P21-activated kinase 2 is essential in maintenance of peripheral Foxp3⁺ regulatory T cells

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• P21-activated kinase 2 (Pak2) is a key effector of Rho GTPases, regulating T cell functions.
• Previous studies established Pak2's role in T cell development within the thymus, including regulatory T (Treg) cells.
• The function of Pak2 in peripheral T cell subsets, particularly CD4+ T cells and Foxp3+ Treg cells, remains unclear.

Purpose of the Study:

• To investigate the role of Pak2 in the function and maintenance of peripheral CD4+ T cells.
• To determine if Pak2 is essential for the homeostasis and function of Foxp3+ Treg cells in the periphery.

Main Methods:

• Generation of inducible Pak2 knockout (KO) mice for acute deletion in CD4+ T cells via tamoxifen administration.
• Analysis of T cell populations, including naive CD4+ T cells and Foxp3+ Treg cells, following Pak2 deletion.
• Assessment of Treg cell proliferation, Foxp3 expression, and in vitro differentiation upon T cell receptor and IL-2 stimulation.

Main Results:

• Temporal deletion of Pak2 significantly reduced the number of peripheral Foxp3+ Treg cells.
• Pak2 deficiency minimally impacted the homeostasis of naive CD4+ T cells.
• Pak2 was essential for Treg cell proliferation and Foxp3 expression following stimulation, as well as for in vitro induced Treg cell differentiation and naive CD4+ T cell activation.

Conclusions:

• Pak2 is indispensable for maintaining the peripheral Treg cell pool.
• Pak2 provides critical proliferation and maintenance signals for Foxp3+ Treg cells.
• Pak2 plays a vital role in regulating the function of peripheral CD4+ T cells, particularly Treg cells.