Role of protein kinase A and class II phosphatidylinositol 3-kinase C2 beta in the downregulation of KCa3.1 channel synthesis and membrane surface expression by lyso-globotriaosylceramide

Abstract

The intermediate conductance calcium-activated potassium channel (KCa3.1) mediates proliferation of many cell types including fibroblasts, and is a molecular target for intervention in various cell proliferative diseases. Our previous study showed that reduction of KCa3.1 channel expression by lyso-globotriaosylceramide (lyso-Gb3) inhibits differentiation into myofibroblasts and collagen synthesis, which might lead to development of ascending thoracic aortic aneurysm secondary to Fabry disease. However, how lyso-Gb3 downregulates KCa3.1 channel expression is unknown. Therefore, we aimed to investigate the underlying mechanisms of lyso-Gb3-mediated KCa3.1 channel downregulation, focusing on the cAMP signaling pathway. We found that lyso-Gb3 increased the intracellular cAMP concentration by upregulation of adenylyl cyclase 6 and inhibited ERIC 1/2 phosphorylation through the protein kinase A (PICA) pathway, leading to the inhibition of KCa3.1 channel synthesis, not the exchange protein directly activated by cAMP (Epac) pathway. Moreover, lyso-Gb3 suppressed expression of class II phosphatidylinositol 3-kinase C2 beta (PI3KC2 beta) by PICA activation, which reduces the production of phosphatidylinositol 3-phosphate [PI(3)P], and the reduced membrane surface expression of KCa3.1 channel was recovered by increasing the intracellular levels of PI(3)P. Consequently, our findings that lyso-Gb3 inhibited both KCa3.1 channel synthesis and surface expression by increasing intracellular cAMP, and controlled surface expression through changes in PI3KC2 beta-mediated PI(3)P production, suggest that modulation of PICA and PI3KC2 beta activity to control of KCa3.1 channel expression can be an alternative important target to attenuate ascending thoracic aortic aneurysms in Fabry disease. (C) 2016 Elsevier Inc. All rights reserved.