The MRGPRX2-substance P pathway regulates mast cell migration

Area of Science:

• Immunology
• Neuroscience
• Dermatology

Background:

• Mast cells (MCs) are immune cells that degranulate upon specific stimuli.
• The close proximity of MCs to nerves suggests a functional interaction, but the underlying mechanisms are not fully understood.
• MRGPRX2 is a receptor expressed on MCs, implicated in their activation.

Purpose of the Study:

• To investigate the expression patterns and functions of MRGPRX2 in human mast cells (hMCs).
• To elucidate the role of Substance P (SP) in regulating MRGPRX2 expression and MC behavior.
• To determine the significance of SP-MRGPRX2 signaling in MC positioning and communication with nerve fibers (NFs) in inflammatory skin conditions.

Main Methods:

• Analysis of MRGPRX2 expression in hMC progenitors and mature hMCs.
• Stimulation of hMCs with Substance P (SP) at varying concentrations.
• Assessment of MC degranulation and chemotaxis in response to SP.
• Evaluation of MRGPRX2+ MCs and their proximity to SP+ NFs in psoriatic skin samples and during in vitro skin reinnervation models.

Main Results:

• MRGPRX2 expression is heterogeneous in both hMC progenitors and mature hMCs.
• SP is a potent activator of MRGPRX2, with long-term SP supplementation expanding MRGPRX2-expressing cells.
• High SP concentrations induce rapid MC degranulation, while low concentrations promote chemotaxis of immature MCs.
• Increased numbers of MRGPRX2+ MCs are observed in inflammatory skin conditions like psoriasis.
• In vitro, MRGPRX2+ MCs preferentially localize near and migrate towards SP+ NFs, indicating directed migration.

Conclusions:

• SP-MRGPRX2 signaling is a key regulator of mast cell localization and migration within tissues.
• This signaling pathway facilitates communication between immune cells and nerve fibers, particularly in the context of skin inflammation.
• The findings highlight a novel mechanism for immune cell-nerve interaction mediated by SP and MRGPRX2.