Activation of C-kinase eta through its cholesterol-3-sulfate-dependent phosphorylation by casein kinase I in vitro.
The physiological correlation between casein kinase I (CK-I) and an isoform eta of protein kinase C (C-kinase eta) was investigated in vitro, since it has been reported that (i) cholesterol-3-sulfate (CH-3S) effectively activates C-kinase eta rather than the other isoforms (C-kinase epsilon and C-kinase delta) in vitro; and (ii) CK-I efficiently phosphorylates CH-3S-binding proteins, such as high mobility group protein 1 (HMG1), in the presence of CH-3S in vitro. We found that (i) CK-I phosphorylated Thr in preference to Ser on recombinant human C-kinase isoform eta (rhC-kinase eta) in the presence of CH-3S; (ii) this phosphorylation was selectively inhibited by CK-I-7 (a CK-I inhibitor); and (iii) the activity (phosphorylation of protamine sulfate) of rhC-kinase eta was approx. 3.2-fold stimulated by its full phosphorylation by CK-I in the presence of 3 microM CH-3S. These results suggest that CK-I is a protein kinase responsible for the activation of rhC-kinase eta in the presence of CH-3S in vitro.
Okano
Maiko
M
Laboratory of Genetical Biochemistry and Signal Biology, Graduate School of Medical Sciences, Kitasato University, 1-15-1 Kitasato, Sagamihara 228-8555, Japan.
Yokoyama
Takamasa
T
Miyanaga
Takahiro
T
Ohtsuki
Kenzo
K
D000818:Animals; D047388:Casein Kinases; D002788:Cholesterol Esters / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000378:metabolism; D019606:Phosphoamino Acids / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism
D002788:Cholesterol Esters; D007527:Isoenzymes; D019606:Phosphoamino Acids; D011994:Recombinant Proteins; D011494:Protein Kinases; C081975:protein kinase C eta; D047388:Casein Kinases; D011493:Protein Kinase C; C007045:cholesteryl sulfate