Abstract
Inhibitor-1 (I-1) is phosphorylated on threonine residue 35 (Thr35) by the cAMP-dependent protein kinase (PKA), inducing the potent inhibition of the serine-threonine-specific protein phosphatase 1 (PP1). We now report that the formation of a signaling complex containing PKA and I-1 by the A-kinase anchoring protein 18 (AKAP18) facilitates this regulation in cells. AKAP18 directly bound I-1, and AKAP18/I-1 complexes were isolated from both rat heart extract and transfected heterologous cells. It is noteworthy that prevention of PKA binding to the AKAP18 scaffold decreased I-1 phosphorylation by 48% in cells. Moreover, the I-1 target PP1 was also associated with AKAP18 complexes. The cAMP-mediated inhibition of phosphatase activity was contingent on PKA binding to the scaffold. These observations reveal an additional level of complexity in PP1 regulation because of its association with AKAP18 multimolecular signaling complexes and suggest that targeting of AKAP18 complexes may be an alternative method to alter phosphatase activity and modulate specific substrate dephosphorylation.
Footnotes
↵ The online version of this article (available at http://molpharm.aspetjournals.org) contains supplemental material.
This work was supported by the National Institutes of Health National Heart, Lung, and Blood Institute [Grants R01-HL82705, R01-HL075398].
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.110.065425.
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ABBREVIATIONS:
- I-1
- protein phosphatase 1 inhibitor-1
- PP1
- protein phosphatase 1
- PKA
- cAMP-dependent protein kinase
- AKAP
- A-kinase anchoring protein
- TCA
- trichloroacetic acid
- PP2A
- protein phosphatase 2A
- GFP
- green fluorescent protein
- HEK
- human embryonic kidney
- MOPS
- 3-(N-morpholino)propanesulfonic acid
- GST
- glutathione transferase
- PKI
- protein kinase I
- STREP
- Trp-Ser-His-Pro-Gln-Phe-Glu-Lys
- GADD34
- growth arrest and DNA damage protein 34
- Rp-cAMPs
- adenosine-3′,5′-cyclic monophosphorothioate, Rp-isomer.
- Received April 7, 2010.
- Accepted December 13, 2010.
- Copyright © 2011 The American Society for Pharmacology and Experimental Therapeutics
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