RESUMO
In this study, we compared the effects of endurance training in the fasted state (F) vs. the fed state [ample carbohydrate intake (CHO)] on exercise-induced intramyocellular lipid (IMCL) and glycogen utilization during a 6-wk period of a hypercaloric (â¼+30% kcal/day) fat-rich diet (HFD; 50% of kcal). Healthy male volunteers (18-25 yrs) received a HFD in conjunction with endurance training (four times, 60-90 min/wk) either in F (n = 10) or with CHO before and during exercise sessions (n = 10). The control group (n = 7) received a HFD without training and increased body weight by â¼3 kg (P < 0.001). Before and after a HFD, the subjects performed a 2-h constant-load bicycle exercise test in F at â¼70% maximal oxygen uptake rate. A HFD, both in the absence (F) or presence (CHO) of training, elevated basal IMCL content by â¼50% in type I and by â¼75% in type IIa fibers (P < 0.05). Independent of training in F or CHO, a HFD, as such, stimulated exercise-induced net IMCL breakdown by approximately twofold in type I and by approximately fourfold in type IIa fibers. Furthermore, exercise-induced net muscle glycogen breakdown was not significantly affected by a HFD. It is concluded that a HFD stimulates net IMCL degradation by increasing basal IMCL content during exercise in type I and especially IIa fibers. Furthermore, a hypercaloric HFD provides adequate amounts of carbohydrates to maintain high muscle glycogen content during training and does not impair exercise-induced muscle glycogen breakdown.
Assuntos
Gorduras na Dieta/metabolismo , Ingestão de Energia , Metabolismo Energético , Exercício Físico , Metabolismo dos Lipídeos , Fibras Musculares Esqueléticas/metabolismo , Resistência Física , Proteínas Quinases Ativadas por AMP/metabolismo , Acetil-CoA Carboxilase/metabolismo , Adolescente , Adulto , Análise de Variância , Bélgica , Carboidratos da Dieta/administração & dosagem , Carboidratos da Dieta/metabolismo , Gorduras na Dieta/administração & dosagem , Teste de Esforço , Jejum/metabolismo , Ácidos Graxos não Esterificados/sangue , Regulação Enzimológica da Expressão Gênica , Glicogênio/metabolismo , Humanos , Masculino , Consumo de Oxigênio , Fosforilação , Proteínas Serina-Treonina Quinases/genética , Piruvato Desidrogenase Quinase de Transferência de Acetil , RNA Mensageiro/metabolismo , Fatores de Tempo , Aumento de Peso , Adulto JovemRESUMO
The effect of creatine supplementation, alone or in combination with exercise training, on insulin sensitivity, intramyocellular lipid content (IMCL) and fatty acid translocase (FAT)/CD36 content was investigated in rats fed a sucrose-rich cafeteria diet during 12 weeks. Five experimental conditions were CON, receiving normal pellets; CAF, fed the cafeteria diet; CAF(TR), fed the cafeteria diet together with exercise training in weeks 8-12 and CAF(CR) and CAF(CRT) that were analogous to CAF and CAF(TR), respectively, but which received daily 2.5% of creatine monohydrate. During intravenous glucose tolerance test, compared with CON, whole-body glucose tolerance was reduced in CAF and CAF(CR) but not in CAF(TR) and CAF(CRT). Insulin-stimulated glucose transport in perfused red gastrocnemius muscles was impaired in CAF and CAF(CR) but not in the trained groups. IMCL content in soleus and extensor digitorum longus muscles was higher in CAF than in CON, but not in CAF(TR), CAF(CR) and CAF(CRT). Compared with CON and CAF, FAT/CD36 protein content in m. soleus, was ~40% lower in CAF(CR), CAF(TR) and CAF(CRT). The fraction of fecal fat, as determined in a 3-week post hoc study, was 25% higher in CAF(CR) than in CON. Moreover, in CAF(CR), triglyceride concentration in blood and liver were significantly lower than in CAF. It is concluded that creatine supplementation in rats on a cafeteria diet inhibits IMCL accumulation via inhibition of gastrointestinal lipid absorption together with lower muscle FAT/CD36 content. Furthermore, exercise-induced but not creatine-induced reduction of IMCL is associated with improved insulin action on glucose transport in muscle cells.
