Sub‐family selective actions in the ability of Erk2 MAP kinase to phosphorylate and regulate the activity of PDE4 cyclic AMP‐specific phosphodiesterases

Abstract

1 Expressed in intact cells and in vitro, PDE4B and PDE4C isoenzymes of cyclic nucleotide phosphodiesterase (PDE), in common with PDE4D isoenzymes, are shown to provide substrates for C-terminal catalytic unit phosphorylation by the extracellular signal-regulated kinase Erk2 (p42 MAPK ). 2 In contrast, PDE4A isoenzymes do not provide substrates for C-terminal catalytic unit phosphorylation by Erk2. 3 Mutant PDE4 enzymes were generated to show that Erk2 phosphorylation occurs at a single, cognate serine residue located within the C-terminal portion of the PDE4 catalytic unit. 4 PDE4 long-form isoenzymes were markedly inhibited by Erk2 phosphorylation. 5 The short-form PDE4B2 isoenzyme was activated by Erk2 phosphorylation. 6 These functional changes in PDE activity were mimicked by mutation of the target serine for Erk2 phosphorylation to the negatively charged amino acid, aspartic acid. 7 Epidermal growth factor (EGF) challenge caused diametrically opposed changes in cyclic AMP levels in COS1 cells transfected to express the long PDE4B1 isoenzyme compared to cells expressing the short PDE4B2 isoenzyme. 8 We suggest that PDE4 enzymes may provide a pivotal point for integrating cyclic AMP and Erk signal transduction in cells with 4 genes encoding enzymes that are either insensitive to Erk2 action or may either be activated or inhibited. This indicates that PDE4 isoenzymes have distinct functional roles, giving credence to the notion that distinct therapeutic bene®ts may accrue using either PDE4 subfamily or isoenzyme-selective inhibitors.

RETRACTED: β-Arrestin-mediated PDE4 cAMP phosphodiesterase recruitment regulates β-adrenoceptor switching from G s to G i

“…The PDE4D4-specific antiserum used was as described (25). mAbs (New England Biolabs) were used to detect the native and phosphorylated forms of ERK1͞2 as described (26)(27)(28). A phospho-serine PKA substrate antibody (Cell Signaling Technologies, Beverly, MA) was used to detect PKA phosphorylation of the ␤ 2 AR.…”

“…A rabbit polyclonal antiserum specific for the ␤ 2 AR was obtained from Santa Cruz Biotechnology (Autogen Bioclear, Wittshire, U.K.). Immunoblotting was done as described (26)(27)(28) by using Ϸ20-g protein samples. For immunopurification, cells were harvested in lysis buffer (25 mM Hepes͞2.5 mM EDTA͞50 mM NaC1͞50 mM NaF͞30 mM sodium pyrophosphate͞10% glycerol͞1% Triton X-100, pH 7.5, with added protease inhibitors) after specified treatments.…”

Vascular Smooth Muscle Cell Phenotype-Dependent Phosphodiesterase 4D Short Form Expression: Role of Differential Histone Acetylation on cAMP-Regulated Function

“…In addition to an obvious effect on cAMP-signaling, our data identifying differential up-regulation of long and short forms of PDE4D may also have broader consequences on VSMC signaling. Indeed, an important role for "cross-talk" between ERK and PDE4D activities was recently reported to markedly influence cellular responses to both cAMP-dependent and non-cAMP-dependent agents (Hoffmann et al, 1999;Liu and Maurice, 1999;Baillie et al, 2000;Baillie et al, 2001) and expression . Indeed, taken together, these reports are consistent with the idea that ERK-mediated phosphorylation inhibits PDE4D long forms (PDE4D3 and PDE4D5), and, in fact, can translocate particulate PDE4D3 away from its targeted membrane fraction to the cytosol, but activates PDE4D short forms (PDE4D1 and PDE4D2).…”

“…In addition to affecting PDE4D expression, PKA and ERKs also regulate PDE4D catalytic activity (Houslay and Adams, 2003;Maurice et al, 2003). Thus, although phosphorylation of PDE4D long forms by PKA activates these enzymes, ERK-mediated phosphorylation of the long and short PDE4Ds has form-specific effects on their activities (Baillie et al, 2000;Houslay and Adams, 2003). PKA phosphorylation of some long-form PDE4D variants also regulates their ability to associate with various scaffolding/anchoring proteins (for review, see Wong and Scott, 2004).…”

The DISC locus in psychiatric illness

“…Further potential intricacy is added by observations that reduction of DISC1 expression using RNA interference results in reduced levels of active extracellular signal-related kinase (ERK) in cultured rat cortical neurons 27 and at axonal growth cones of neurotrophin-treated cultured rat hippocampal neurons, 87 which may in turn influence PDE4 activity, because ERK phosphorylates, and regulates the activity of, the PDE4 catalytic domain. 137 It is clear that the function of DISC1/PDE4 complexes is likely to be elaborately regulated at many levels and, since both DISC1 and PDE4B have been independently identified as risk factors for major mental illness, it is possible that disturbance of any aspect of this interaction may be an important factor in the aetiology of disorders such as schizophrenia. It remains to be seen how much of PDE4 function involves DISC1, but since DISC1 contains five separate contact sites for PDE4B, of which four encompass a large proportion of the N-terminal head domain (Murdoch et al, in press), it is likely that DISC1 function is closely tied up with that of PDE4B.…”