PADI3 isoforms (PADI3α and PADI3β) in hair follicles.
• To identify and describe the expression of a novel PADI2 isoform (PADI2β) in the oligodendrocyte lineage.
• To elucidate the functional interplay between PADI2 isoforms and PADI3 isoforms in their respective cellular contexts.

Main Methods:

• Analysis of gene expression patterns for PADI2 and PADI3 isoforms in specific cell types (oligodendrocytes and hair follicles).
• In vitro expression studies to assess protein localization, stability, and enzymatic activity of PADI3α and PADI3β.
• Investigation of protein-protein interactions and their impact on enzymatic function, specifically focusing on PADI3β's effect on PADI3α.

Main Results:

• A novel PADI2 isoform, PADI2β, was identified in oligodendrocytes, originating from an intronic promoter and inhibiting differentiation.
• PADI3α and PADI3β isoforms were localized to developing hair follicles, with expression increasing during differentiation.
• PADI3β exhibits low protein stability and lacks citrullination activity but modulates PADI3α's activity and stability through heterodimerization.

Conclusions:

• The study establishes the expression and distinct functions of PADI2 and PADI3 isoforms, highlighting their opposing roles in oligodendrocyte differentiation and hair follicle development.
• PADI2 isoforms (PADI2α and PADI2β) exert opposing effects on oligodendrocyte lineage progression.
• PADI3β likely regulates PADI3α activity via direct binding and heterodimer formation, expanding the understanding of citrullination regulation in complex tissues.