Assuntos
Creatina/metabolismo , Resistência à Insulina , Insulina/metabolismo , Condicionamento Físico Animal , Animais , Glicemia/metabolismo , Gorduras na Dieta/farmacologia , Metabolismo dos Lipídeos , Masculino , Músculo Esquelético/metabolismo , Ratos , Ratos WistarRESUMO
Training with limited carbohydrate availability can stimulate adaptations in muscle cells to facilitate energy production via fat oxidation. Here we investigated the effect of consistent training in the fasted state, vs. training in the fed state, on muscle metabolism and substrate selection during fasted exercise. Twenty young male volunteers participated in a 6-wk endurance training program (1-1.5 h cycling at â¼70% Vo(2max), 4 days/wk) while receiving isocaloric carbohydrate-rich diets. Half of the subjects trained in the fasted state (F; n = 10), while the others ingested ample carbohydrates before (â¼160 g) and during (1 g·kg body wt⻹·h⻹) the training sessions (CHO; n = 10). The training similarly increased Vo(2max) (+9%) and performance in a 60-min simulated time trial (+8%) in both groups (P < 0.01). Metabolic measurements were made during a 2-h constant-load exercise bout in the fasted state at â¼65% pretraining Vo(2max). In F, exercise-induced intramyocellular lipid (IMCL) breakdown was enhanced in type I fibers (P < 0.05) and tended to be increased in type IIa fibers (P = 0.07). Training did not affect IMCL breakdown in CHO. In addition, F (+21%) increased the exercise intensity corresponding to the maximal rate of fat oxidation more than did CHO (+6%) (P < 0.05). Furthermore, maximal citrate synthase (+47%) and ß-hydroxyacyl coenzyme A dehydrogenase (+34%) activity was significantly upregulated in F (P < 0.05) but not in CHO. Also, only F prevented the development exercise-induced drop in blood glucose concentration (P < 0.05). In conclusion, F is more effective than CHO to increase muscular oxidative capacity and at the same time enhances exercise-induced net IMCL degradation. In addition, F but not CHO prevented drop of blood glucose concentration during fasting exercise.
Assuntos
Adaptação Fisiológica/fisiologia , Glicemia/metabolismo , Exercício Físico/fisiologia , Jejum/fisiologia , Consumo de Oxigênio/fisiologia , Resistência Física/fisiologia , Aptidão Física/fisiologia , Humanos , Masculino , Adulto JovemRESUMO
A fat-rich energy-dense diet is an important cause of insulin resistance. Stimulation of fat turnover in muscle cells during dietary fat challenge may contribute to maintenance of insulin sensitivity. Exercise in the fasted state markedly stimulates energy provision via fat oxidation. Therefore, we investigated whether exercise training in the fasted state is more potent than exercise in the fed state to rescue whole-body glucose tolerance and insulin sensitivity during a period of hyper-caloric fat-rich diet. Healthy male volunteers (18-25 y) received a hyper-caloric (â¼+30% kcal day(-1)) fat-rich (50% of kcal) diet for 6 weeks. Some of the subjects performed endurance exercise training (4 days per week) in the fasted state (F; n = 10), whilst the others ingested carbohydrates before and during the training sessions (CHO; n = 10). The control group did not train (CON; n = 7). Body weight increased in CON (+3.0 ± 0.8 kg) and CHO (+1.4 ± 0.4 kg) (P < 0.01), but not in F (+0.7 ± 0.4 kg, P = 0.13). Compared with CON, F but not CHO enhanced whole-body glucose tolerance and the Matsuda insulin sensitivity index (P < 0.05). Muscle GLUT4 protein content was increased in F (+28%) compared with both CHO (P = 0.05) and CON (P < 0.05). Furthermore, only training in F elevated AMP-activated protein kinase α phosphorylation (+25%) as well as up-regulated fatty acid translocase/CD36 and carnitine palmitoyltransferase 1 mRNA levels compared with CON (â¼+30%). High-fat diet increased intramyocellular lipid but not diacylglycerol and ceramide contents, either in the absence or presence of training. This study for the first time shows that fasted training is more potent than fed training to facilitate adaptations in muscle and to improve whole-body glucose tolerance and insulin sensitivity during hyper-caloric fat-rich diet.
Assuntos
Gorduras na Dieta/metabolismo , Exercício Físico/fisiologia , Jejum/fisiologia , Glucose/metabolismo , Resistência à Insulina/fisiologia , Composição Corporal/fisiologia , Ácidos Graxos não Esterificados/sangue , Glicogênio/metabolismo , Humanos , Metabolismo dos Lipídeos/fisiologia , Masculino , Músculo Esquelético/metabolismo , Resistência Física/fisiologia , Adulto JovemRESUMO
Intramyocellular lipids (IMCL) and mitochondrial uncoupling protein-3 (UCP3) have been implicated in the development of muscular insulin resistance. This study aimed to investigate the role of IMCL and UCP3 in the development of glucose intolerance and muscular insulin resistance during 12 weeks of an obesity-inducing 'cafeteria-style' diet alone (CAF), or in conjunction with exercise training from weeks 8-12 (CAFTR), in rats. At the end of the intervention period, gain in body weight was 20% higher in CAF (305+/-10 g) than controls (CON) (255+/-14 g; p<0.001) and CAFTR (253+/-7 g; p<0.001). Furthermore, compared with CON, the Matsuda insulin sensitivity index (ISI), assessed during a 2-h intravenous glucose tolerance test, was markedly lower in CAF (6.7+/-0.4) than in either CON (15.6+/-1.4; p<0.001) or CAFTR (11.2+/-1.1; p<0.001). Moreover, in CAF glucose transport at a submaximal insulin concentration (200 microU/ml) was reduced by approximately 60% (p<0.05) in both red and white gastrocnemius muscles, but not in m. soleus. However, glucose transport in CAFTR was similar to CON in red gastrocnemius. In CAF fiber-specific IMCL content determined in m. soleus and extensor digitorum longus (EDL), was higher than in CON (p<0.01) and CAFTR (p<0.001). Muscle UCP3 protein content was not changed by any of the interventions. Interestingly, within CAF and CAFTR, ISI closely negatively correlated with IMCL content in both type I (soleus, r=-0.93; EDL, r=-0.90; p<0.05) and IIa (EDL, r=-0.52, p<0.05) muscle fibers. These findings indicate that changes in IMCL content but not UCP3 content are implicated in short-term effects of cafeteria-style diet and exercise training on muscular insulin sensitivity in rats.
