Studies on the Expressions of Caenorhabditis elegans K+ Channels and nACh Receptors in Xenopus oocytes
Okuniewski, Diana E.
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The effectiveness of drugs used to treat diseases caused by gastrointestinal nematodes has diminished due to the proliferation of strains resistant to the currently marketed anthelmintics. Oxindole alkaloid compounds (paraherquamide/marcfortine family) however, are one of the new classes of anthelmintic reported since the introduction of the macrocyclic lactones. These drugs are broad-spectrum anthelmintics that even affect many drug-resistant strains of nematodes (Zinser, 2001). Our study was designed to investigate the mechanism of action of oxindole alkaloid compounds using the Xenopus oocyte system. We used the oocyte system to express a nicotinic acetylcholine receptor (nAChR), unc-3%, which we cloned from the free-living nematode, Caenorhabditis elegans. In order to facilitate expression of this receptor, we also included perfusion with PNU-141962 (2-deoxoparaherquamide) in an effort to study the drug's pharmacology. Secondly, we tested the six amino acid modification, FCYENE (export signal), to determine if it is effective in increasing expression of CeK+ channels in oocytes, and to help determine if this segment can be used to increase expression of any type of gene. Minimal expression was observed of the CeKl channel by itself. Additionally, the CeKl+FCYENE modification did not improve CeKl expression, suggesting that FCYENE may not be a useful export signal in the Xenopus oocyte system for nematodal receptors even though it has been found to enhance expression for mammalian receptors (Mae/ al, 2001).