ERG11 Polymorphism in Voriconazole-Resistant Candida tropicalis: Weak Role of ERG11 Expression, Ergosterol Content, and Membrane Permeability

ABSTRACTMutations in ERG11 were detected by gene sequencing and amino acid alignment in 18 Candida tropicalis strains with different degrees of sensitivity to voriconazole (VRC). ERG11 expression, sterol content, and membrane permeability were also evaluated. We report three missense mutations in ERG11 that resulted in resistance to VRC. The transcriptional levels of ERG11 as well as the ergosterol content and membrane permeability demonstrated no correlation to only a slight correlation with the obtained MIC values, but the data did suggest a tendency toward such a correlation.

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A Novel Role of Fungal Type I Myosin in Regulating Membrane Properties and Its Association with D-Amino Acid Utilization in Cryptococcus gattii

mBio ◽

10.1128/mbio.01867-19 ◽

2019 ◽

Vol 10 (4) ◽

Cited By ~ 3

Author(s):

Ami Khanal Lamichhane ◽

H. Martin Garraffo ◽

Hongyi Cai ◽

Peter J. Walter ◽

Kyung J. Kwon-Chung ◽

...

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Membrane Permeability ◽

Cryptococcus Gattii ◽

Membrane Properties ◽

Type I ◽

Content Type ◽

Myosin I ◽

Amino Acid Utilization

ABSTRACT We found a novel role of Myo5, a type I myosin (myosin-I), and its fortuitous association with d-amino acid utilization in Cryptococcus gattii. Myo5 colocalized with actin cortical patches and was required for endocytosis. Interestingly, the myo5Δ mutant accumulated high levels of d-proline and d-alanine which caused toxicity in C. gattii cells. The myo5Δ mutant also accumulated a large set of substrates, such as membrane-permeant as well as non-membrane-permeant dyes, l-proline, l-alanine, and flucytosine intracellularly. Furthermore, the efflux rate of fluorescein was significantly increased in the myo5Δ mutant. Importantly, the endocytic defect of the myo5Δ mutant did not affect the localization of the proline permease and flucytosine transporter. These data indicate that the substrate accumulation phenotype is not solely due to a defect in endocytosis, but the membrane properties may have been altered in the myo5Δ mutant. Consistent with this, the sterol staining pattern of the myo5Δ mutant was different from that of the wild type, and the mutant was hypersensitive to amphotericin B. It appears that the changes in sterol distribution may have caused altered membrane permeability in the myo5Δ mutant, allowing increased accumulation of substrate. Moreover, myosin-I mutants generated in several other yeast species displayed a similar substrate accumulation phenotype. Thus, fungal type I myosin appears to play an important role in regulating membrane permeability. Although the substrate accumulation phenotype was detected in strains with mutations in the genes involved in actin nucleation, the phenotype was not shared in all endocytic mutants, indicating a complicated relationship between substrate accumulation and endocytosis. IMPORTANCE Cryptococcus gattii, one of the etiological agents of cryptococcosis, can be distinguished from its sister species Cryptococcus neoformans by growth on d-amino acids. C. gattii MYO5 affected the growth of C. gattii on d-amino acids. The myo5Δ cells accumulated high levels of various substrates from outside the cells, and excessively accumulated d-amino acids appeared to have caused toxicity in the myo5Δ cells. We provide evidence on the alteration of membrane properties in the myo5Δ mutants. Additionally, alteration in the myo5Δ membrane permeability causing higher substrate accumulation is associated with the changes in the sterol distribution. Furthermore, myosin-I in three other yeasts also manifested a similar role in substrate accumulation. Thus, while fungal myosin-I may function as a classical myosin-I, it has hitherto unknown additional roles in regulating membrane permeability. Since deletion of fungal myosin-I causes significantly elevated susceptibility to multiple antifungal drugs, it could serve as an effective target for augmentation of fungal therapy.

