ABSTRACT
mAKAP (muscle-selective A-kinase-anchoring protein) co-ordinates a cAMP-sensitive negative-feedback loop comprising PKA (cAMP-dependent protein kinase) and the cAMP-selective PDE4D3 (phosphodiesterase 4D3). In vitro and cellular experiments demonstrate that PKA-phosphorylation of PDE4D3 on Ser-13 increases the affinity of PDE4D3 for mAKAP. Our data suggest that activation of mAKAP-anchored PKA enhances the recruitment of PDE4D3, allowing for quicker signal termination.
Subject(s)
3',5'-Cyclic-AMP Phosphodiesterases/metabolism , Adaptor Proteins, Signal Transducing/physiology , Cyclic AMP-Dependent Protein Kinases/metabolism , Binding Sites , Cyclic Nucleotide Phosphodiesterases, Type 4 , Enzyme Activation/physiology , Humans , Kidney/cytology , Kidney/embryology , Kidney/enzymology , Molecular Mimicry/physiology , Peptide Fragments/metabolism , Peptides/metabolism , Phosphorylation , Protein Binding/physiology , Protein Interaction Mapping , Serine/metabolismABSTRACT
The targeting of phosphatase PP2B or calcineurin toward certain substrates synchronizes a variety of physiological processes. This review emphasizes how the targeting of calcineurin through interaction with various anchoring proteins facilitates phosphatase regulation of T-cell activation, neuronal excitability and cardiac hypertrophy.
Subject(s)
Calcineurin/metabolism , Cardiomegaly/metabolism , DNA-Binding Proteins/metabolism , Muscle Proteins/metabolism , Nuclear Proteins , Receptors, AMPA/metabolism , Signal Transduction/physiology , Transcription Factors/metabolism , Animals , Binding Sites , Humans , Intracellular Signaling Peptides and Proteins , NFATC Transcription Factors , Protein BindingABSTRACT
Compartmentalization of kinases and phosphatases is a key determinant in the specificity of second messenger-mediated signaling events. Localization of the cAMP-dependent protein kinase (PKA) and other signaling enzymes is mediated by interaction with A-kinase anchoring proteins (AKAPs). This study focused on recent advances that further our understanding of AKAPs, with particular emphasis on the bidirectional regulation of signaling events by AKAP signaling complexes and their contribution to the control of actin reorganization events.
Subject(s)
Intracellular Membranes/enzymology , Phosphoric Monoester Hydrolases/metabolism , Protein Kinases/metabolism , Signal Transduction/physiology , Actins/physiology , Animals , Cyclic AMP-Dependent Protein Kinases/physiology , Cytoskeleton/physiology , Humans , Membrane Proteins/physiologyABSTRACT
Compartmentalization of protein kinases and phosphatases with substrates is a means to increase the efficacy of signal transduction events. The A-kinase anchoring protein, AKAP79, is a multivalent anchoring protein that maintains the cAMP-dependent protein kinase, protein kinase C, and protein phosphatase-2B (PP2B/calcineurin) at the postsynaptic membrane of excitatory synapses where it is recruited into complexes with N-methyl-d-aspartic acid or alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA)-subtype glutamate receptors. We have used cellular targeting of AKAP79 truncation and deletion mutants as an assay to map the PP2B-binding site on AKAP79. We demonstrate that residues 315-360 are necessary and sufficient for AKAP79-PP2B anchoring in cells. Multiple determinants contained within this region bind directly to the A subunit of PP2B and inhibit phosphatase activity. Peptides spanning the 315-360 region of AKAP79 can antagonize PP2B anchoring in vitro and targeting in transfected cells. Electrophysiological experiments further emphasize this point by demonstrating that a peptide encompassing residues 330-357 of AKAP79 attenuates PP2B-dependent down-regulation of GluR1 receptor currents when perfused into HEK293 cells. We propose that the structural features of this AKAP79-PP2B-binding domain may share similarities with other proteins that serve to coordinate PP2B localization and activity.