RECEPTOR-MEDIATED STIMULATION OF LIPID SIGNALING PATHWAYS IN CHO CELLS ELICITS THE RAPID TRANSIENT INDUCTION OF THE PDE1B ISOFORM OF CA2+ CALMODULIN-STIMULATED CAMP-PHOSPHODIESTERASE/

Chinese hamster ovary cells (CHO cells) do not exhibit any Ca2+/calmod ulin-stimulated cAMP phosphodiesterase (PDE1) activity. Challenge of C HO cells with agonists for endogenous P-2-purinoceptors, lysophosphati dic acid receptors and thrombin receptors caused a similar rapid trans ient induction of PDE1 activity in each instance. This was also eviden t on noradrenaline challenge of a cloned CHO cell line transfected so as to overexpress alpha(1B)-adrenoceptors. This novel PDE1 activity ap peared within about 15 min of exposure to ligands, rose to a maximum v alue within 30 min to 1 h and then rapidly decreased. In each case, th e expression of novel PDE1 activity was blocked by the transcriptional inhibitor actinomycin D. Challenge with insulin of either native CHO cells or a CHO cell line transfected so as to overexpress the human in sulin receptor failed to induce PDE1 activity. Reverse transcriptase-P CR analyses, using degenerate primers able to detect the PDE1C isoform , did not amplify any fragment from RNA preparations of CHO cells expr essing PDE1 activity, although they did so from the human thyroid carc inoma FTC133 cell line. Reverse transcriptase-PCR analyses, using dege nerate primers able to detect the PDE1A and PDE1B isoforms, successful ly amplified a fragment of the predicted size from RNA preparations of both CHO cells expressing PDE1 activity and human Jurkat T-cells. Seq uencing of the PCR products, generated using the PDE1A/B primers, yiel ded a novel sequence which, by analogy with sequences reported for bov ine and murine PDE1B forms, suggests that the PDE1 species induced in CHO cells through protein kinase C activation and that expressed in Ju rkat T-cells are PDE1B forms.