Work

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

Year: 2025

Type: preprint

Abstract: 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 (PIP 2 ), and is compromised in mouse models of cerebral small vessel (cSVD). Although decreased PIP 2 availability is a common feature of cSVD, mechanisms underlying PIP 2 synthesis remain poorly understood. We hypothesized that Arf6, a small GTPase expressed in cECs that stimulates PIP 2 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 in vivo . Exogenously provided PIP 2 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 PIP 2 levels and demonstrate that diminished PIP 2 synthesis is sufficient to impair functional hyperemia. Furthermore, we identify Arf6 as a mechanistic link between PIP 2 production and endothelial electrical signaling, highlighting Arf6 as a potential therapeutic target for restoring functional hyperemia. Significance Statement Active brain regions send electrical signals through capillaries to dilate upstream arterioles and increase blood flow. The resulting activity-dependent increase in local blood flow (functional hyperemia) is mediated through inward-rectifier potassium (Kir2.1) channels. These channels— and hence functional hyperemia—require continuous regeneration of the lipid cofactor PIP 2 (phosphatidylinositol-4,5-bisphosphate). If PIP 2 is deficient, electrical signaling fails—a defect characteristic of models of cerebral small vessel disease and Alzheimer’s disease. We identify the small GTPase Arf6 as a key to maintaining PIP 2 and thus preserving capillary Kir2.1 activity and functional hyperemia. Our findings reveal an important pathway for PIP 2 homeostasis and position Arf6 as a cornerstone upholding functional hyperemic responses, highlighting Arf6 as a target for restoring cerebral blood flow in disease.

Source: bioRxiv (Cold Spring Harbor Laboratory)

DOI: 10.64898/2025.12.23.696233