Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

Using a bioinformatic approach, we have identified two novel isozymes of human 3',5'-cyclic nucleotide phosphodiesterase (PDE), which we designated PDE8A and PDE8B. Both isozymes show 20 to 35% identity to the known human PDEs limited in the catalytic domain. The mRNA encoding PDE8A is expressed in a number of tissues and cancer cell lines and a smaller transcript was expressed specifically in the human colon rectal carcinoma cell SW480. On the contrary, the mRNA encoding PDE8B is expressed specifically and abundantly in thyroid gland. The carboxyl-terminal 584 amino acids of PDE8B were expressed in E.coli as a fusion protein. The recombinant PDE8B exhibited cAMP PDE activity which was not inhibited by various PDE inhibitors including vinpocetine, milrinone, rolipram, and IBMX with the exception of dipyridamole which caused 50% inhibition at a concentration of 40 µM. cAMP hydrolytic activity was unaffected by cGMP and no cGMP PDE hydrolysis were detectable at concentrations up to 100 µM. These findings suggest that these two isozymes are members of the new PDE family, PDE8.

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Poster Number PAhayashi0585
Keywords: phosphodiesterase, cyclic nucleotide