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1 August 2000 A Novel Isoform of Human Cyclic 3′,5′-Adenosine Monophosphate-Dependent Protein Kinase, Cα-s, Localizes to Sperm Midpiece
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Abstract

Using rapid amplification of cDNA ends, a cDNA encoding a novel splice variant of the human Cα catalytic subunit of cAMP-dependent protein kinase (PKA) was identified. The novel isoform differed only in the N-terminal part of the deduced amino acid sequence, corresponding to the part encoded by exon 1 in the previously characterized murine Cα gene. Sequence comparison revealed similarity to an ovine Cα variant characterized by protein purification and micropeptide sequencing, Cα-s, identifying the cloned human cDNA as the Cα-s isoform. The Cα-s mRNA was expressed exclusively in human testis and expression in isolated human pachytene spermatocytes was demonstrated. The Cα-s protein was present in ejaculated human sperm, and immunofluorescent labeling with a Cα-s-specific antibody indicated that Cα-s was localized in the midpiece region of the spermatozoon. The majority of Cα-s was particulate and could not be released from the sperm midpiece by cAMP treatment alone. Furthermore, detergent extraction solubilized approximately two-thirds of the Cα-s pool, indicating interaction both with detergent-resistant cytoskeletal and membrane structures. In addition, we recently identified the regulatory subunit isoforms RIα, RIIα, and an A-kinase anchoring protein, hAKAP220 in this region in sperm that could target Cα-s. This novel Cα-s splice variant appeared to have an independent anchor in the human sperm midpiece as it could not be completely solubilized even in the presence of both detergent and cAMP.

Nils Reinton, Sigurd Ørstavik, Trine B. Haugen, Tore Jahnsen, Kjetil Taskén, and Bjørn S. Skålhegg "A Novel Isoform of Human Cyclic 3′,5′-Adenosine Monophosphate-Dependent Protein Kinase, Cα-s, Localizes to Sperm Midpiece," Biology of Reproduction 63(2), 607-611, (1 August 2000). https://doi.org/10.1095/biolreprod63.2.607
Received: 2 February 2000; Accepted: 1 April 2000; Published: 1 August 2000
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