Submitted to: Insect Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2002
Publication Date: 2/1/2003
Citation: Holmes, S.P., Barhoumi, R., Nachman, R.J., Pietrantonio, P.V. 2003. Functional analysis of a G protein-coupled receptor from the southern cattle tick Boophilus microplus (Acari: Ixodidae) identifies it as the first arthropod myokinin receptor. Insect Molecular Biology. 12(1):27-38.
Interpretive Summary: Neuropeptides are short chains of amino acids (the building blocks of proteins) that regulate aspects of reproduction, development, water balance and digestion that are critical for insect and tick survival. Nevertheless, these neuropeptides in and of themselves hold little promise as pest control agents because of susceptibility to being degraded in the target pest, and inability to pass through the outside skin (cuticle) and/or digestive tract. We must design neuropeptide mimics that resist degradation by enzymes in the digestive tract and blood of pest insects and ticks and interact with the active site within the agricultural pest in such a way as to either over-activate or block critical, neuropeptide-regulated life functions. We report on the first isolation and characterization of the active site for the myokinin class of neuropeptides from an arthropod source, specifically from an important veterinary pest, the Southern cattle fever tick. This discovery will aid in the design of neuropeptide-like compounds capable of disrupting important neuropeptide-regulated processes in ticks and insects. The work brings us a step closer to the development of practical neuropeptide-like substances that will be effective in controlling agricultural pests in an environmentally friendly fashion.
Technical Abstract: The myokinins are invertebrate neuropeptides with myotropic and diuretic activity. The lymnokinin receptor from the snail Lymnaea stagnalis (Mollusca) has been the only previously identified myokinin receptor. We had cloned a G protein-coupled receptor (AF228521) from the tick Boophilus microplus (Arthropoda: Acari), 40% identical to the lymnokinin receptor, that we have now expressed in CHO-K1 cells. Myokinins at nanomolar concentrations induced intracellular calcium release, as measured by fluorescent cytometry and the receptor coupled to a pertussis toxin-insensitive G protein. Absence of extracellular calcium did not inhibit the fluorescence response. Control cells only transfected with vector did not respond. We conclude that the tick receptor is the first myokinin receptor to be cloned from an arthropod.