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Calcium Signaling Mediated by Aminergic GPCRs Is Impaired by the PI3K Inhibitor LY294002 and Its Analog LY303511 in a PI3K-independent Manner

The phosphoinositide 3-kinase (PI3K) inhibitor LY294002 (LY294) and its much less active analog LY303511 (LY303) constitute the paired probe that is commonly used to demonstrate the involvement of PI3K in intracellular signaling. We studied effects of LY294 and LY303 on Ca2+ signaling initiated by certain GPCR agonists in cells of several lines, including CHO cells expressing the recombinant serotonin receptor 5-HT2C and mesenchymal stromal cells derived from the human adipose tissue (AD-MSCs) and umbilical cord (UD-MSCs). The LY294/LY303 pair exerted apparently specific effects on responsiveness of AD-MSCs to ATP, suggesting the involvement of PI3K in ATP transduction. Surprisingly, LY303 inhibited Ca2+ transients elicited by histamine in the same cells, while LY294 was ineffective. This observation and other findings implicated a PI3K-unrelated mechanism in mediating effects of the LY compound on AD-MSC responsiveness to histamine. With LY303 in the bath, the dose dependence of histamine responses was shifted positively at the invariable number of responsive cells, as would be the case with a competitive antagonist of histamine receptors. Moreover, LY303 and LY294 inhibited Ca2+ transients elicited by acetylcholine and serotonin in UD-MSCs and CHO/5-HT2C cells, respectively. Our overall results argued for the possibility that LY294 and LY303 could directly affect activity of aminergic GPCRs. Thus, LY303511 and LY294002 should be used cautiously in studies of PI3K as a factor of GPCR signaling.

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Cat.No. Product Name Information
S1105 LY294002 LY294002 (SF 1101, NSC 697286) is the first synthetic molecule known to inhibit PI3Kα/δ/β with IC50 of 0.5 μM/0.57 μM/0.97 μM, respectively; more stable in solution than Wortmannin, and also blocks autophagosome formation. It not only binds to class I PI3Ks and other PI3K-related kinases, but also to novel targets seemingly unrelated to the PI3K family. LY294002 also inhibits CK2 with IC50 of 98 nM. LY294002 is a non-specific DNA-PKcs inhibitor and activates autophagy and apoptosis.

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PI3K Autophagy