Bovine neurofilament-enriched preparations contain kinase activity similar to casein kinase I--neurofilament phosphorylation by casein kinase I (CKI).
Neurofilament (NF)-enriched preparations from bovine spinal cord contain regulator-independent kinase activities that phosphorylate NF subunits as well as alpha-casein. CKI-7 (N-2-amino ethyl, 5-chloroisoquinoline, 8-sulfonamide), a specific inhibitor of casein kinase I (CKI), inhibits the phosphorylation of NF subunits in the neurofilament preparation. This inhibition occurs at a concentration range identical to concentrations where CKI-7 inhibits rabbit reticulocyte CKI phosphorylation of alpha-casein. Heparin, a specific inhibitor of casein kinase II (CKII), produced only 20% inhibition of 32P incorporation into NF subunits, and only at concentrations 5 to 10-fold higher than those required to inhibit CKII from reticulocytes. CKI from rabbit reticulocytes phosphorylated all three NF subunits (NF-H, NF-M and NF-L). Comparison of the tryptic phosphopeptide maps of NF-M, phosphorylated by the NF-associated kinase and CKI, indicates that the casein kinase I phosphorylates many of the peptides phosphorylated by the NF-associated kinase and this phosphorylation occurs at the carboxy terminal tail domain of the NF-M subunit. These studies suggest that the major independent kinase activity associated with NFs is CKI.
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Laboratory of Neurochemistry, NINDS, National Institutes of Health, Bethesda, MD 20892.
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D000595:Amino Acid Sequence; D000818:Animals; D001345:Autoradiography; D047388:Casein Kinases; D002417:Cattle; D004591:Electrophoresis, Polyacrylamide Gel; D006493:Heparin / Q000494:pharmacology; D006868:Hydrolysis; D066298:In Vitro Techniques; D007382:Intermediate Filaments / Q000201:enzymology*; D007546:Isoquinolines / Q000494:pharmacology; D008969:Molecular Sequence Data; D016900:Neurofilament Proteins / Q000378:metabolism*; D010449:Peptide Mapping; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism*; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D011817:Rabbits; D012156:Reticulocytes / Q000187:drug effects / Q000201:enzymology; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism; D014357:Trypsin
D007546:Isoquinolines; D016900:Neurofilament Proteins; D047428:Protein Kinase Inhibitors; C058815:N-(2-aminoethyl)-5-chloroisoquinoline-8-sulfonamide; D006493:Heparin; D010770:Phosphotransferases; D011494:Protein Kinases; D047388:Casein Kinases; D014357:Trypsin