P2X₁and P2X₅Subunits Form the Functional P2X Receptor in Mouse Cortical Astrocytes

Abstract

ATP plays an important role in signal transduction between neuronal and glial circuits and within glial networks. Here we describe currents activated by ATP in astrocytes acutely isolated from cortical brain slices by non-enzymatic mechanical dissociation. Brain slices were prepared from transgenic mice that express enhanced green fluorescent protein under the control of the human glial fibrillary acidic protein promoter. Astrocytes were studied by whole-cell voltage clamp. Exogenous ATP evoked inward currents in 75 of 81 astrocytes. In the majority (ϳ65%) of cells, ATP-induced responses comprising a fast and delayed component; in the remaining subpopulation of astrocytes, ATP triggered a smoother response with rapid peak and slowly decaying plateau phase. The fast component of the response was sensitive to low concentrations of ATP (with EC 50 of ϳ40 nM). All ATP-induced currents were blocked by pyridoxal-phosphate-6-azophenyl-2Ј,4Ј-disulfonate (PPADS); they were insensitive to ivermectin. Quantitative real-time PCR demonstrated strong expression of P2X 1 and P2X 5 receptor subunits and some expression of P2X 2 subunit mRNAs. The main properties of the ATP-induced response in cortical astrocytes (high sensitivity to ATP, biphasic kinetics, and sensitivity to PPADS) were very similar to those reported for P2X 1/5 heteromeric receptors studied previously in heterologous expression systems.

P2X7 Nucleotide Receptor is Coupled to GSK-3 Inhibition and Neuroprotection in Cerebellar Granule Neurons

“…We have used the non-selective antagonist PPADS, together with the most selective antagonists currently available, BBG and A-438079 (Jiang et al 2000;Donnelly-Roberts and Jarvis 2007). Nevertheless, in the light of recent reports providing convincing evidences of new functional heteromers (Nicke et al 2005;Guo et al 2007;Lalo et al 2008) the existence of a heteromeric receptor formed by P2X 7 and any other subunit present in granule neurons cannot be excluded. Fig.…”

Astroglial calcium signalling in Alzheimer's disease

“…Calcium ions are the most ubiquitous and evolutionary ancient intracellular second messenger that controls various vital cellular functions and regulate physiological responses in virtually every living organism [36][37][38][39][40] [45][46][47]), transient receptor potential (TRP) channels [48,49] and sodium calcium exchanger (NCX), operating in the reverse mode [50]. The TRPC-containing channels [51] also contribute to the store-operated Ca 2+ entry initiated by the depletion of the ER store of releasable Ca 2+ [52,53].…”

P2X2 and P2X5 Subunits Define a New Heteromeric Receptor with P2X7-Like Properties

“…The P2X2/3 receptor was initially identified in sensory neurons through its unique pharmacological and biophysical profiles, which were recapitulated in a recombinant system (Lewis et al, 1995;Radford et al, 1997). Similarly, in submucosal arterioles and cortical astrocytes, ATPinduced currents display the same biophysical and pharmacological profiles that are observed in HEK cells cotransfected with P2X1 and P2X5 subunits (Haines et al, 1999;Lê et al, 1999;Surprenant et al, 2000;Lalo et al, 2008).…”