Endothelial Arf6 sustains capillary electrical signaling and cerebral blood flow through PIP ₂ regeneration and activation of Kir2.1 channels

Brain capillaries sense neural activity and direct blood flow to active regions-a process termed neurovascular coupling that underlies activity-dependent increases in local perfusion (functional hyperemia). A key contributor to functional hyperemic responses is the capillary endothelial cell (cEC) inward rectifier K⁺ (Kir2.1) channel, which is activated by neuronal activity-derived extracellular K⁺ and initiates vasodilatory electrical signals that propagate through the vascular network. Kir2.1 channel function requires continual production of its lipid cofactor, phosphatidylinositol-4,5-bisphosphate (PIP₂), and is compromised in mouse models of cerebral small vessel (cSVD). Although decreased PIP₂ availability is a common feature of cSVD, mechanisms underlying PIP₂ synthesis remain poorly understood. We hypothesized that Arf6, a small GTPase expressed in cECs that stimulates PIP₂ production, is critical for this process. Using patch-clamp electrophysiology, we demonstrate that inhibiting Arf6 activity progressively decreased cEC Kir2.1 channel activity. This deficit corresponded to loss of capillary-to-arteriole electrical signaling in isolated vessels and diminished functional hyperemia <i>in vivo</i>. Exogenously provided PIP₂ restored Kir2.1 currents and functional hyperemia after Arf6 inhibition or genetic knockdown. Collectively, our data indicate that cEC Arf6 sustains Kir2.1 activity by maintaining PIP₂ levels and demonstrate that diminished PIP₂ synthesis is sufficient to impair functional hyperemia. Furthermore, we identify Arf6 as a mechanistic link between PIP₂ production and endothelial electrical signaling, highlighting Arf6 as a potential therapeutic target for restoring functional hyperemia.