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Genetic Basis forIn VitroandIn VivoResistance to Lincosamides, Streptogramins A, and Pleuromutilins (LSAP Phenotype) in Enterococcus faecium

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01030-13 ◽

2013 ◽

Vol 57 (9) ◽

pp. 4463-4469 ◽

Cited By ~ 28

Author(s):

Christophe Isnard ◽

Brigitte Malbruny ◽

Roland Leclercq ◽

Vincent Cattoir

Keyword(s):

Amino Acid ◽

Molecular Mechanism ◽

Enterococcus Faecium ◽

Full Genome Sequence ◽

Comparative Genomic ◽

Content Type ◽

Abc Protein

ABSTRACTAs opposed toEnterococcus faecalis, which is intrinsically resistant to lincosamides, streptogramins A, and pleuromutilins (LSAP phenotype) by production of the ABC protein Lsa(A),Enterococcus faeciumis naturally susceptible. Since this phenotype may be selected forin vivoby quinupristin-dalfopristin (Q-D), the aim of this study was to investigate the molecular mechanism of acquired LSAP resistance inE. faecium. Six LSAP-resistantin vitromutants ofE. faeciumHM1070 as well as three different pairs of clinical isolates (pre- and postexposure to Q-D) were studied. The full genome sequence of anin vitromutant (E. faeciumUCN90B) was determined by using 454 sequencing technology and was compared with that of the parental strain. Single-nucleotide replacement was carried out to confirm the role of this mutation. By comparative genomic analysis, a point mutation was found within a 1,503-bp gene coding for an ABC homologue showing 66% amino acid identity with Lsa(A). This mutation (C1349T) led to an amino acid substitution (Thr450Ile). An identical mutation was identified in allin vitroandin vivoresistant strains but was not present in susceptible strains. The wild-type allele was namedeat(A) (forEnterococcusABCtransporter), and its mutated allelic variant was namedeat(A)v. The introduction ofeat(A)vfrom UCN90B into HM1070 conferred the LSAP phenotype, whereas that ofeat(A) from HM1070 into UCN90B restored susceptibility entirely. This is the first description of the molecular mechanism of acquired LSAP resistance inE. faecium. Characterization of the biochemical mechanism of resistance and the physiological role of this ABC protein need further investigations.

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Amino Acid Substitutions of CrrB Responsible for Resistance to Colistin through CrrC in Klebsiella pneumoniae

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00009-16 ◽

2016 ◽

Vol 60 (6) ◽

pp. 3709-3716 ◽

Cited By ~ 49

Author(s):

Yi-Hsiang Cheng ◽

Tzu-Lung Lin ◽

Yi-Tsung Lin ◽

Jin-Town Wang

Keyword(s):

Amino Acid ◽

Klebsiella Pneumoniae ◽

Site Directed Mutagenesis ◽

Amino Acid Substitutions ◽

Missense Mutations ◽

Colistin Resistance ◽

Two Component System ◽

Content Type ◽

Carbapenem Resistant ◽

Elevated Expression

Colistin is a last-resort antibiotic for treatment of carbapenem-resistantKlebsiella pneumoniae. A recent study indicated that missense mutations in the CrrB protein contribute to colistin resistance. In our previous study, mechanisms of colistin resistance were defined in 17 of 26 colistin-resistantK. pneumoniaeclinical isolates. Of the remaining nine strains, eight were highly resistant to colistin. In the present study,crrABsequences were determined for these eight strains. Six separate amino acid substitutions in CrrB (Q10L, Y31H, W140R, N141I, P151S, and S195N) were detected. Site-directed mutagenesis was used to generatecrrBloci harboring individual missense mutations; introduction of the mutated genes into a susceptible strain, A4528, resulted in 64- to 1,024-fold increases in colistin MICs. ThesecrrBmutants showed increased accumulation ofH239_3062,H239_3059,pmrA,pmrC, andpmrHtranscripts by quantitative reverse transcription (qRT)-PCR. Deletion ofH239_3062(but not that ofH239_3059) in the A4528crrB(N141I) strain attenuated resistance to colistin, andH239_3062was accordingly namedcrrC. Similarly, accumulation ofpmrA,pmrC, andpmrHtranscripts induced bycrrB(N141I) was significantly attenuated upon deletion ofcrrC. Complementation ofcrrCrestored resistance to colistin and accumulation ofpmrA,pmrC, andpmrHtranscripts in acrrB(N141I) ΔcrrCstrain. In conclusion, novel individual CrrB amino acid substitutions (Y31H, W140R, N141I, P151S, and S195N) were shown to be responsible for colistin resistance. We hypothesize that CrrB mutations induce CrrC expression, thereby inducing elevated expression of thepmrHFIJKLMoperon andpmrC(an effect mediated via the PmrAB two-component system) and yielding increased colistin resistance.

