CALMODULIN EXPRESSION DURING PROLIFERATIVE ACTIVATION OF HUMAN T-LYMPHOCYTES

We have investigated the levels of calmodulin mRNA species and calmodu lin protein during proliferation of human T lymphocytes. Quiescent lym phocytes expressed the 1.7 kb transcript of CaM I, the 1.4 kb of CaM I I and the 2.3 kb of CaM III. Phytohaemagglutinin added to peripheral b lood lymphocytes induced DNA replication which started at 48 h and rea ched a maximum at 72 h after activation. All the species of calmodulin mRNAs, including the 4.0 kb transcript of CaM I and the 0.8 kb of CaM III which were not detected in quiescent cells, increased during lymp hocyte proliferation. At 72 h after activation, the increase of CaM I and CaM II transcripts were found to be 2-fold whereas CaM III mRNAs i ncreased 9-fold. The cellular content of calmodulin protein was also f ound to increase during proliferation and calmodulin accumulations in cytosol and nuclei of activated cells were observed. Two calmodulin bi nding proteins of 180 and 170 kD were found to increase in the nuclei of proliferating lymphocytes, whereas on the contrary 3 other calmodul in binding proteins of 110, 62 and 60 kD decreased during proliferatio n.