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Relationship Between Casein Kinase I Isoforms and a Neurofilament‐Associated Kinase
Author(s) -
Fu Zheng,
Green Calvert L,
Bennett Gudrun S.
Publication year - 1999
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1999.0730830.x
Subject(s) - gene isoform , immunoprecipitation , casein kinase 2, alpha 1 , neurofilament , kinase , casein kinase 2 , phosphorylation , biochemistry , isozyme , biology , casein kinase 1 , microbiology and biotechnology , casein , gene , map2k7 , enzyme , mitogen activated protein kinase kinase , protein kinase a , cyclin dependent kinase 2 , immunohistochemistry , immunology
: Purified neurofilaments (NFs) contain an associated kinase (NFAK) activity that phosphorylates selectively a subset of sites in the tail of NF‐M and has properties consistent with casein kinase I (CKI). Because CKI consists of a family of as many as seven genes (α, β, γ1‐3, δ, and ε), we investigated the extent to which different CKI isoforms contribute to NFAK activity. Using an NF‐M‐derived substrate, we determined that NFAK activity copurified with casein kinase activity through two purification steps. In an in‐gel kinase assay, NFAK activity occurred at 36‐40 kDa, corresponding to the size of CKIα isoforms. Chicken neurons express transcripts encoding four alternatively spliced variants of CKIα (CKIα, CKIαS, CKIαL, and CKIαLS) differing in the presence or absence of two inserts, L and S. Using antibodies against different isoforms or with broad CKI specificity, we determined that all four CKIα variants, as well as other CKI family members, are present in chicken brain. However, only CKIα and CKIαS could be detected in purified NFAK. Also, immunoprecipitation studies showed that CKIα and CKIαS together account for NFAK activity. These findings raise the possibility that only a subset of CKI isoforms may be able to associate with and/or phosphorylate NFs.