Membrane hyperpolarisation by Kir2 potassium channels drive protective microglial functions in Alzheimer’s disease

Introduction

Alzheimer’s disease (AD), the most prevalent form of dementia, is strongly shaped by microglial function. Genetic risk variants for late-onset AD are preferentially expressed in microglia, highlighting their central role in disease pathogenesis. In response to amyloid-β (Aβ) deposition, microglia undergo pronounced phenotypic changes and adopt specialized disease-associated states within the plaque microenvironment. These states are critically regulated by local cues, relying on TREM2-dependent signaling pathways that promote transcriptional programs supporting microglial metabolism, phagocytosis, proliferation and survival. While transcriptional signatures of reactive microglia in AD have been extensively characterized, the mechanisms by which these programs are translated into functional responses remain incompletely understood. In particular, the contribution of ion channels as key regulators of cellular electrical properties and intracellular signaling has received comparatively little attention.

Experimental approaches
To investigate the role of ion channels in microglial responses during amyloid pathology, we studied murine models of amyloidosis and human microglial xenografts. Microglia in close proximity to Aβ plaques were analysed using whole-cell patch-clamp electrophysiology to assess changes in membrane potential and ion channel activity. A combination of pharmacological manipulation, single-cell RNA sequencing and genetic deletion approaches was employed to identify a specific potassium channel subtype underlying the observed electrophysiological changes. Integration of these approaches allowed us to investigate the relationship between ion channel activity and disease-associated microglial states, as well as signaling pathways implicated in AD. In addition, histological, biochemical and transcriptomic analyses were used to assess the role of microglial Kir2 on amyloid pathology and inflammatory responses.

Results
Electrophysiological recordings revealed that plaque-associated microglia exhibit a strongly hyperpolarised membrane potential and prominent inwardly rectifying potassium currents compared to microglia located distant from plaques. This electrophysiological phenotype emerged upon microglial contact with Aβ deposits and was maintained across different stages of pathology. Transcriptomic and genetic analyses identified a specific inwardly rectifying potassium channel subtype of the Kir2 family as a major contributor to these changes in plaque-associated microglia. Functional studies further suggested that this channel is embedded within canonical disease-associated microglial states and is linked to signaling pathways known to regulate reactive microglia in AD. Modulation or loss of Kir2 resulted in marked alterations in amyloid burden, plaque architecture and inflammatory signatures, consistent with changes in microglial function.

Conclusion
Together, our findings identify membrane hyperpolarisation mediated by inwardly rectifying Kir2 potassium channels as a critical biophysical feature of reactive microglia during amyloid pathology, linking transcriptional microglial programs to functional responses in Alzheimer’s disease.