Inhibitory Effect of the Phosphoinositide 3-Kinase Inhibitor LY294002 on Muscarinic Acetylcholine Receptor-Induced Calcium Entry in PC12h Cells

Abstract

Abstract. Phosphoinositide-3 kinase (PI3K) and phospholipase C (PLC) utilize the same phosphoinositides as substrates to produce different signaling molecules. These enzymes are activated by a similar set of cell signaling mechanisms, i.e., tyrosine kinases and G proteins, and affect common cell functions, including proliferation, motility, and intracellular trafficking. Despite these similarities, the interplay between these enzymes is not well understood. To address this issue, the effects of the PI3K inhibitor LY294002 on carbachol-induced calcium increase in PC12h cells were examined. As carbachol stimulates both Gq-and Gi-coupled muscarinic acetylcholine receptors (mAChRs), PI3K and PLC are activated simultaneously in this protocol. LY294002 was found to reduce the carbachol-induced calcium increase, and the reduction was attributed to suppression of calcium entry. As LY294002 did not affect either carbachol-induced calcium release or calcium entry induced by calcium store depletion, this agent was found to suppress calcium entry directly activated by mAChRs. Although PI3K was supposed to compete for substrates with PLC, the PI3K inhibitor did not enhance PLC-dependent cellular responses. As LY294002 was still effective by treating cells after carbachol stimulation, it is likely that this agent blocks the calcium entry channels directly.

Differential effects of LY294002 and wortmannin on inducible nitric oxide synthase expression in glomerular mesangial cells

“…LY294002 was identified as not being exclusively selective toward the PI3K inhibitor, but as inhibiting non-lipid kinases, such as casein kinase (CK)2, mammalian target of rapamycin (mTOR), and glycogen synthase kinase 3 (GSK) [36,37]. It also has additional novel targets that are unrelated to the PI3K family or kinases; for example, it acts directly on the human Kv 1.5 channel as an open channel blocker [38] and blocks calcium entry channels in PC12 cells [39]. Moreover, by binding directly to the estrogen receptor, LY294002 inhibits the 17β-estradiol-induced transcriptional activity of an estrogen-sensitive reporter gene [40].…”

Signaling mechanisms mediating muscarinic enhancement of GABAergic synaptic transmission in the spinal cord

“…Activation of the M 2 subtype also enhances the voltage-gated Ca 2+ channel current through PI3K in myocytes (Callaghan et al, 2004). Conversely, inhibition of the PI3K with LY294002 reduces mAChR-induced Ca 2+ influx in PC12 cells (Morita et al, 2007). In this study, we found that inhibition of PI3K with two structurally dissimilar inhibitors, wortmannin and LY294002, completely blocked the effect of oxotremorine-M on the frequency of sIPSCs in 40-48% neurons.…”

Pigment epithelium–derived factor down regulates hyperglycemia-induced apoptosis via PI3K/Akt activation in goat retinal pericytes

“…These enzymes are activated by a similar set of cell signaling mechanisms, i.e., tyrosine kinases and G proteins, and affect common cell functions, including proliferation, motility, and intracellular trafficking [37]. LY294002 is a structurally distinct PI3K inhibitor that suppresses the activity of this kinase through different mechanisms.…”