Chen AC

References (9)

Title : Acetylcholinesterase of Stomoxys calcitrans (L.) (Diptera: Muscidae): cDNA sequence, baculovirus expression, and biochemical properties - Temeyer_2012_Vet.Parasitol_184_92
Author(s) : Temeyer KB , Chen AC
Ref : Vet Parasitol , 184 :92 , 2012
Abstract : A 2193-nucleotide cDNA encoding acetylcholinesterase (AChE) of the stable fly, Stomoxys calcitrans (L.) was sequenced and expressed in the baculovirus system. The open reading frame encoded a 91 amino acid secretion signal peptide and a 613 amino acid mature protein with 96% and 94% identity to the AChEs of Haematobia irritans (L.) and Musca domestica (L.), respectively. Structural characteristics of M. domestica, H. irritans, and Drosophila melanogaster AChEs were conserved in the S. calcitrans AChE. The recombinant enzyme was inhibited by eserine, coroxon, and paraoxon and exhibited K(m) values of 63.9muM for acetylthiocholine and 96.7muM for butyrylthiocholine, confirming its biochemical identity as an acetylcholinesterase (EC 3.1.1.7). These data will enable rapid identification and assay for mutations that reduce AChE sensitivity to organophosphate (OP) pesticides, potentially aiding resistance management efforts to prevent fixation of the mutations in pest populations.
ESTHER : Temeyer_2012_Vet.Parasitol_184_92
PubMedSearch : Temeyer_2012_Vet.Parasitol_184_92
PubMedID: 21872994
Gene_locus related to this paper: stoca-ACHE

Title : A survey of Rhipicephalus microplus populations for mutations associated with pyrethroid resistance - Chen_2009_J.Econ.Entomol_102_373
Author(s) : Chen AC , He H , Temeyer KB , Jones S , Green P , Barker SC
Ref : J Econ Entomol , 102 :373 , 2009
Abstract : Mutations associated with pyrethroid resistance were found in Mexican strains of Rhipicephalus microplus (Canestrini). A mutation in the sodium channel gene was reported in strains highly resistant to permethrin and another mutation in an esterase gene in a strain that shows moderate resistance to the same pesticide. Methods based on the melting temperature difference of amplified allele-specific DNA fragments were developed that can detect these mutations rapidly in individual larvae. When these methods were applied to ticks from various strains of R. microplus from Australia, neither of these mutations could be demonstrated. Different resistance mechanisms have apparently developed independently between Australian and Mexican strains of R. microplus.
ESTHER : Chen_2009_J.Econ.Entomol_102_373
PubMedSearch : Chen_2009_J.Econ.Entomol_102_373
PubMedID: 19253657

Title : Acetylcholinesterase mutation in diazinon-resistant Haematobia irritans (L.) (Diptera: Muscidae) - Temeyer_2008_Vet.Parasitol_154_300
Author(s) : Temeyer KB , Li AY , Lohmeyer KH , Chen AC , Olafson PU , Sanson DW , Foil LD
Ref : Vet Parasitol , 154 :300 , 2008
Abstract : Acetylcholinesterase (AChE) cDNA from individual field-collected diazinon-resistant horn flies was amplified by RT-PCR. Sequencing of the amplification products revealed that 8/12 of the diazinon-resistant horn flies contained a point mutation previously associated with resistance to organophosphates in house flies and Drosophila, strongly suggesting that this cDNA encodes the AChE that is the target site for organophosphate (OP) pesticide. The point mutation (G262A) resulted in a shift from glycine to alanine in the mature HiAChE amino acid sequence at position 262. Allele-specific PCR and RLFP assays were developed to diagnose the presence or absence of the G262A mutation in individual flies. Use of the allele-specific assays each demonstrated the presence of the G262A mutation in 10 of 12 individual field-collected flies, demonstrating higher sensitivity than direct sequencing of RT-PCR amplification products. The G262A mutation was found in additional fly populations previously characterized as OP-resistant, further supporting that this AChE is the target site for OP pesticide. The allele-specific assay is a useful tool for quantitative assay of the resistance allele in horn fly populations.
ESTHER : Temeyer_2008_Vet.Parasitol_154_300
PubMedSearch : Temeyer_2008_Vet.Parasitol_154_300
PubMedID: 18472339
Gene_locus related to this paper: haeir-ACHE

