Molecular cloning of cAMP-dependent protein kinase catalytic subunit isoforms from the lone star tick, Amblyomma americanum (L.)

The salivary glands of ixodid ticks are central to tick feeding and to survival during off-host periods. They produce and secrete a number of molecules critical to maintaining the complex host-vector interface and to maintaining osmotic balance. We have previously shown that a cyclic AMP-dependent protein kinase (cAPK) is involved in the mechanism of salivary gland secretion. We have now cloned cDNAs encoding three isoforms of the catalytic subunit (cAPK-C) of the cAPK from Amblyomma americanum, which are probably produced from alternative RNA processing of a single cAPK-C gene. The cDNAs contain unique N-termini of variable lengths that are linked to a common region containing the alpha A helix, catalytic core, and a C-terminal tail. The common region is highly similar to both insect and vertebrate cAPK-Cs. We have examined mRNA profiles in whole ticks and in isolated salivary glands throughout feeding and find that a single cAPK-C isoform is expressed in the salivary glands of both unfed and feeding females.