Purinergic P2Y1 Receptors Control Rapid Expression of Plasma Membrane Processes in Hippocampal Astrocytes

Abstract

Astrocytes regulate neuronal activity and blood brain barrier through tiny plasma membrane branches or astrocytic processes (APs) making contact with synapses and brain vessels. Several transmitters released by astrocytes and exerting their action on several receptor classes expressed by astrocytes themselves influence their physiology. Here we found that APs are dynamically modulated by purines. In live imaging experiments carried out in rat hippocampal astrocytes, Gq-coupled P2Y1 receptor blockade with the selective antagonist MRS2179 (1 μM) or inhibition of its effector phospholipase C using U73122 (3 μM) produced APs retraction, while stimulation of the same receptor with the selective agonist 2MeSADP (100 μM) increased their number. Since astrocytes, among other transmitters, release ATP by several mechanisms including connexin hemichannels, we used the connexin hemichannel inhibitor carbenoxolone (100 μM) and APs retraction was observed. In our system we then measured expression or function of channels important for modulation of volume transmission and K+ buffering, aquaporin-4, and K+ inward rectifying (Kir) channels, respectively. Aquaporin-4 expression level did not change whereas, in whole-cell patch-clamp recordings performed to measure Kir current, we observed an increase in K+ current in all conditions where APs number was reduced. These data are supporting the idea of a dynamic modulation of astrocytic processes by purinergic signal, strengthening the role of purines in brain homeostasis.

Glial Purinergic Signaling in Neurodegeneration

“…Functionally, the P2Y1 receptor signaling pathway is one of the major purinergic signaling pathways that may contribute to altered astrocyte properties in neurodegeneration, especially in AD. P2Y1 mediates calcium waves in astrocytes, which are linked to gliotransmitter release and synchronization of astrocytic syncytium, which is critical for synaptic plasticity (149)(150)(151). Unlike in the transcriptomic studies we summarized here, previous studies showed that astrocytic P2Y1 receptor expression is elevated in AD mouse models and human AD brain, especially in close vicinity to amyloid plaques (151,152).…”

Gene expression, proteome and calcium signaling alterations in immortalized hippocampal astrocytes from an Alzheimer’s disease mouse model

“…Potassium buffering by inwardly rectifying K + (Kir) channels during neuronal activity is fundamental to maintain adequate synaptic transmission and neuronal excitability 24 . We have previously shown that Kir channels are functionally expressed in primary hippocampal astrocytes 25 . Therefore, we performed patch-clamp experiments in WT-iAstro#2 and 3Tg-iAstro#2 lines.…”

Astrocytes promote ethanol-induced enhancement of intracellular Ca2+ signals through intercellular communication with neurons

“…4D) and adenylyl cyclase-sensitive responses (SQ22536, Figure 4D) (Caruso et al, 2012) showed comparable ability to depress calcium waveform amplitudes by roughly half and equivalent statistical significance in limiting the generation of SE astrocytes (Table S1). The efficiency of U73122 in inhibition of the PLC pathway was verified using an inactive analogue in parallel experiments (U73343: Figure S3) (Chisari et al, 2017). The inhibition effect of U73122 lends further credence to the impact of PLC pathways on astrocyte responsiveness.…”