IQGAP2 regulates blood-brain barrier immune dynamics

Area of Science:

• Neuroimmunology
• Cell Biology
• Molecular Biology

Background:

• Brain endothelial cells (BECs) maintain central nervous system (CNS) homeostasis via blood-brain barrier (BBB) functions.
• BECs normally limit leukocyte entry by expressing low adhesion receptor levels, but underlying molecular mechanisms are largely unknown.

Approach:

• Investigated the role of scaffold protein IQ motif containing GTPase activating protein 2 (IQGAP2) in regulating immune cell infiltration across the BBB.
• Utilized mouse and zebrafish models, single-cell RNA sequencing, and immunohistology.
• Analyzed human hippocampal tissue to assess IQGAP2 levels in Alzheimer's disease.

Key Points:

• Loss of Iqgap2 in mice and zebrafish led to increased peripheral leukocyte infiltration into the CNS under homeostatic and inflammatory conditions.
• Iqgap2-deficient BECs displayed a significant inflammatory signature, with upregulated adhesion receptors and antigen-processing machinery.
• Reduced hippocampal IQGAP2 was observed in human Alzheimer's disease tissues.

Conclusions:

• IQGAP2 is a critical regulator of BBB immune privilege.
• IQGAP2 controls immune cell entry into the CNS.
• Dysregulation of IQGAP2 may contribute to neuroinflammation and neurodegenerative diseases like Alzheimer's.