Adenosine A2A Receptor Facilitates Calcium-Dependent Protein Secretion through the Activation of Protein Kinase A and Phosphatidylinositol-3 Kinase in PC12 Cells

Abstract

ABSTRACT. Adenosine modulates a variety of cellular functions including calcium-dependent exocytosis. Activation of adenosine A2A receptor (A2A-R) facilitates neurotransmitter release in some cell types, although the underlying mechanisms are not fully understood. In this study, we found that treatment of PC12 cells with the A2A-R agonist CGS21680 promotes calcium-evoked secretion of the fusion protein between neuropeptide Y and modified yellow fluorescence protein (NPY-Venus). CGS21680 treatment of PC12 cells transiently increased the phosphorylation of p38 and JNK MAP kinases and Akt, as well as that of ATF2 and CREB, reaching maximal levels at around 10-15 min of CGS21680 treatment. Importantly, pretreatment of PC12 cells with the PI3K inhibitor LY294002, together with the protein kinase A (PKA) inhibitor KT5720, significantly inhibited CGS21680 enhancement of calcium-dependent NPY-Venus release. Moreover, expression of a dominant-negative form of Akt and the PKA inhibitory polypeptide protein kinase inhibitor (PKI) co-operatively inhibited the facilitating effect of CGS21680 on secretion of NPY-Venus. These data suggest that the PI3K-Akt and PKA pathways play a critical role in A2A-R-mediated facilitation of calcium-dependent secretion. We also found that CGS21680 treatment promoted recruitment of the NPY-Venus-containing vesicles to the proximity of the plasma membrane at around 10-15 min of CGS21680 treatment, which may in part account for the facilitated secretion by A2A-R activation.

Negative regulation of diacylglycerol kinase θ mediates adenosine-dependent hepatocyte preconditioning

“…Biochemical evidence both in neuroblastoma 17 and in C. elegans motoneurons 14 shows that the enzymatic activity of DGKy and of its orthologue DGK-1 is strongly inhibited on direct interaction with the small GTPase RhoA. 18 Thus, we set to investigate the interaction between active RhoA and DGKy in PC12 cells,, a rat cell line expressing A2aR 19,20 transiently co-transfected with FLAGtagged DGKy and myc-tagged RhoA. Consistently with earlier published data, 18 FLAG-DGKy co-immunoprecipited with constituitvely active myc-RhoA-V14, but not with inactive myc-RhoA-N14 mutants from unstimulated cells (Figure 4).…”

Caffeine Modulates Tau Phosphorylation and Affects Akt Signaling in Postmitotic Neurons

“…Caffeine acts as an antagonist of adenosine A 1 and A 2A receptors, and it has been shown that the specific A 2A subtype receptors can positively regulate cell cycle when overstimulated (Merighi et al 2002). In this regard, activation of A 2A receptors has been reported to activate the PI3K/Akt survival/proliferation pathway (Mori et al 2004), which has been associated with pathological Aβ (Bhaskar et al 2009) and found upregulated in AD brain (Griffin et al 2005). Importantly, the spatial and temporal patterns of Akt overexpression in the AD brain coincide with those of early pathological tau changes, consistent with the notion that Akt could be involved in tau metabolism in vivo and play a protective role in cellular responses in AD-related neurodegeneration (Stein and Johnson 2002).…”

Activation of Adenosine A2A Receptor Up-Regulates BDNF Expression in Rat Primary Cortical Neurons

“…Adenosine A2 A receptor is coupled with Gs [29][30][31][32], resulted in the increased cAMP [33,34] followed by ERK1/2-CREB phosphorylation [20,35,36]. In addition, at least one report suggested that A2 A activation is coupled to the activation of PI3K-Akt pathways [37]. To investigate the role of different signaling pathways on CGS21680-induced BDNF expression, we examined the phosphorylation status of signaling pathways including Akt, ERK1/2 and CREB.…”