title: Molecular characterisation of cAMP-dependent protein kinase (PK-A) catalytic subunit isoforms in the male tick, Amblyomma hebraeum.
abstract: The cAMP-dependent protein kinase (protein kinase A, PK-A) plays a central role in the regulation of diverse aspects of cellular activity. Specifically, PK-A appears to play a key controlling role in the maturation of spermatids. Using a PCR-based approach, with degenerate primers from the highly conserved regions of the PK-A catalytic (C) subunit in combination with 5' and 3' RACE, we have cloned three cDNAs for the PK-A C-subunit of the male tick, Amblyomma hebraeum. The three cDNAs have open reading frames of 1059, 1275 and 1404bp which encode proteins of 40.6, 48.2 and 52.5kDa, respectively. These transcripts appear to arise from 5' alternative splicing of RNA derived from a single gene for the PK-A C-subunit. One isoform (AH-PK-A C1), in common with PK-A C-subunits from a range of species, contains a consensus sequence for N-myristoylation. RT-PCR and Western blot experiments suggest that the three splice variants are expressed ubiquitously; however, expression of the myristoylatable AH-PK-A C1 isoform is predominant in all investigated tissues (accessory gland, midgut, Malpighian tubules, salivary gland, testis and immature spermatids). There is no evidence for a sperm-specific PK-A C-subunit (Cs) in tick sperm; however, tyrosine protein phosphorylation, previously shown to be modulated by PK-A activity during mammalian sperm maturation, was observed in tick sperm.
authors.affiliation: Cellular Regulation and Signalling Group, School of Biological Sciences, Biosciences Building, University of Liverpool, Crown Street, Liverpool L69 7ZB, UK.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Tabish
authors.forename: Roger A
authors.initials: RA
authors.lastname: Clegg
authors.forename: Philip C
authors.initials: PC
authors.lastname: Turner
authors.forename: Jan
authors.initials: J
authors.lastname: Jonczy
authors.forename: Huw H
authors.initials: HH
authors.lastname: Rees
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Fisher
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D020134:Catalytic Domain; D003001:Cloning, Molecular; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D018076:DNA, Complementary; D005260:Female; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D026863:Ixodidae / Q000201:enzymology*; D008297:Male; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010766:Phosphorylation; D017422:Sequence Analysis, DNA; D013087:Spermatids / Q000254:growth & development; D013091:Spermatogenesis
chemical_list: D018076:DNA, Complementary; D007527:Isoenzymes; D017868:Cyclic AMP-Dependent Protein Kinases