Phosphorylation of protein phosphatase type-1 inhibitory proteins by integrin-linked kinase and cyclic nucleotide-dependent protein kinases.
Protein phosphatases play key roles in cellular regulation and are subjected to control by protein inhibitors whose activity is in turn regulated by phosphorylation. Here we investigated the possible regulation of phosphorylation-dependent type-1 protein phosphatase (PP1) inhibitors, CPI-17, PHI-1, and KEPI, by various kinases. Protein kinases A (PKA) and G (PKG) phosphorylated CPI-17 at the inhibitory site (T38), but not PHI-1 (T57). Phosphorylated CPI-17 inhibited the activity of both the PP1 catalytic subunit (PP1c) and the myosin phosphatase holoenzyme (MPH) with IC(50) values of 1-8 nM. PKA predominantly phosphorylated a site distinct from the inhibitory T73 in KEPI, whereas PKG was ineffective. Integrin-linked kinase phosphorylated KEPI (T73) and this dramatically increased inhibition of PP1c (IC(50)=0.1 nM) and MPH (IC(50)=8 nM). These results suggest that the regulatory phosphorylation of CPI-17 and KEPI may involve distinct kinases and signaling pathways.
Erdodi
Ferenc
F
Department of Medical Chemistry, Medical and Health Science Center, University of Debrecen, H-4012 Debrecen, 18/B, Bem tér, Hungary. erdodi@jaguar.dote.hu
Kiss
Eniko
E
Walsh
Michael P
MP
Stefansson
Bjarki
B
Deng
Jing Ti
JT
Eto
Masumi
M
Brautigan
David L
DL
Hartshorne
David J
DJ
D000818:Animals; D002645:Chickens; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D020128:Inhibitory Concentration 50; D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins / Q000378:metabolism; D009154:Mutation; D043263:Myosin-Light-Chain Phosphatase; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D013997:Time Factors; D014422:Turkeys; D000099200:Scaffold Protein ILK
D017868:Cyclic AMP-Dependent Protein Kinases; D018844:Cyclin-Dependent Kinases; D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins; D043263:Myosin-Light-Chain Phosphatase; D010749:Phosphoprotein Phosphatases; D010750:Phosphoproteins; D010744:Phosphoric Monoester Hydrolases; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D000099200:Scaffold Protein ILK; C107507:PPP1R14A protein, human; C454464:PPP1R14C protein, human; C073882:phosphoprotein phosphatase inhibitor 1