Phosphorylation of iRhom2 at the plasma membrane controls mammalian TACE-dependent inflammatory and growth factor...

Area of Science:

• Cell Biology
• Molecular Biology
• Immunology

Background:

• Proteolytic cleavage of cell surface ligands regulates intercellular signaling.
• TACE (TNFα-converting enzyme) sheds inflammatory cytokines like TNFα and EGF receptor ligands.
• iRhoms control TACE transport and maturation but their precise role in TACE activation is unclear.

Purpose of the Study:

• To elucidate the role of iRhom2 in the regulation of TACE activity and shedding.
• To investigate the molecular mechanism by which iRhom2 controls TACE function at the cell surface.
• To determine the physiological relevance of the iRhom2-TACE interaction in inflammatory responses.

Main Methods:

• Co-immunoprecipitation to assess iRhom2-TACE association throughout the secretory pathway.
• Analysis of TACE shedding and activity in cells expressing wild-type and mutant iRhom2.
• Phosphorylation site mapping and 14-3-3 binding assays.
• In vivo studies using primary mouse macrophages to assess inflammatory responses.

Main Results:

• iRhom2 remains associated with TACE from the ER to the cell surface, stabilizing mature TACE.
• ERK1/2-mediated phosphorylation of iRhom2's N-terminus and subsequent 14-3-3 binding license TACE proteolytic activity at the plasma membrane.
• This iRhom2-dependent TACE activation mechanism triggers inflammatory responses in macrophages.

Conclusions:

• iRhom2 acts as a crucial regulator of TACE by binding to it throughout its lifecycle.
• Post-translational modifications of iRhom2, including phosphorylation, are critical for licensing TACE shedding activity.
• The iRhom2-TACE axis represents a key pathway controlling stimulated cytokine and growth factor signaling, impacting inflammatory processes.