Intracellular signalling by nucleotide receptors in PC12 pheochromocytoma cells

✍ Scribed by Sandeep Raha; Lynne R. De Souza; Juta K. Reed

• Book ID: 102882746
• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 877 KB
• Volume: 154
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041540322

✦ Synopsis

Abstract

The effect of extracellular ATP was studied in PC12 cells, a neurosecretory line that releases ATP. The addition of micromolar concentrations of ATP to PC12 cells evoked a transient increase in the cytosolic free Ca^2+^ concentration ([Ca^2+^]~i~), as measured with the Ca^2+^‐dye fura 2. AMP and adenosine were without effect, ruling out the involvement of P~1~ receptors in mediating this response. The increase in [Ca^2+^]~i~ was reduced in calcium‐free media and virtually eliminated by the addition of EGTA, suggesting that calcium influx was the primary response initiated by extracellular ATP. Nucleotide triphosphates such as UTP and, to a lesser degree, ITP also evoked an increase in [Ca^2+^]~i~ while GTP and CTP had little effect. In order to identify the receptor subtype mediating this response, the efficacy of ATP and ATP cogeners was assessed. The rank order potency was ATP > adenosine 5′‐[γ‐thio]triphosphate > ADP > 2‐methylthioadenosine triphosphate (2‐MeSATP) ∼ adenosine 5′‐[β‐thio]diphosphate ≫ adenosine 5′‐[αβ‐methylene] triphosphate, adenosine 5′‐[βγ‐imido]triphosphate. This profile is not characteristic of either the P~2X~ or the conventional P~2Y~ receptors. The Ca^2+^ response exhibited desensitization to ATP that was dependent on the extracellular metabolism of ATP. UTP was equally effective in desensitizing the response. ATP, UTP, ITP, and to a much lesser extent 2MeSATP increased inositol phosphate production in a dose‐dependent manner, suggesting receptor coupling to phosphatidylinositol‐specific phospholipase C. These data are consistent with the view that PC12 cells express a class of non‐P~2Y~ nucleotide receptors (P~2N~) that mediate calcium influx and the accumulation of inositol phosphates. © 1993 Wiley‐Liss, Inc.