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Identification of a New Variant of PDE1A Calmodulin-Stimulated Cyclic Nucleotide Phosphodiesterase Expressed in Mouse Sperm¹

Department of Pharmacology, University of Washington, Seattle, Washington 98195

In mature sperm, cAMP plays an important role as a second messenger regulating functions that include capacitation, the acrosome reaction, motility, and, in some cases, chemosensing. We have cloned from mouse testis a novel calmodulin-stimulated cyclic nucleotide phosphodiesterase 1A isoform, Pde1a_v7 (mmPDE1A7), which arises from an alternative transcription start in the cyclic nucleotide phosphodiesterase 1A gene. The open reading frame is predicted to encode a polypeptide with a molecular mass of 52 kDa. Two further variants of this form, which contain two additional new exons, arise from alternative splicing. Analysis of testis cDNA by real-time polymerase chain reaction (PCR) indicates that the Pde1A_v7 transcript variant is the most abundant. The PDE1A_v7 protein uniquely lacks the first amino-terminal calmodulin-binding domain, but does possess an inhibitory domain and a second calmodulin-binding site shared with other variants. In vitro translation of the corresponding Pde1a_v7 cDNA produced a 52-kDa polypeptide having cyclic nucleotide hydrolytic activity, which was stimulated threefold by calcium-bound calmodulin. Immunoprecipitation of cyclic nucleotide phosphodiesterase 1 activity from detergent extracts of mouse sperm revealed a major protein of the size expected for PDE1A_v7, and the immunocytochemical staining for cyclic nucleotide phosphodiesterase 1A in mouse sperm showed intense immunoreactivity in the tail only. These observations, along with the PCR data, strongly suggest that this new variant PDE1A_v7 is the major form of cyclic nucleotide phosphodiesterase 1A expressed in mature sperm and is therefore likely to play an important role in cyclic nucleotide regulation of mature sperm function.

calcium, signal transduction, sperm capacitation, sperm maturation, sperm motility and transport

² Correspondence: Joseph A. Beavo, University of Washington, Department of Pharmacology, Box 357280, 1959 NE Pacific St., Seattle, WA 98195. FAX: 206 685 3822; beavo{at}u.washington.edu

³ These authors contributed equally to this work

⁴ Current address: Lexicon Genetics Inc. 8800 Technology Forest Place, The Woodlands, TX 77381-1160

⁵ Current address: University of Rochester Medical Center, Cardiology Unit, Box 679, 601 Elmwood Ave., Rochester, NY 14642

⁶ Current address: Vollum Institute, Oregon Health Sciences University, 3181 Sam Jackson Park Road, Portland, Oregon 97239-3098

This article has been cited by other articles:

				A. T. Bender and J. A. Beavo Cyclic Nucleotide Phosphodiesterases: Molecular Regulation to Clinical Use Pharmacol. Rev., September 1, 2006; 58(3): 488 - 520. [Abstract] [Full Text] [PDF]