Association of CPI-17 with protein kinase C and casein kinase I.
The protein kinase C-potentiated inhibitor protein of 17kDa, called CPI-17, specifically inhibits myosin light chain phosphatase (MLCP). Phosphorylation of Thr-38 in vivo highly potentiates the ability of CPI-17 to inhibit MLCP. Thr-38 has been shown to be phosphorylated in vitro by a number of protein kinases including protein kinase C (PKC), Rho-associated coiled-coil kinase (ROCK), and protein kinase N (PKN). In this study we have focused on the association of protein kinases with CPI-17. Using affinity chromatography and Western blot analysis, we found interaction with all PKC isotypes and casein kinase I isoforms, CKIalpha and CKI. By contrast, ROCK and PKN did not associate with CPI-17, suggesting that PKC may be the relevant kinase that phosphorylates Thr-38 in vivo. CPI-17 interacted with the cysteine-rich domain of PKC and was phosphorylated by all PKC isotypes. We previously found that CPI-17 co-purified with casein kinase I in brain suggesting they are part of a complex and we now show that CPI-17 associates with the kinase domain of CKI isoforms.
University of Edinburgh, Division of Biomedical and Clinical Laboratory Sciences, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK.
Eva
E
Zemlickova
Franz-Josef
FJ
Johannes
Alastair
A
Aitken
Thierry
T
Dubois
D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000201:enzymology; D047388:Casein Kinases; D020134:Catalytic Domain; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000737:chemistry / Q000378:metabolism*; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary
D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; D009124:Muscle Proteins; C107507:PPP1R14A protein, human; D010750:Phosphoproteins; D011494:Protein Kinases; C089212:protein kinase D; D047388:Casein Kinases; D011493:Protein Kinase C; D010749:Phosphoprotein Phosphatases