Soluble expression in Escherichia coli of active human cyclic nucleotide phosphodiesterase isoform 4B2 in fusion with maltose-binding protein.

Recombinant expression in Escherichia coli of human cyclic nucleotide phosphodiesterase 4B2 (hPDE4B2) fused to maltose-binding-protein (MBP-hPDE4B2) was investigated. hPDE4B2 DNA amplified via nested RT-PCR with total RNAs from U937 cells was ligated with pMAL-p2x. After induction at 18 degrees C for 16 h, soluble MBP-hPDE4B2 was produced in E. coli. MBP-hPDE4B2 after amylose-resin chromatography showed 35% homogeneity, and its Michaelis-Menten constant was 10+/-2 microM (n=3). Rolipram had a dissociation constant of 9+/-2 nM (n=2), and zinc ion was a potent inhibitor. Hence, MBP-hPDE4B2 was expressed in E. coli as a soluble active protein.

Human PDE4A8, a novel brain-expressed PDE4 cAMP-specific phosphodiesterase that has undergone rapid evolutionary change.

We have isolated cDNAs encoding PDE4A8 (phosphodiesterase 4 isoform A8), a new human cAMP-specific PDE4 isoform encoded by the PDE4A gene. PDE4A8 has a novel N-terminal region of 85 amino acids that differs from those of the related 'long' PDE4A4, PDE4A10 and PDE4A11 isoforms. The human PDE4A8 N-terminal region has diverged substantially from the corresponding isoforms in the rat and other mammals, consistent with rapid evolutionary change in this region of the protein. When expressed in COS-7 cells, PDE4A8 localized predominantly in the cytosol, but approx. 20% of the enzyme was associated with membrane fractions. Cytosolic PDE4A8 was exquisitely sensitive to inhibition by the prototypical PDE4 inhibitor rolipram (IC(50) of 11+/-1 nM compared with 1600 nM for PDE4A4), but was less sensitive to inhibition by cilomilast (IC(50) of 101+/-7 nM compared with 61 nM for PDE4A4). PDE4A8 mRNA was found to be expressed predominantly in skeletal muscle and brain, a pattern that differs from the tissue expression of other human PDE4 isoforms and also from that of rat PDE4A8. Immunohistochemical analysis showed that PDE4A8 could be detected in discrete regions of human brain, including the cerebellum, spinal cord and cerebral cortex. The unique tissue distribution of PDE4A8, combined with the evolutionary divergence of its N-terminus, suggest that this isoform may have a specific function in regulating cAMP levels in human skeletal muscle and brain.

Ultrasound Assisted One-pot and Sequential Synthesis of 3-methylene-isoindolin-1-ones and their in vitro Evaluation.

BACKGROUND: 3-Methyleneisoindolin-1-one derivatives containing a pyridin-2-ylmethyl substituent on their ring nitrogen were designed as potential bioactive agents. A one-pot synthesis of these compounds was achieved via sequential C-C coupling, followed by C-Si bond cleavage and subsequent tandem C-C/C-N bond forming reaction under ultrasound irradiation. METHOD: The methodology involved coupling of (trimethylsilyl)acetylene with iodoarenes in the presence of 10% Pd/C-CuI-PPh3-Et3N in MeOH followed by treating the reaction mixture with K2CO3 in aqueous MeOH, and finally coupling with 2-iodo-N-(pyridin-2-ylmethyl)benzamide. The in vitro evaluation of these compounds was performed to identify some initial hit molecules one of which showed dose dependent inhibition of PDE4B.

Production and characterization of pharmacologically active recombinant human phosphodiesterase 4B in Dictyostelium discoideum.

Phosphodiesterase 4B (PDE4B) is an important therapeutic target for asthma and chronic obstructive pulmonary disease. To identify PDE4 subtype-specific compounds using high-throughput assays, full-length recombinant PDE4 proteins are needed in bulk quantity. In the present study, full-length human PDE4B2 was expressed in the cellular slime mould Dictyostelium discoideum (Dd). A cell density of 2 x 10(7) cells/mL was obtained and up to 1 mg/L recombinant PDE4B2 was purified through Ni-NTA affinity chromatography. The expressed protein was soluble and its activity was comparable to PDE4B2 protein expressed in mammalian cells (K(m)=1.7 microM). The functional significance of the Dd expression system is supported by the demonstration that, in concert with proteins expressed in mammalian systems, there are no major changes in the affinity for PDE4B2 inhibitors and substrates. These findings thus provide the first evidence that Dd can be utilized for the expression and purification of functionally active full-length human PDE4B2 in large amounts required for high-throughput screening of pharmacologically active compounds against this therapeutic target.

Expression profiles of phosphodiesterase 4D splicing variants in osteoblastic cells.

The promotion of osteoblastic differentiation by bone morphogenetic proteins (BMPs) is accelerated by chemical compounds that increase the intracellular concentration of cyclic 3',5'-adenosine monophosphate (cAMP). cAMP is synthesized from adenosine triphosphate (ATP) by adenyl cyclase and degraded by phosphodiesterase (PDE) family enzymes. Inhibition of PDEs leads to prolonged accumulation of cAMP within cells and Camp-mediated reactions. Rolipram, a specific inhibitor of PDE4, is a compound effective in inducing osteoblastic differentiation. Four PDE4 family members are transcribed from four distinct genes (4A, 4B, 4C, and 4D). Expression of PDE4A and PDE4D has been observed in osteoblastic cells. We identified PDE4D splicing variants that expressed in ST2 or primary calvarial osteoblasts by rapid amplification of the 5'-ends of cDNA when they were cultured with BMP. PDE4D9 mRNA was identified from ST2, and PDE4D1 and -4D2 mRNAs were identified from primary calvarial osteoblasts. Expression of these three variants of PDE4D mRNA was found in ST2, MC3T3-E1, C3H10T1/2, C2C12, and primary calvarial osteoblasts by RT-PCR, but not PDE4D1 or -4D2 in ST2 or PDE4D2 in MC3T3-E1. Expression of these three variants was detectable in brain, heart, lung, liver, kidney, placenta, and femur, and was thus ubiquitous. Purified recombinant PDE4D9 protein exhibited phosphodiesterase activity, which degraded cAMP to AMP, and this activity was inhibited by rolipram. These findings suggest that PDE4D1, -2, and -9 play some roles in bone formation.

Assays for cyclic nucleotide-specific phosphodiesterases (PDEs) in the central nervous system (PDE1, PDE2, PDE4, and PDE10).

Since the identification of phosphodiesterase activity in brain tissue more than 40 years ago, 11 distinct gene families have been identified, differing with respect to localization, regulation, affinity for cAMP and cGMP, and distinct functions within cells. PDEs 1, 2, 4, and 10 are currently of special interest to CNS pharmacology because of their high expression in specific areas of the brain and the behavioral effects of inhibitors of these enzymes in rodents. Efficient high-throughput PDE enzyme assays are essential for PDE-targeted drug discovery, and this unit details two types of assays. The first method is relatively inexpensive and is based on separating radiolabeled cNMPs from degradation products on alumina columns. The second method is fluorescence-based; it is fast and better accommodates high-throughput screening, but is more expensive. Although these methods have successfully been used for PDEs 1, 2, 4 and 10, they could be readily adapted to other PDEs.