Multiple splice variants of phosphodiesterase PDE4C cloned from human lung and testis.
Four closely related cyclic-nucleotide specific phosphodiesterase (PDE4) genes have been identified in both humans and rats: PDE4A, 4B, 4C and 4D. We have now cloned cDNAs for multiple splice variants of human PDE4C. Two splice variants, PDE4C-791 and PDE4C-426, were isolated from a fetal lung library. The longest open reading frame (ORF) of 791 amino acids (aa) is encoded by PDE4C-791, which is similar to a recently described cDNA [Engels, P., Sullivan, M., Muller, T. and Lubbert, H. FEBS Lett. 358 (1995) 305-10], except that an alternative 5'-end sequence upstream of the first methionine extends the PDE4C-791 ORF by 79 aa. The PDE4C-426 variant contains 3 insertions that are located 5' to the catalytic domain and encode several in-frame stop codons. The predicted 426 aa protein initiates at a methionine 365 aa within PDE4C-791. A baculovirus clone starting at this methionine expressed an enzymatically active protein. Two additional splice variants, PDE4C-delta54 and PDE4C-delta109, were found in testis mRNA. PDE4C-delta54 contained a novel 5'-end region and a deletion of 162 nt; the predicted protein deletes 54 aa from the amino-terminal region. The PDE4C-delta54 protein produced in baculovirus-infected cells was enzymatically active and sensitive to PDE4-specific inhibitors. The PDE4C-delta109 protein is similar to PDE4C-delta54 but has an additional 55 aa deleted in the catalytic domain; it lacked enzymatic activity. Analysis of uncloned total mRNA from 4 tissue sources by polymerase chain reaction (PCR) confirmed the presence of mRNAs with the two deletions and three insertions that we observed in cDNA clones. The PDE4C-delta54 variant was found only in testis and the 5'-extended region of PDE4C-791 was seen only in lung and the melanoma cell line G361. Hence, tissue-specific expression of various PDE4C isoforms should be considered in understanding how these gene products modulate cellular responses to cAMP.
Obernolte
R
R
Roche Bioscience, Palo Alto, CA 94304, USA.
Ratzliff
J
J
Baecker
P A
PA
Daniels
D V
DV
Zuppan
P
P
Jarnagin
K
K
Shelton
E R
ER
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000737:chemistry / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D018076:DNA, Complementary / Q000235:genetics; D005333:Fetus; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D008168:Lung / Q000201:enzymology*; D008297:Male; D008545:Melanoma; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009928:Organ Specificity; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D012326:RNA Splicing / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D011994:Recombinant Proteins; D020889:Rolipram; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion / Q000235:genetics; D013737:Testis / Q000201:enzymology*; D014407:Tumor Cells, Cultured
D018076:DNA, Complementary; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; D012333:RNA, Messenger; D011994:Recombinant Proteins; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; C517355:PDE4A protein, human; C517361:PDE4C protein, human; D020889:Rolipram