PAK2-driven cytoskeleton-endosome dynamics control macrophage hyperphagia and SIRPA engagement

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• Macrophages exhibit cytoskeletal plasticity crucial for tissue homeostasis and immune responses.
• Tumor microenvironments reprogram macrophages, leading to diverse, often immunosuppressive, phenotypes.
• Modulating macrophage cytoskeletal dynamics offers therapeutic potential in cancer immunotherapy.

Purpose of the Study:

• To investigate the role of serine/threonine kinase PAK2 in regulating macrophage function.
• To determine if targeting PAK2 can reprogram macrophages for enhanced cancer cell killing.
• To explore the in vivo consequences of PAK2 inhibition on immune responses and tissue integrity.

Main Methods:

• Genetic manipulation to abolish PAK2 activity in macrophages.
• Assessment of macrophage membrane dynamics and phagocytic capacity.
• Analysis of endosomal receptor trafficking, including SIRPA recycling.
• In vivo studies examining PAK1/PAK2 cooperation in inflammation and malignancy models.

Main Results:

• Abolishing PAK2 activity induced significant membrane expansion and amplified engulfment of various targets.
• PAK2 was found essential for coordinating endosomal receptor trafficking, specifically SIRPA cell surface recycling.
• In vivo, PAK1 and PAK2 collaborate to limit oxidative stress and maintain gut barrier integrity.
• PAK2 inhibition promoted macrophage-driven hematologic malignancy in a low-grade inflammation context.

Conclusions:

• Targeting PAK2 transforms macrophage properties, enhancing their phagocytic and cancer-killing potential.
• PAK2 inhibition offers a promising immunotherapy strategy by leveraging hyperphagia and SIRPA sequestration.
• Understanding PAK2's role is critical for developing new cancer treatments that harness macrophage effector functions.