IPP‐1 controls Akt/CREB phosphorylation extension in A2a adenosine receptor signaling cascade in MIN6 pancreatic &bgr;‐cell line

Abstract

ABSTRACT Signaling through A2a adenosine receptor specifically prevent pancreatic &bgr;‐cells (PBCs) loses under diabetogenic conditions. However, signaling mediators of this receptor in PBCs remained unidentified. Thus, we aimed to investigate the possible involvement of PKA/Akt/IPP‐1/CREB pathway in MIN6 &bgr;‐cells. In addition, we investigated IPP‐1 role in A2a receptor signaling pathway. The expression of A2a receptor in MIN6 cell line was evaluated by RT‐PCR and its functionality confirmed by quantification of cAMP in response to the CGS 21680, an A2a receptor agonist. MTT and Brdu assays were used to evaluate cell viability and proliferation, respectively. PKA activity and insulin release were evaluated using ELISA methods. P‐Akt/Akt, p‐IPP‐1/IPP‐1, and p‐CREB/CREB levels were assessed using western blotting. IPP‐1 knock down assessments was performed using specific siRNA. Our result revealed that MIN6 cells express A2a receptor which actively increased cAMP levels (with EC50 =2.41&mgr;M) and PKA activity. Activation of this receptor increased cell viability, proliferation and insulin release. Moreover, we mentioned A2a receptor stimulation increased p‐Akt, p‐IPP‐1, and p‐CREB levels in dose (max at 10&mgr;M of CGS 21680) and time (max at 30min after CGS 21680 treatment) dependent manner. Interestingly, herein, we found in IPP‐1 knocked down cells, A2a receptor failed to activate Akt and CREB. Altogether, we mentioned that in MIN6 cells A2a receptor increase cell viability, proliferation and insulin release through PKA/Akt/IPP‐1/CREB signaling pathway. In addition, we conclude A2a receptor signaling through this pathway is dependent to activation of IPP‐1.