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Imipenem plus Fosfomycin as Salvage Therapy for Vertebral Osteomyelitis

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01746-20 ◽

2020 ◽

Vol 65 (1) ◽

pp. e01746-20 ◽

Cited By ~ 1

Author(s):

Itaru Nakamura ◽

Tetsuo Yamaguchi ◽

Kotaro Aoki ◽

Yuri Miura ◽

Satoko Sato ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Amino Acid ◽

Antibiotic Therapy ◽

Combination Treatment ◽

Psoas Abscess ◽

Synergistic Effects ◽

Vertebral Osteomyelitis ◽

Gene Sequencing ◽

Content Type ◽

Synergy Test

ABSTRACTWe applied combination antibiotic therapy to treat vertebral osteomyelitis and a psoas abscess caused by glycopeptide-intermediate (MIC, 2 μg/ml) and daptomycin-nonsusceptible (>2 μg/ml) methicillin-resistant Staphylococcus aureus. The Etest synergy test showed the largest synergistic effects for imipenem/cilastatin and fosfomycin. Whole-gene sequencing showed amino acid changes in SA0802, SA1193 (mprF), and SA1531 (ald). Four weeks of combination treatment using imipenem/cilastatin (1.5 g per day) and fosfomycin (4.0 g per day) resulted in clinical improvement.

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Resistance Mechanisms and Clinical Features of Fluconazole-Nonsusceptible Candida tropicalis Isolates Compared with Fluconazole-Less-Susceptible Isolates

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02652-15 ◽

2016 ◽

Vol 60 (6) ◽

pp. 3653-3661 ◽

Cited By ~ 27

Author(s):

Min Ji Choi ◽

Eun Jeong Won ◽

Jong Hee Shin ◽

Soo Hyun Kim ◽

Wee-Gyo Lee ◽

...

Keyword(s):

Amino Acid ◽

Clinical Features ◽

Candida Tropicalis ◽

Resistance Mechanisms ◽

Therapeutic Failure ◽

Clinical Isolates ◽

Azole Resistance ◽

Amino Acid Substitutions ◽

Content Type ◽

Expression Levels

We investigated the azole resistance mechanisms and clinical features of fluconazole-nonsusceptible (FNS) isolates ofCandida tropicalisrecovered from Korean surveillance cultures in comparison with fluconazole-less-susceptible (FLS) isolates. Thirty-five clinical isolates ofC. tropicalis, comprising 9 FNS (fluconazole MIC, 4 to 64 μg/ml), 12 FLS (MIC, 1 to 2 μg/ml), and 14 control (MIC, 0.125 to 0.5 μg/ml) isolates, were assessed.CDR1,MDR1, andERG11expression was quantified, and theERG11andUPC2genes were sequenced. Clinical features of 16 patients with FNS or FLS bloodstream isolates were analyzed. Both FNS and FLS isolates had >10-fold higher mean expression levels ofCDR1,MDR1, andERG11genes than control isolates (Pvalues of <0.02 for all). When FNS and FLS isolates were compared, FNS isolates had 3.4-fold higher meanERG11expression levels than FLS isolates (P= 0.004), but there were no differences in those ofCDR1orMDR1. Of all 35 isolates, 4 (2 FNS and 2 FLS) and 28 (8 FNS, 11 FLS, and 9 control) isolates exhibited amino acid substitutions in Erg11p and Upc2p, respectively. Both FNS and FLS bloodstream isolates were associated with azole therapeutic failure (3/4 versus 4/7) or uncleared fungemia (4/6 versus 4/10), but FNS isolates were identified more frequently from patients with previous azole exposure (6/6 versus 3/10;P= 0.011) and immunosuppression (6/6 versus 3/10;P= 0.011). These results reveal that the majority of FNSC. tropicalisisolates show overexpression ofCDR1,MDR1, andERG11genes, and fungemia develops after azole exposure in patients with immunosuppression.

