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Regulation of the Nuclear PKA Holoenzyme
Author(s) -
Clister Terri,
Zhang Jin
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.lb83
Subject(s) - adenylyl cyclase , microbiology and biotechnology , lipid microdomain , protein kinase a , chemistry , kinase , protein subunit , biophysics , signal transduction , biochemistry , biology , membrane , gene
cAMP and PKA activity is regulated in time and space to ensure proper cellular responses. Recently a novel pool of activatable PKA holoenzyme was discovered to reside in the nucleus, expanding the traditional model of PKA signaling. Live‐cell imaging suggested that the regulation of the nuclear PKA holoenzyme is dependent on A‐Kinase Anchoring Proteins (AKAPs) and phosphordiesterases (PDEs). Specifically, we hypothesized that PDEs anchored to AKAPs create a local microdomain with a lower concentration of cAMP, thus controling the activation of anchored nuclear PKA. Co‐IP experiments using nuclear extracts revealed that both the RIIα subunit of the PKA holoenzyme, and PDE4D isoforms interact with AKAP95, supporting this hypothesis and providing specific candidates to further explore this regulation. Our ICUE3 cAMP biosensor was localized to AKAP95 to measure the levels of cAMP directly around AKAP95 in response to differently localized sources of cAMP. We are able to generate cAMP in different cellular compartments using targeted soluble adenylyl cyclase (sAC) and activating it in a dose‐dependent manner with sodium bicarbonate. When a low concentration of cAMP is generated, only cAMP produced in the nucleus can be detected in the vicinity AKAP95, whereas cAMP produced at the plasma membrane was not detected within this microdomain. Conversely, the AKAP95 microdomain was able to sense a large cAMP signal regardless of whether it was produced at the plasma membrane or in the nucleus. These results support the hypothesis that AKAP95 and PDE4Ds create a microdomain that prevents the activation of scaffolded nuclear PKA holoenzyme except by local cAMP signals.