Nucleotide-mediated calcium signaling in rat cortical astrocytes: Role of P2X and P2Y receptors.
ATP is the dominant messenger for astrocyte-to-astrocyte calcium-mediated communication. Definition of the exact ATP/P2 receptors in astrocytes and of their coupling to intracellular calcium ([Ca(2+)](i)) has important implications for brain physiology and pathology. We show that, with the only exception of the P2X(6) receptor, primary rat cortical astrocytes express all cloned ligand-gated P2X (i.e., P2X(1-5) and P2X(7)) and G-protein-coupled P2Y receptors (i.e., P2Y(1), P2Y(2), P2Y(4), P2Y(6), and P2Y(12)). These cells also express the P2Y-like UDP-glucose receptor, which has been recently recognized as the P2Y(14) receptor. Single-cell image analysis showed that only some of these receptors are coupled to [Ca(2+)](i). While ATP induced rapid and transient [Ca(2+)](i) increases (counteracted by the P2 antagonists suramin, pyridoxal-phosphate-6-azophenyl-2'-4'-disulfonic acid and oxidized ATP), the P2X(1)/P2X(3) agonist alphabetameATP produced no changes. Conversely, the P2X(7) agonist BzATP markedly increased [Ca(2+)](i); the presence and function of the P2X(7) receptor was also confirmed by the formation of the P2X(7) pore. ADP and 2meSADP also produced [Ca(2+)](i) increases antagonized by the P2Y(1) antagonist MRS2179. Some cells also responded to UTP but not to UDP. Significant responses to sugar-nucleotides were also detected, which represents the first functional response reported for the putative P2Y(14) receptor in a native system. Based on agonist preference of known P2 receptors, we conclude that, in rat astrocytes, ATP-induced calcium rises are at least mediated by P2X(7) and P2Y(1) receptors; additional receptors (i.e., P2X(2), P2X(4), P2X(5), P2Y(2), P2Y(4), and P2Y(14)) may also contribute.
Fumagalli
Marta
M
Department of Pharmacological Sciences, University of Milan, Milan, Italy.
Brambilla
Roberta
R
D'Ambrosi
Nadia
N
Volonté
Cinzia
C
Matteoli
Michela
M
Verderio
Claudia
C
Abbracchio
Maria P
MP
D000244:Adenosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000819:agonists / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000235:genetics*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism*; D006706:Homeostasis / Q000187:drug effects / Q000235:genetics; D009711:Nucleotides / Q000378:metabolism*; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D058469:Receptors, Purinergic P2X; D058472:Receptors, Purinergic P2Y1
C111914:N(6)-methyl-2'-deoxyadenosine 3',5'-diphosphate; D009711:Nucleotides; C546384:P2ry1 protein, rat; D043562:Receptors, G-Protein-Coupled; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D058472:Receptors, Purinergic P2Y1; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate