PATTERN OF POTASSIUM CHANNEL EXPRESSION IN PROLIFERATING B-LYMPHOCYTES DEPENDS UPON THE MODE OF ACTIVATION

Ionic channel expression is highly regulated during mitogenesis. But i t is not clear whether these regulations only follow intrinsic program s during the course of the cell cycle or if they also depend upon the external factors used to promote cell activation. B lymphocytes expres s two classes of potassium channels and can be stimulated to enter the cell cycle by distinct pathways. Thus, we have analyzed, with the pat ch-clamp technique, if the expression of channels varies when the cell s are activated by different signals that lead to cell proliferation. We found that stimulation through Ag receptors increases the expressio n of calcium- and voltage-activated potassium channels, whereas a bact erial mitogen, LPS, only enhances the expression of the latter. Moreov er, channel expression can still be modified in proliferating cells be cause stimulation of LPS-activated cells through Ag receptors induces rapid expression of calcium-activated channels. The use of inhibitors of mRNA synthesis revealed that this process depends upon gene transcr iption. Thus, differential induction of the expression of potassium ch annels is not only linked to the entry into the cell cycle but depends also on pathways of stimulation.