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Diverse Energy-Conserving Pathways in Clostridium difficile: Growth in the Absence of Amino Acid Stickland Acceptors and the Role of the Wood-Ljungdahl Pathway

Journal of Bacteriology ◽

10.1128/jb.00233-20 ◽

2020 ◽

Vol 202 (20) ◽

Cited By ~ 1

Author(s):

Simonida Gencic ◽

David A. Grahame

Keyword(s):

Amino Acid ◽

Clostridium Difficile ◽

Central Component ◽

Content Increase ◽

Efficient System ◽

Content Type ◽

Atp Production ◽

Cell Extracts ◽

Complete Set

ABSTRACT Clostridium difficile is the leading cause of hospital-acquired antibiotic-associated diarrhea and is the only widespread human pathogen that contains a complete set of genes encoding the Wood-Ljungdahl pathway (WLP). In acetogenic bacteria, synthesis of acetate from 2 CO2 molecules by the WLP functions as a terminal electron accepting pathway; however, C. difficile contains various other reductive pathways, including a heavy reliance on Stickland reactions, which questions the role of the WLP in this bacterium. In rich medium containing high levels of electron acceptor substrates, only trace levels of key WLP enzymes were found; therefore, conditions were developed to adapt C. difficile to grow in the absence of amino acid Stickland acceptors. Growth conditions were identified that produce the highest levels of WLP activity, determined by Western blot analyses of the central component acetyl coenzyme A synthase (AcsB) and assays of other WLP enzymes. Fermentation substrate and product analyses, enzyme assays of cell extracts, and characterization of a ΔacsB mutant demonstrated that the WLP functions to dispose of metabolically generated reducing equivalents. While WLP activity in C. difficile does not reach the levels seen in classical acetogens, coupling of the WLP to butyrate formation provides a highly efficient system for regeneration of NAD+ “acetobutyrogenesis,” requiring only low flux through the pathways to support efficient ATP production from glucose oxidation. Additional insights redefine the amino acid requirements in C. difficile, explore the relationship of the WLP to toxin production, and provide a rationale for colocalization of genes involved in glycine synthesis and cleavage within the WLP operon. IMPORTANCE Clostridium difficile is an anaerobic, multidrug-resistant, toxin-producing pathogen with major health impacts worldwide. It is the only widespread pathogen harboring a complete set of Wood-Ljungdahl pathway (WLP) genes; however, the role of the WLP in C. difficile is poorly understood. In other anaerobic bacteria and archaea, the WLP can operate in one direction to convert CO2 to acetic acid for biosynthesis or in either direction for energy conservation. Here, conditions are defined in which WLP levels in C. difficile increase markedly, functioning to support metabolism of carbohydrates. Amino acid nutritional requirements were better defined, with new insight into how the WLP and butyrate pathways act in concert, contributing significantly to energy metabolism by a mechanism that may have broad physiological significance within the group of nonclassical acetogens.

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A Novel, WidespreadqacAAllele Results in Reduced Chlorhexidine Susceptibility inStaphylococcus epidermidis

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02607-18 ◽

2019 ◽

Vol 63 (6) ◽

Cited By ~ 3

Author(s):

Amin Addetia ◽

Alexander L. Greninger ◽

Amanda Adler ◽

Shuhua Yuan ◽

Negar Makhsous ◽

...

Keyword(s):

