An Isoform of the Neuronal Cyclin-dependent Kinase 5 (Cdk5) Activator (*)
- Damu Tang(1),
- Jeffery Yeung(2),
- Ki-Young Lee(2),
- Masayuki Matsushita(3),
- Hideki Matsui(4),
- Kazuhito Tomizawa(3),
- Osamu Hatase(3) and
- Jerry H. Wang(1)(2)(§)
- From the (1) Department of Biochemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, the
- (2) Medical Research Council Group in Signal Transduction, Department of Medical Biochemistry, University of Calgary, Calgary, Alberta T2N 4N1, Canada, the
- (3) Department of Physiology, Kagawa Medical School, 1750-1 Ikenbe, Miki, Kagawa 761-07, Japan, and the
- (4) Department of Physiology, Okayama University Medical School, 2-5-1 Shikata, Okayama 700, Japan
- § To whom correspondence should be addressed: Dept. of Biochemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong. Tel.: 852-1358-8701; Fax: 852-2358-1552.
Abstract
Neuronal Cdc2-like kinase is a heterodimer of Cdk5 and a 25-kDa subunit that is derived from a 35-kDa brain- and neuron-specific
protein called the neuronal Cdk5 activator (p35/p25
) (Lew, J., Huang, Q.-Q., Qi, Z., Winkfein, R. J., Aebersold, R., Hunt, T., and Wang, J. H.(1994) Nature 371, 423-426; Tsai, L. H., Delalle, I., Caviness, V. S., Jr., Chae, T., and Harlow, E.(1994) Nature 371, 419-423). Upon screening of a human hippocampus library with a bovine Nck5a cDNA, we uncovered a distinct clone encoding
a 39-kDa isoform of Nck5a. The isoform, designated the neuronal Cdk5 activator isoform (p39
), showed a high degree of sequence similarity to p35
with 57% amino acid identity. Northern blot analysis detected its mRNA transcript in bovine and rat cerebrum and cerebellum,
but not in any other rat tissues examined. In situ hybridization showed that Nck5ai was enriched in CA1 to CA3 of the hippocampus, but absent in the fimbria of hippocampal
formation. Among seven cell lines in proliferating cultures, only PC12 and N2A, two cell lines capable of differentiating
into neuron-like cells, were found to contain Nck5ai mRNA. A 30-kDa truncated form of Nck5ai expressed as a glutathione S-transferase fusion protein in Escherichia coli] was found to associate with Cdk5 to form an active Cdk5 kinase. Thus, the isoform shares many common characteristics with
p35
, including Ckd5 activating activity and brain- and neuron-specific expression. Both proteins show limited sequence homology
to cyclins, suggesting that they define a new family of cyclin-dependent kinase-activating proteins.
Footnotes
-
↵* This work was supported in part by operating grants from the Medical Research Council of Canada and the National Cancer Institute of Canada. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) U34051[GenBank].
-
↵1 The abbreviations used are:
- Cdks
-
cyclin-dependent kinases
- kb
-
kilobase(s)
- Pipes
-
1,4-piperazinediethanesulfonic acid
- Mops
-
4-morpholinepropanesulfonic acid
- GST
-
glutathione S-transferase
- DTT
-
dithiothreitol.
-
↵2 K. Tomizawa, H. Matsui, M. Matsushita, J. Lew, M. Tokuda, T. Itano, R. Konishi, J. H. Wang, and O. Hatase, submitted for publication.
-
- Received February 27, 1995.
- Revision received August 8, 1995.
- © 1995 by The American Society for Biochemistry and Molecular Biology, Inc.
