O-GLCNACYLATION MODULATES PKA-CREB SIGNALING IN A MANNER SPECIFIC TO PKA CATALYTIC SUBUNIT ISOFORMS

Abstract

Down-regulation of Protein kinase A (PKA)- cAMP response element binding protein (CREB) signaling is believed to be responsible for the learning and memory deficit in Alzheimer's disease (AD). It is known that isoforms a and b of PKA catalytic subunit (PKAc) and CREB are post-translationally modified with O-GlcNAc. OGT or OGA were overexpressed in HEK-293FT cells to examine the role of O-GlcNAcylation in CREB signaling. PKAc isoforms were co-transfected with OGT or OGA in N2a cells, and the effects of PKAc isoforms on O-GlcNAcylation and CREB signaling were identified. OGT was overexpressed or knocked down together with insulin treatment in HEK-293FT cells. O-GlcNAcylation and CREB signaling were checked by western blot. We found that up-regulation of O-GlcNAcylation enhanced CREB phosphorylation, but suppressed CREB expression in exogenous PKAc isoform-unspecific manner. PKAc isoforms affected exogenous expression of OGT or OGA and protein O-GlcNAcylation differently. Up-regulation of O-GlcNAcylation did not significantly affect net PKAca-CREB signaling, but enhanced PKAcb-CREB signaling. The role of O-GlcNAcylation in PKA-CREB signaling was desensitized by insulin treatment. We determined the role of O-GlcNAcylation in PKAc isoform-specific CREB signaling. Our data suggests O-GlcNAcylation modulates PKA-CREB signaling by regulating expression and phosphorylation of CREB in a PKAc isoform-specific manner.