Amino Acid ◽

Staphylococcus Epidermidis ◽

Sequence Data ◽

Methicillin Resistance ◽

Single Amino Acid ◽

Data Sets ◽

The Novel ◽

Content Type

ABSTRACTChlorhexidine gluconate (CHG) is a topical antiseptic widely used in health care settings. InStaphylococcusspp., the pump QacA effluxes CHG, while the closely related QacB cannot due to a single amino acid substitution. We characterized 1,050 cutaneousStaphylococcusisolates obtained from 173 pediatric oncology patients enrolled in a multicenter CHG bathing trial. CHG susceptibility testing revealed that 63 (6%) of these isolates had elevated CHG MICs (≥4 μg/ml). Screening of all 1,050 isolates for theqacA/Bgene (the sameqacgene with A or B allele) by restriction fragment length polymorphism (RFLP) yielded 56 isolates with a novelqacA/BRFLP pattern,qacA/B273. The CHG MIC was significantly higher forqacA/B273-positive isolates (MIC50, 4 μg/ml; MIC range, 0.5 to 4 μg/ml) than for otherqacgroups:qacA-positive isolates (n = 559; MIC50, 1 μg/ml; MIC range, 0.5 to 4 μg/ml),qacB-positive isolates (n = 17; MIC50, 1 μg/ml; MIC range, 0.25 to 2 μg/ml), andqacA/B-negative isolates (n = 418, MIC50, 1 μg/ml; MIC range, 0.125 to 2 μg/ml) (P = 0.001). A high proportion of theqacA/B273-positive isolates also displayed methicillin resistance (96.4%) compared to the otherqacgroups (24.9 to 61.7%) (P = 0.001). Whole-genome sequencing revealed thatqacA/B273-positive isolates encoded a variant of QacA with 2 amino acid substitutions. This new allele, namedqacA4, was carried on the novel plasmid pAQZ1. TheqacA4-carrying isolates belonged to the highly resistantStaphylococcus epidermidissequence type 2 clone. By searching available sequence data sets, we identified 39 additionalqacA4-carryingS. epidermidisstrains from 5 countries. Curing an isolate ofqacA4resulted in a 4-fold decrease in the CHG MIC, confirming the role ofqacA4in the elevated CHG MIC. Our results highlight the importance of further studyingqacA4and its functional role in clinical staphylococci.

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Factors affecting excitatory amino acid release following severe human head injury

Journal of Neurosurgery ◽

10.3171/jns.1998.89.4.0507 ◽

1998 ◽

Vol 89 (4) ◽

pp. 507-518 ◽

Cited By ~ 365

Author(s):

Ross Bullock ◽

Alois Zauner ◽

John J. Woodward ◽

John Myseros ◽

Sung C. Choi ◽

...

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Brain Injury ◽

Head Injury ◽

Neuronal Damage ◽

Cell Swelling ◽

Glutamate Antagonists ◽

Content Type ◽

Fine Print

Object. Recent animal studies demonstrate that excitatory amino acids (EAAs) play a major role in neuronal damage after brain trauma and ischemia. However, the role of EAAs in patients who have suffered severe head injury is not understood. Excess quantities of glutamate in the extracellular space may lead to uncontrolled shifts of sodium, potassium, and calcium, disrupting ionic homeostasis, which may lead to severe cell swelling and cell death. The authors evaluated the role of EEAs in human traumatic brain injury. Methods. In 80 consecutive severely head injured patients, a microdialysis probe was placed into the gray matter along with a ventriculostomy catheter or an intracranial pressure (ICP) monitor for 4 days. Levels of EAAs and structural amino acids were analyzed using high-performance liquid chromatography. Multifactorial analysis of the amino acid pattern was performed and its correlations with clinical parameters and outcome were tested. The levels of EAAs were increased up to 50 times normal in 30% of the patients and were significantly correlated to levels of structural amino acids both in each patient and across the whole group (p < 0.01). Secondary ischemic brain injury and focal contusions were most strongly associated with high EAA levels (27 ± 22 µmol/L). Sustained high ICP and poor outcome were significantly correlated to high levels of EAAs (glutamate > 20 µmol/L; p < 0.01). Conclusions. The release of EAAs is closely linked to the release of structural amino acids and may thus reflect nonspecific development of membrane micropores, rather than presynaptic neuronal vesicular exocytosis. The magnitude of EAA release in patients with focal contusions and ischemic events may be sufficient to exacerbate neuronal damage, and these patients may be the best candidates for treatment with glutamate antagonists in the future.

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Exploring the Role of the Ω-Loop in the Evolution of Ceftazidime Resistance in the PenA β-Lactamase from Burkholderia multivorans, an Important Cystic Fibrosis Pathogen

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01941-16 ◽

2016 ◽

Vol 61 (2) ◽

Cited By ~ 5

Author(s):

Krisztina M. Papp-Wallace ◽

Scott A. Becka ◽

Magdalena A. Taracila ◽

Elise T. Zeiser ◽

Julian A. Gatta ◽

...

