mAKAP: an A-kinase anchoring protein targeted to the nuclear membrane of differentiated myocytes.
The compartmentalization of second messenger-activated protein kinases contributes to the fidelity of hormone-mediated signal transduction events. For example, the cAMP-dependent protein kinase is tethered at specific intracellular locations through association with A-kinase anchoring proteins (AKAPs). We now report the cloning of mAKAP, an anchoring protein found predominantly in heart, skeletal muscle and brain, and whose expression is induced in neonatal ventriculocytes by treatment with hypertrophic stimuli. mAKAP is targeted to the nuclear membrane of differentiated myocytes. Analysis of mAKAP-green fluorescent protein (GFP) fusion constructs revealed that nuclear membrane targeting is conferred by two regions of the protein, between residues 772-915 and 915-1065, which contain spectrin-like repeat sequences. Heterologous expression of the mAKAP targeting sequences displaced the endogenous anchoring protein from the nuclear membrane, demonstrating that mAKAP targeting is saturable. Collectively, these data suggest that a domain containing spectrin-like repeats mediates targeting of the anchoring protein mAKAP and the cAMP-dependent protein kinase holoenzyme to the nuclear membrane in response to differentiation signals.
Kapiloff
M S
MS
Howard Hughes Medical Institute, L-474, Vollum Institute, Portland OR 97201-3098, USA.
Schillace
R V
RV
Westphal
A M
AM
Scott
J D
JD
D054758:A Kinase Anchor Proteins; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000831:Animals, Newborn; D000906:Antibodies; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D017868:Cyclic AMP-Dependent Protein Kinases / Q000032:analysis*; D005455:Fluorescent Antibody Technique; D015971:Gene Expression Regulation, Enzymologic; D006352:Heart Ventricles / Q000166:cytology; D006801:Humans; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D018485:Muscle Fibers, Skeletal / Q000737:chemistry* / Q000166:cytology / Q000201:enzymology; D016296:Mutagenesis / Q000502:physiology; D009206:Myocardium / Q000737:chemistry* / Q000166:cytology / Q000201:enzymology; D009685:Nuclear Envelope / Q000737:chemistry* / Q000201:enzymology; D010446:Peptide Fragments / Q000032:analysis / Q000276:immunology; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary; D051381:Rats; D017386:Sequence Homology, Amino Acid; D013049:Spectrin / Q000032:analysis / Q000737:chemistry / Q000235:genetics
D054758:A Kinase Anchor Proteins; C093173:AKAP6 protein, human; D048868:Adaptor Proteins, Signal Transducing; C484293:Akap6 protein, rat; D000906:Antibodies; D002352:Carrier Proteins; D010446:Peptide Fragments; D013049:Spectrin; D017868:Cyclic AMP-Dependent Protein Kinases