Methods for using 22045, a human cyclic nucleotide phosphodiesterase

#The present invention relates to methods for using a human cyclic nucleotide phosphodiesterase. The invention also relates to methods for using polynucleotides encoding the phosphodiesterase. The invention further relates to methods using the phosphodiesterase polypeptides and polynucleotides as a target for diagnosis and treatment in phosphodiesterase-mediated or -related disorders. The invention further relates to drug-screening methods using the phosphodiesterase polypeptides and polynucleotides to identify agonists and antagonists for diagnosis and treatment. The invention further encompasses agonists and antagonists based on the phosphodiesterase polypeptides and polynucleotides. The invention further relates to agonists and antagonists identified by drug screening methods with the phosphodiesterase polypeptides and polynucleotides as a target.

#Cyclic nucleotide phosphodiesterases show specificity for purine cyclic nucleotide substrates and catalyze cyclic AMP (cAMP) and cyclic GMP (cGMP) hydrolysis (Thompson W. J. (1991) Pharma. Ther. 51:13-33). Cyclic nucleotide phosphodiesterases regulate the steady-state levels of cAMP and cGMP and modulate both the amplitude and duration of cyclic nucleotide signal. At least eight different but homologous gene families are currently known to exist in mammalian tissues. Most families contain distinct genes, many of which are expressed in different tissues as functionally unique alternative splice variants (Beavo (1995) Physiological Reviews 75:725-748 and U.S. Pat. No. 5,798,246).

#All cyclic nucleotide phosphodiesterases contain a core of about 270 conserved amino acids in the COOH-terminal half of the protein thought to be the catalytic domain of the enzyme. A conserved motif of the sequence HDXXHXX has been identified in the catalytic domain of all cyclic nucleotide phosphodiesterases isolated to date. The cyclic nucleotide phosphodiesterases within each family display about 65% amino acid homology and the similarity drops to less than 40% when compared between different families with most of the similarity occurring in the catalytic domains.

#FIGS. 1A-C show the phosphodiesterase nucleotide sequence (SEQ ID NO 2) and the deduced amino acid sequence (SEQ ID NO 1). BLAST analysis showed the top BLAST scores to AB020593, AF127479, AF127480 human dual specificity cAMP/cGMP, and mouse PDE10A, AF110507. AF110507, AF127480, AF127479, AB020593=GenBank accession. See, for example, Sonderling, et al., Proc. Natl'l. Acad. Sci. U.S.A. 96:7071-7076 (1999).

#FIG. 2 shows a hydrophobicity plot of the phosphodiesterase.

#FIG. 3 shows an analysis of the phosphodiesterase amino acid sequence: αβturn and coil regions; hydrophilicity; amphipathic regions; flexible regions; antigenic index; and surface probability plot.

#As used herein, a “signaling pathway” refers to the modulation (e.g., stimulation or inhibition) of a cellular function/activity upon the binding of a ligand to a receptor. Examples of such functions include mobilization of intracellular molecules that participate in a signal transduction pathway, e.g., phosphatidylinositol 4,5-bisphosphate (PIP2), inositol 1,4,5-triphosphate (IP3) and adenylate cyclase; polarization of the plasma membrane; production or secretion of molecules; alteration in the structure of a cellular component; cell proliferation, e.g., synthesis of DNA; cell migration; cell differentiation; and cell survival.

#The response depends on the type of cell. In some cells, binding of a ligand to the receptor may stimulate an activity such as release of compounds, gating of a channel, cellular adhesion, migration, differentiation, etc., through phosphatidylinositol or cyclic AMP metabolism and turnover while in other cells, binding will produce a different result.

#The cAMP turnover pathway is a signaling pathway. As used herein, “cyclic AMP turnover and metabolism” refers to the molecules involved in the turnover and metabolism of cAMP as well as to the activities of these molecules. Cyclic AMP is a second messenger produced in response to ligand-induced stimulation of certain receptors. In the cAMP signaling pathway, binding of a ligand can lead to the activation of the enzyme adenyl cyclase, which catalyzes the synthesis of cAMP. The newly synthesized cAMP can in turn activate a cAMP-dependent protein kinase. This activated kinase can phosphorylate a voltage-gated potassium channel protein, or an associated protein, and lead to the inability of the potassium channel to open during an action potential. The inability of the potassium channel to open results in a decrease in the outward flow of potassium, which normally repolarizes the membrane of a neuron, leading to prolonged membrane depolarization.