Role of Autophosphorylation in Regulation of Protein Kinase CK2 from Rat Neuronal Chromatin

O. G. Kulikova^* and B. A. Reikhardt

Institute for Experimental Medicine, Russian Academy of Medical Sciences, ul. Akademika Pavlova 12, St. Petersburg, 197376 Russia; fax: (812) 234-9489; E-mail: root@pharm.iem.ras.spb.ru

^* To whom correspondence should be addressed.

Received January 13, 1998; Revision received March 16, 1998

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The regulation of rat brain cortex protein kinase CK2 (casein kinase 2) by autophosphorylation has been investigated. Purified CK2 from rat neuronal chromatin is composed of two regulatory (beta) and two catalytic (alpha and/or alpha´) subunits. The molecular masses of the subunits--43 (alpha), 39 (alpha´), and 25 kD (beta)--were similar to those of typical CK2 subunits. A significant amount of alpha´-subunit occurred in neuronal chromatin; the molar ratios for the subunits were 1.1:0.9:1.9. Pharmacological probes (derivatives of 4,5-di(N-methylcarbamoyl)-1-alkyl-imidazole) were used to study autophosphorylation of separate subunits. These compounds have different effects on neuronal chromatin CK2, transcription, and neurological memory. Changes in the autophosphorylation of the CK2 subunits were found with the help of these compounds. Inhibitors of transcription decreased the beta-subunit autophosphorylation. Stimulators of transcription increased the beta-subunit autophosphorylation and promoted the autophosphorylation of the alpha´ (but not the alpha) subunit. The beta-subunit autophosphorylation led to reduction in phosphorylation of nonhistone HMG 14 protein that has been shown to be a physiological substrate of CK2. The autophosphorylation of the alpha´-subunit raised the CK2 activity with HMG 14. The question of functional distinctions between the alpha´- and alpha-subunits of chromatin CK2 in differentiated neurons is discussed.

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KEY WORDS: protein kinase CK2, casein kinase 2, subunit, autophosphorylation, protein phosphorylation, HMG proteins, chromatin, neurons, brain

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