CREB Is Critically Implicated in Skin Mast Cell Degranulation Elicited via FcεRI and MRGPRX2

Area of Science:

• Immunology
• Dermatology
• Molecular Biology

Background:

• Skin mast cells (MCs) are key players in allergic reactions and chronic skin conditions like urticaria and dermatitis.
• The transcription factor cAMP response element binding protein (CREB) is known to maintain MC survival through a feedback loop with KIT.
• MC degranulation, the release of pre-stored mediators, is a critical function in acute allergic responses.

Purpose of the Study:

• To investigate the role of CREB in the expression and function of FcεRI and MRGPRX2, receptors essential for MC degranulation.
• To determine if CREB influences the synthesis and release of pre-formed mediators from skin MCs.

Main Methods:

• Pharmacological inhibition of CREB using CREBi (666-15).
• RNA interference (knockdown) to reduce CREB levels.
• Analysis of FcεRI and MRGPRX2 expression and function.
• Assessment of pre-formed mediator levels (tryptase, histamine, β-hexosaminidase).

Main Results:

• CREB inhibition/knockdown only slightly affected FcεRI and MRGPRX2 expression but strongly reduced KIT levels.
• MRGPRX2 surface expression increased with CREB knockdown, yet its degranulation function decreased.
• FcεRI function was more significantly impacted than its expression.
• Levels of pre-formed mediators (tryptase, histamine, β-hexosaminidase) remained unchanged, indicating CREB does not regulate granule synthesis.

Conclusions:

• CREB moderately influences FcεRI and MRGPRX2, but is essential for maintaining mast cell releasability and degranulation machinery, independent of stimulus.
• CREB is the first identified factor to oppositely regulate MRGPRX2 expression and function.
• CREB is vital for skin MC survival, proliferation, and secretory competence, playing a multifaceted role in mast cell biology.