Title : R86Q, a mutation in BmAChE3 yielding a Rhipicephalus microplus organophosphate-insensitive acetylcholinesterase - Temeyer_2007_J.Med.Entomol_44_1013
Author(s) : Temeyer KB , Pruett JH , Olafson PU , Chen AC
Ref : Journal of Medical Entomology , 44 :1013 , 2007
Abstract : Mutations were identified in the cDNA sequence encoding the acetylcholinesterase BmAChE3 in strains of Rhipicephalus (Boophilus) microplus (Canestrini) resistant or susceptible to organophosphate (OP) acaricide. The mutation that occurred most frequently in the OP-resistant San Roman strain resulted in a substitution of glutamine (Q) for arginine (R) at position 86 in BmAChE3 (position 66 in mature BmAChE). Clones containing the mutant and wild-type cDNA sequences were expressed in the baculovirus system. Enzyme kinetics of recombinant BmAChE3 containing or lacking the R86Q mutation demonstrated that the R86Q mutation increased substrate affinity and conferred insensitivity to paraoxon inhibition. This is the first demonstration of a mutation in a gene encoding an ixodid acetylcholinesterase resulting in OP insensitivity. A restriction fragment length polymorphism assay was developed and used to diagnose the frequency of the R86Q mutation in BmAChE3 genomic DNA from seven laboratory-colonized strains. Use of the R86Q diagnostic assay detected an increased frequency of the R86Q mutation in OP-resistant tick strains compared with that of OP-susceptible strains; however, the R86Q mutation was also present in OP-susceptible strains at unexpectedly high frequency. Because the R86Q mutation generates an OP-resistant enzyme in vitro and it is present at an elevated frequency in laboratory strains selected for OP resistance, we conclude that the data are consistent with a potential role for BmAChE3 in development of OP resistance; however, because the R86Q mutation has a high frequency in susceptible strains, the R86Q mutation alone is insufficient to generate the OP-resistant phenotype at the organismal level. There are likely to be additional mutations in BmAChE3, mutations in additional acetylcholinesterase genes, or additional resistance mechanisms (e.g., oxidative metabolism) that contribute to expression of the OP-resistant phenotype.
ESTHER : Temeyer_2007_J.Med.Entomol_44_1013
PubMedSearch : Temeyer_2007_J.Med.Entomol_44_1013
PubMedID: 18047200
Gene_locus related to this paper: boomi-ACHE3

Title : Identification and characterization of a cDNA encoding the acetylcholinesterase of Haematobia irritans (L.) (Diptera: Muscidae) - Temeyer_2007_DNA.Seq_18_85
Author(s) : Temeyer KB , Chen AC
Ref : DNA Sequence , 18 :85 , 2007
Abstract : A 2217-nucleotide cDNA presumptively encoding acetylcholinesterase (AChE) of the horn fly, Haematobia irritans (L.) was sequenced. The open reading frame (ORF) encoded a 91 amino acid secretion signal peptide and a 613 amino acid mature protein with 95% identity and 98% similarity to the AChE of Musca domestica (L.). Structural features characteristic of the M. domestica and Drosophila melanogaster AChEs are conserved in the H. irritans AChE. The M. domestica and D. melanogaster AChEs are target sites for organophosphate inhibition as previously shown (Walsh et al. 2001. Biochem. J. 359: 175-181, Kozaki et al. 2002. Appl. Entomol. Zool. 37: 213-218), suggesting that this H. irritans AChE2 may be the target site for organophosphate.
ESTHER : Temeyer_2007_DNA.Seq_18_85
PubMedSearch : Temeyer_2007_DNA.Seq_18_85
PubMedID: 17364819
Gene_locus related to this paper: haeir-ACHE

Title : Baculovirus expression of BmAChE3, a cDNA encoding an acetylcholinesterase of Boophilus microplus (Acari: Ixodidae) - Temeyer_2006_J.Med.Entomol_43_707
Author(s) : Temeyer KB , Pruett JH , Untalan PM , Chen AC
Ref : Journal of Medical Entomology , 43 :707 , 2006
Abstract : The complete cDNA sequence encoding a Boophilus microplus (Canestrini) (Acari: Ixodidae) acetylcholinesterase (AChE3) was expressed in the baculovirus system. The recombinant AChE3 protein (rBmAChE3) was secreted as a soluble form into the cell culture medium and was identified as a functional AChE by substrate specificity and by inhibition with the AChE-specific inhibitors eserine sulfate and BW284c51. Inhibition kinetics of rBmAChE3, in the presence of the organophosphate paraoxon, revealed sensitivity comparable with that of adult, organophosphate-susceptible neural AChE. To our knowledge, this is the first report of the cloning and successful expression of a functional ixodid AChE.
ESTHER : Temeyer_2006_J.Med.Entomol_43_707
PubMedSearch : Temeyer_2006_J.Med.Entomol_43_707
PubMedID: 16892628
Gene_locus related to this paper: boomi-ACHE3

