A-kinase anchor protein 75 increases the rate and magnitude of cAMP signaling to the nucleus.
A-kinase anchor protein 75 (AKAP75) binds regulatory subunits (RIIalpha and RIIbeta) of type II protein kinase A (PKAII) isoforms and targets the resulting complexes to sites in the cytoskeleton that abut the plasma membrane [1-7]. Co-localization of AKAP75-PKAII with adenylate cyclase and PKA substrate/effector proteins in cytoskeleton and plasma membrane effects a physical and functional integration of up-stream and downstream signaling proteins, thereby ensuring efficient propagation of signals carried by locally generated cyclic AMP (cAMP) [4-9]. An important, but previously untested, prediction of the AKAP model is that efficient, cyclic nucleotide-dependent liberation of diffusible PKA catalytic subunits from cytoskeleton-bound AKAP75-PKAII complexes will also enhance signaling to distal organelles, such as the nucleus. We tested this idea by suing HEK-A75 cells, in which PKAII isoforms are immobilized in cortical cytoskeleton by AKAP75. Abilities of HEK-A75 and control cells (with cytoplasmically dispersed PKAII isoforms) to respond to increases in cAMP content were compared. Cells with anchored PKAII exhibited a threefold higher level of nuclear catalytic subunit content and 4-10-fold greater increments in phosphorylation of a regulatory serine residue in cAMP response element binding protein (CREB) and in phosphoCREB-stimulated transcription of the c-fos gene. Each effect occurred more rapidly in cells containing targeted AKAP75-PKAII complexes. Thus, anchoring of PKAII in actin cortical cytoskeleton increases the rate, magnitude and sensitivity of cAMP signaling to the nucleus.
Feliciello
A
A
Department of Molecular Pharmacology, Atran Laboratories, Albert Einstein College of Medicine, Bronx, New York, New York 10461, USA.
Li
Y
Y
Avvedimento
E V
EV
Gottesman
M E
ME
Rubin
C S
CS
D002352:Carrier Proteins; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D054754:Cyclic AMP-Dependent Protein Kinase RIIalpha Subunit; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013873:Thionucleotides / Q000494:pharmacology
D002352:Carrier Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D054754:Cyclic AMP-Dependent Protein Kinase RIIalpha Subunit; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit; D011506:Proteins; D016760:Proto-Oncogene Proteins c-fos; D011993:Recombinant Fusion Proteins; D013873:Thionucleotides; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D000242:Cyclic AMP; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases