Molecular Cloning and Expression of a Human Phosphodiesterase 4C

• Published in: Cellular signalling Vol. 9; no. 8; pp. 575 - 585
• Main Authors: Owens, Raymond J, Lumb, Simon, Rees-Milton, Karen, Russell, Annette, Baldock, Darren, Lang, Volker, Crabbe, Tom, Ballesteros, Mercedes, Perry, Martin J
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 01.12.1997
• Subjects: 3',5'-Cyclic-AMP Phosphodiesterases - genetics; 3',5'-Cyclic-AMP Phosphodiesterases - metabolism; Amino Acid Sequence; Animals; Base Sequence; Catalysis; Cloning, Molecular; COS Cells; Cyclic AMP phosphodiesterase; Cyclic Nucleotide Phosphodiesterases, Type 4; DNA, Complementary; Gene Expression; Humans; Molecular Sequence Data; Rolipram; Saccharomyces cerevisiae - metabolism; Sequence Analysis, DNA; Sequence Homology, Amino Acid; Type 4C; Cyclic AMP phosphodiesterase; Rolipram; Type 4C
• ISSN: 0898-6568; 1873-3913
• DOI: 10.1016/S0898-6568(97)00072-7

A cDNA coding for a human phosphodiesterase 4C (PDE4C2) was isolated from the mRNA prepared from the glioblastoma cell line, U87. The cDNA contained an ORF of 1818 bp corresponding to a 605 amino acid polypeptide. The sequence differed at the 5′ end from the human PDE4C previously reported (Engels, P. et al, 1995 FEBs Letters 358, 305-310) indicating that it represents a novel splice variant of the human PDE4C gene. Evidence was also obtained for a third 5′ splice variant. The PDE4C2 cDNA was transfected into both COS 1 cells and yeast cells, and shown to direct the expression of an 80 kD polypeptide by Western blotting using a PDE4C specific antiserum. The activity of cell lysates was typical of PDE4 being specific for cAMP and inhibitable by the selective inhibitor, rolipram. However, the K m for cAMP of the enzyme produced in COS cells was 0.6 μM compared to 2.6 μM for the yeast 4C activity. In addition the COS cell PDE4 activity was much more sensitive to R rolipram than the yeast PDE4 enzyme (IC 50 of 23 nM compared to 1648 nM). This difference in rolipram sensitivity was associated with the detection of a high affinity [ 3H] R rolipram binding site on the COS cell 4C enzyme but not on the yeast expressed enzyme. The results indicate that the enzyme can adopt more than one active conformation, which are distinguished by their interaction with rolipram.