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Updated: Jun 17, 2026

Proteomics to Identify Proteins Interacting with P2X2 Ligand-Gated Cation Channels
Published on: May 18, 2009
Characterization of purinergic P2X4 receptor channels expressed in anterior pituitary cells
Hana Zemkova1, Marek Kucka, Shuo Li
1Section on Cellular Signaling, Program in Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4510, USA.
Abstract:
Anterior pituitary cells express cation-conducting P2X receptor channels (P2XRs), but their molecular identity, electrophysiological properties, cell-specific expression pattern, and physiological roles have been only partially characterized. In this study, we show by quantitative RT-PCR that mRNA transcripts for the P2X(4) subunit are the most abundant in rat anterior pituitary tissue and confirm the P2X(4)R protein expression by Western blot analysis. Single-cell patch-clamp recordings show that extracellular ATP induced an inward depolarizing current in a majority of thyrotropin-releasing hormone-responsive pituitary cells, which resembled the current profile generated by recombinant P2X(4)R. The channels were activated and desensitized in a dose-dependent manner and deactivated rapidly. Activation of these channels led to stimulation of electrical activity and promotion of voltage-gated and voltage-insensitive Ca(2+) influx. In the presence of ivermectin, a specific allosteric modulator of P2X(4)Rs, there was an approximately fourfold increase in the maximum amplitude of the ATP-induced inward current, accompanied by an increase in the sensitivity of receptors for ATP, slowed deactivation of receptors, and enhanced ATP-induced prolactin release. These results indicate that thyrotropin-releasing hormone-responsive cells, including lactotrophs, express homomeric and/or heteromeric P2X(4)Rs, which facilitate Ca(2+) influx and hormone secretion.
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