Title : Identification of a third Boophilus microplus (Acari: Ixodidae) cDNA presumptively encoding an acetylcholinesterase - Temeyer_2004_J.Med.Entomol_41_259
Author(s) : Temeyer KB , Davey RB , Chen AC
Ref : Journal of Medical Entomology , 41 :259 , 2004
Abstract : Oligodeoxynucleotide primers, based on amino acid sequences conserved in known acetylcholinesterases (AChEs), were used in reverse-transcription polymerase chain reaction (RT-PCR) with mRNA from Boophilus microplus (Canestrini) as the template. Primer walking and rapid amplification of cDNA ends (RACE) techniques were used to complete the cDNA sequence identified by RT-PCR. The complete B. microplus cDNA sequence contained an open reading frame encoding a 620 amino acid protein with a 20 amino acid signal peptide at the N-terminus targeting the protein for the secretion pathway. BLAST searches of GenBank using the presumptively encoded protein revealed highest sequence similarity to AChEs. The presumptively encoded protein was of similar size and structural properties to other identified AChEs, including the presence of the catalytic triad (Ser, Glu, His) and appropriate placement of internal cysteines to yield three internal disulfide bonds corresponding to those of known AChEs. Putative conserved domains identified the sequence as a member of the carboxylesterase family, pfam00135.8, of which AChE is a member. This cDNA therefore presumptively encodes a third transcribed AChE (AChE3) cDNA of B. microplus. Comparison of the three AChE eDNA sequences expressed in B. microplus demonstrated no discernible nucleotide sequence homology and relatively low amino acid sequence homology, strongly suggesting that they are not alleles of one another. The potential presence of multiple expressed AChEs in B. microplus suggests alternative mechanisms for development of resistance to pesticides that target AChE. The homology-based identification of a third expressed AChE in B. microplus is a surprising result and strongly implies the need for confirmation of gene identity for presumptive AChEs.
ESTHER : Temeyer_2004_J.Med.Entomol_41_259
PubMedSearch : Temeyer_2004_J.Med.Entomol_41_259
PubMedID: 15185924
Gene_locus related to this paper: boomi-ACHE3

Title : Identification of a point mutation in an esterase gene in different populations of the southern cattle tick, Boophilus microplus - Hernandez_2000_Insect.Biochem.Mol.Biol_30_969
Author(s) : Hernandez R , He H , Chen AC , Waghela SD , Wayne Ivie G , George JE , Gale Wagner G
Ref : Insect Biochemistry & Molecular Biology , 30 :969 , 2000
Abstract : Two esterase cDNA sequences were obtained from susceptible and organophosphorus resistant strains of Boophilus microplus. Both sequences have a high degree of homology to carboxylesterase B. One gene has identical sequences in both strains and the other showed two point mutations. One mutation produces an amino acid substitution when the amino acid sequence is deduced, this mutation was detected in six different populations susceptible and resistant to insecticides, but a pyrethroid resistant strain was the only one that showed only the mutant allele. Identification of this mutation and the strong signal detected in southern blot with this strain, suggest that esterases are contributing to detoxification of pyrethroid compounds, as a resistant mechanism in Mexican strains of the southern cattle tick.
ESTHER : Hernandez_2000_Insect.Biochem.Mol.Biol_30_969
PubMedSearch : Hernandez_2000_Insect.Biochem.Mol.Biol_30_969
PubMedID: 10899463
Gene_locus related to this paper: boomi-este08 , boomi-este13

Title : Cloning and sequencing of a putative acetylcholinesterase cDNA from Boophilus microplus (Acari: Ixodidae) - Hernandez_1999_J.Med.Entomol_36_764
Author(s) : Hernandez R , He H , Chen AC , Ivie GW , George JE , Wagner GG
Ref : Journal of Medical Entomology , 36 :764 , 1999
Abstract : Using a strategy based on degenerate primers derived from acetylcholinesterase (AChE) from other species, we cloned and sequenced a putative AChE cDNA from the southern cattle tick, Boophilus microplus (Canestrini). The sequence has a high degree of homology to sequences of AChE from other species reported in the GenBank. The open reading frame of 1,689 bp, corresponding to a deduced sequence of 563 amino acids, has conserved regions and features shared by the AChE family, necessary for its catalytic activity. No differences were found in the putative cDNA sequences from organophosphorus acaricide (OP) resistant and susceptible strains. The results suggest that this putative AChE gene is not involved in resistance to OP compounds as a mutated gene in the resistant strain studied. However, differences were detected, with a probe derived from this cDNA, in DNA fragments after digestion of genomic DNA from different strains with restriction nucleases. This indicates polymorphism in this gene in B. microplus.
ESTHER : Hernandez_1999_J.Med.Entomol_36_764
PubMedSearch : Hernandez_1999_J.Med.Entomol_36_764
PubMedID: 10593078
Gene_locus related to this paper: boomi-ACHE2