THE EXPRESSION OF CAMP-DEPENDENT PROTEIN-KINASE SUBUNITS IS DIFFERENTIALLY REGULATED DURING LIVER-REGENERATION

  • 15 March 1989
    • journal article
    • research article
    • Vol. 264  (8) , 4374-4382
Abstract
The levels of the regulatory (RI and RII) and catalytic (C) components of the cAMP-dependent protein kinase and of their messages were studied during the 36 h of liver regeneration after 70% heaptectomy. Both RI.alpha. mRNA and RII .alpha. mRNA started to increase 4 h after the resection, reaching peak levels after 9 h. RI mRNA decreased abruptly 9-12 h after resection, whereas RII and mRNA stayed elevated. C.alpha. mRNA was rather constant during the period of the study. In accordance with the mRNA data the level of C was constant while RI and RII increased rapidly when its message became elevated. RII, however, increased noticeably only 6-8 h after its mRNA had become elevated. The increased expression of R led to a disproportion between and R and C that was most pronounced 14 ha after resection, i.e. coinciding with the prereplicative cAMP burst. The increased R/C ratio at the time of regeneration diminished the concentration of the active C subunit during the cAMP burst. In that way the otherwise inhibitory effect of high concentrations of active C on the DNA replication may have been decreased. The fractional saturation of RI and RII by endogeous cAMP levels, although there was a tendency that RI was more highly saturated than RII at high concentrations of cAMP.

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