Keyword(s):

Amino Acid ◽

Burkholderia Cepacia ◽

Clinical Isolates ◽

Dynamics Simulation ◽

Single Amino Acid ◽

Amino Acid Substitutions ◽

Biochemical Basis ◽

Content Type ◽

Burkholderia Multivorans

ABSTRACT The unwelcome evolution of resistance to the advanced generation cephalosporin antibiotic, ceftazidime is hindering the effective therapy of Burkholderia cepacia complex (BCC) infections. Regrettably, BCC organisms are highly resistant to most antibiotics, including polymyxins; ceftazidime and trimethoprim-sulfamethoxazole are the most effective treatment options. Unfortunately, resistance to ceftazidime is increasing and posing a health threat to populations susceptible to BCC infection. We found that up to 36% of 146 tested BCC clinical isolates were nonsusceptible to ceftazidime (MICs ≥ 8 μg/ml). To date, the biochemical basis for ceftazidime resistance in BCC is largely undefined. In this study, we investigated the role of the Ω-loop in mediating ceftazidime resistance in the PenA β-lactamase from Burkholderia multivorans, a species within the BCC. Single amino acid substitutions were engineered at selected positions (R164, T167, L169, and D179) in the PenA β-lactamase. Cell-based susceptibility testing revealed that 21 of 75 PenA variants engineered in this study were resistant to ceftazidime, with MICs of >8 μg/ml. Under steady-state conditions, each of the selected variants (R164S, T167G, L169A, and D179N) demonstrated a substrate preference for ceftazidime compared to wild-type PenA (32- to 320-fold difference). Notably, the L169A variant hydrolyzed ceftazidime significantly faster than PenA and possessed an ∼65-fold-lower apparent Ki (Ki app) than that of PenA. To understand why these amino acid substitutions result in enhanced ceftazidime binding and/or turnover, we employed molecular dynamics simulation (MDS). The MDS suggested that the L169A variant starts with the most energetically favorable conformation (−28.1 kcal/mol), whereas PenA possessed the most unfavorable initial conformation (136.07 kcal/mol). In addition, we observed that the spatial arrangement of E166, N170, and the hydrolytic water molecules may be critical for enhanced ceftazidime hydrolysis by the L169A variant. Importantly, we found that two clinical isolates of B. multivorans possessed L169 amino acid substitutions (L169F and L169P) in PenA and were highly resistant to ceftazidime (MICs ≥ 512 μg/ml). In conclusion, substitutions in the Ω-loop alter the positioning of the hydrolytic machinery as well as allow for a larger opening of the active site to accommodate the bulky R1 and R2 side chains of ceftazidime, resulting in resistance. This analysis provides insights into the emerging phenotype of ceftazidime-resistant BCC and explains the evolution of amino acid substitutions in the Ω-loop of PenA of this significant clinical pathogen.

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Reassessment of the Role of Aromatic Amino Acid Hydroxylases and the Effect of Infection by Toxoplasma gondii on Host Dopamine

Infection and Immunity ◽

10.1128/iai.02465-14 ◽

2014 ◽

Vol 83 (3) ◽

pp. 1039-1047 ◽

Cited By ~ 46

Author(s):

Zi T. Wang ◽

Steve Harmon ◽

Karen L. O'Malley ◽

L. David Sibley

Keyword(s):

Amino Acid ◽

Toxoplasma Gondii ◽

Aromatic Amino Acid ◽

Content Type ◽

Aromatic Amino Acid Hydroxylase ◽

Aromatic Amino Acid Hydroxylases ◽

Host Brain

Toxoplasma gondiiinfection has been described previously to cause infected mice to lose their fear of cat urine. This behavioral manipulation has been proposed to involve alterations of host dopamine pathways due to parasite-encoded aromatic amino acid hydroxylases. Here, we report successful knockout and complementation of the aromatic amino acid hydroxylaseAAH2gene, with no observable phenotype in parasite growth or differentiationin vitroandin vivo. Additionally, expression levels of the two aromatic amino acid hydroxylases were negligible both in tachyzoites and in bradyzoites. Finally, we were unable to confirm previously described effects of parasite infection on host dopamine eitherin vitroorin vivo, even whenAAH2was overexpressed using theBAG1promoter. Together, these data indicate that AAH enzymes in the parasite do not cause global or regional alterations of dopamine in the host brain, although they may affect this pathway locally. Additionally, our findings suggest alternative roles for theAHHenzymes inT. gondii, sinceAAH1is essential for growth in nondopaminergic cells.

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