INDUCTION OF CALMODULIN KINASE-IV BY THE THYROID-HORMONE DURING THE DEVELOPMENT OF RAT-BRAIN

This communication reports the specific induction of calmodulin kinase IV by the thyroid hormone 3,3',5-triiodo-L-thyronine (T-3) in a time and concentration-dependent manner at a very early stage of brain diff erentiation using a fetal rat telencephalon primary cell culture syste m, which can grow and differentiate under chemically defined condition s. The induction of the enzyme that can be observed both on the mRNA a nd on the protein level is T-3-specific, i.e. it cannot be induced by retinoic acid or reverse T-3, and can be inhibited on both the transcr iptional and the translational level by adding to the culture medium a ctinomycin D or cycloheximide, respectively. The earliest detection of calmodulin kinase IV in the fetal brain tissue of the rat is at days E16/E17, both on the mRNA as well as on the protein level. This is the first report in which a second messenger-dependent kinase involved in the control of cell regulatory processes is itself controlled by a pr imary messenger, the thyroid hormone.