Multiple splice variants of phosphodiesterase PDE4C cloned from human lung and testis

• Published in: Biochimica et biophysica acta Vol. 1353; no. 3; pp. 287 - 297
• Main Authors: Obernolte, Rena, Ratzliff, James, Baecker, Preston A, Daniels, Donald V, Zuppan, Patti, Jarnagin, Kurt, Shelton, Earl R
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 12.09.1997
• Subjects: 3',5'-Cyclic-AMP Phosphodiesterases - chemistry; 3',5'-Cyclic-AMP Phosphodiesterases - genetics; Alternative mRNA 5′ end; Amino Acid Sequence; Base Sequence; cAMP-specific; cDNA; Cloning, Molecular; Cyclic Nucleotide Phosphodiesterases, Type 4; DNA, Complementary - genetics; Fetus; Gene Expression Regulation, Enzymologic - drug effects; Humans; Lung - enzymology; Male; Melanoma; Molecular Sequence Data; Molecular Weight; Nucleotide sequence; Organ Specificity; PCR; Phosphodiesterase Inhibitors - pharmacology; Pyrrolidinones - pharmacology; Recombinant Proteins; RNA Splicing - genetics; RNA, Messenger - analysis; RNA, Messenger - genetics; Rolipram; Sequence Analysis, DNA; Sequence Deletion - genetics; Testis - enzymology; Tumor Cells, Cultured; Alternative mRNA 5′ end; cDNA; Rolipram; Nucleotide sequence; cAMP-specific; PCR
• ISSN: 0167-4781; 0006-3002; 1879-2634
• DOI: 10.1016/S0167-4781(97)00080-8

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 Lübbert, 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- Δ54 and PDE4C- Δ109, were found in testis mRNA. PDE4C- Δ54 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- Δ54 protein produced in baculovirus-infected cells was enzymatically active and sensitive to PDE4-specific inhibitors. The PDE4C- Δ109 protein is similar to PDE4C- Δ54 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- Δ54 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.