Identification and characterization of PDE4A11, a novel, widely expressed long isoform encoded by the human PDE4A cAMP phosphodiesterase gene.

ABSTRACT

PDE4A11 is a novel cAMP-specific phosphodiesterase that is conserved in humans, mouse, rat, pig, and bat. Exon-1(4A11) encodes its unique, 81 amino acid N-terminal region. Reverse-transcriptase polymerase chain reaction performed across the splice junction, plus identification of expressed sequence tags, identifies PDE4A11 as a long isoform possessing UCR1 and UCR2 regulatory domains. Transcript analysis shows that PDE4A11 is widely expressed compared with PDE4A10 and PDE4A4B long isoforms. Truncation analysis identifies a putative promoter in a 250-base pair region located immediately upstream of the start site in Exon-1(4A11). Recombinant PDE4A11, expressed in COS-7 cells, is a 126-kDa protein localized predominantly around the nucleus and in membrane ruffles. PDE4A11 exhibits a K(m) for cAMP hydrolysis of 4 microM, with relative V(max) similar to that of PDE4A10 and PDE4A4B. PDE4A11 is dose-dependently inhibited by rolipram, 4-[(3-butoxy-4-methoxyphenyl)-methyl]-2-imidazolidinone (Ro 20-1724), cilomilast, roflumilast, and denbufylline, with IC(50) values of 0.7, 0.9, 0.03, 0.004, and 0.3 microM, respectively. Soluble and particulate PDE4A11 exhibit distinct rates of thermal inactivation (55 degrees C; T((0.5)) = 2.5 and 4.4 min, respectively). Elevating cAMP levels in COS-7 cells activates PDE4A11 concomitant with its phosphorylation at Ser119 by protein kinase A (PKA). PDE4A11 differs from PDE4A4 in sensitivity to cleavage by caspase-3, interaction with LYN SH3 domain, redistribution upon long-term rolipram challenge, and sensitivity to certain PDE4 inhibitors. PDE4A11, PDE4A10, and PDE4A4 all can interact with betaarrestin. PDE4A11 is a novel, widely expressed long isoform that is activated by PKA phosphorylation and shows a distinct intracellular localization, indicating that it may contribute to compartmentalized cAMP signaling in cells in which it is expressed.