Assuntos
Dieta , Hiperglicemia/metabolismo , Insulina/farmacologia , Canais Iônicos/metabolismo , Metabolismo dos Lipídeos/efeitos dos fármacos , Proteínas Mitocondriais/metabolismo , Músculo Esquelético/metabolismo , Condicionamento Físico Animal , Animais , Glicemia/efeitos dos fármacos , Glicemia/metabolismo , Peso Corporal/efeitos dos fármacos , Ácidos Graxos/metabolismo , Comportamento Alimentar/efeitos dos fármacos , Regulação da Expressão Gênica/efeitos dos fármacos , Intolerância à Glucose/complicações , Intolerância à Glucose/metabolismo , Hiperglicemia/complicações , Insulina/sangue , Resistência à Insulina , Canais Iônicos/genética , Masculino , Proteínas Mitocondriais/genética , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/patologia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Proteína Desacopladora 3RESUMO
The N-terminal 1-225 amino acids (aa) of the type 1 inositol 1,4,5-trisphosphate receptor (IP(3)R1) function as a suppressor/coupling domain. In this study we used IP(3)R-deficient B-lymphocytes to investigate the effects of modifications in this domain on IP(3) binding and Ca(2+)-release activity. Although the N-terminal 1-225 aa of IP(3)R3 had the same role as in IP(3)R1, the suppression of IP(3) binding for IP(3)R1 was lost when the suppressor/coupling domains were exchanged between the two isoforms. Resulting chimeric receptors showed a higher sensitivity to IP(3)-induced activation (IICR). Deletion of 11 aa in IP(3)R1 ([Delta76-86]-IP(3)R1) or replacing aa 76-86 of the IP(3)R1 in the suppressor/coupling domain by 13 aa of IP(3)R3 ([75-87 T3]-IP(3)R1) also resulted in increased IP(3) binding and sensitivity of IICR. These residues constitute the only part of the suppressor/coupling domain that is strikingly different between the two isoforms. Expression of [Delta76-86]-IP(3)R1 and of [75-87 T3]-IP(3)R1 increased the propensity of cells to undergo staurosporine-induced apoptosis, but had no effect on the Ca(2+) content in the endoplasmic reticulum. In the cell model used, our observations suggest that the sensitivity of the Ca(2+)-release activity of IP(3)R1 to IP(3) influences the sensitivity of the cells to apoptotic stimuli and that the suppressor/coupling domain may have an anti-apoptotic function by attenuating the sensitivity of IICR.
Assuntos
Apoptose/fisiologia , Canais de Cálcio/fisiologia , Cálcio/fisiologia , Inositol 1,4,5-Trifosfato/metabolismo , Receptores Citoplasmáticos e Nucleares/fisiologia , Sequência de Aminoácidos , Animais , Sítios de Ligação/fisiologia , Cálcio/metabolismo , Canais de Cálcio/genética , Caspase 3 , Caspases/metabolismo , Linhagem Celular , Galinhas , Sequência Conservada , Genes Supressores/fisiologia , Humanos , Receptores de Inositol 1,4,5-Trifosfato , Dados de Sequência Molecular , Estrutura Terciária de Proteína/fisiologia , Receptores Citoplasmáticos e Nucleares/genética , Homologia de Sequência de AminoácidosRESUMO
Ca(2+) release via intracellular release channels, IP(3)Rs (inositol 1,4,5-trisphosphate receptors) and RyRs (ryanodine receptors), is perhaps the most ubiquitous and versatile cellular signalling mechanism, and is involved in a vast number of cellular processes. In addition to this classical release pathway there is limited, but yet persistent, information about less well-defined Ca(2+)-leak pathways that may play an important role in the control of the Ca(2+) load of the endo(sarco)plasmic reticulum. The mechanisms responsible for this 'basal' leak are not known, but recent data suggest that both IP(3)Rs and RyRs may also operate as Ca(2+)-leak channels, particularly in pathological conditions. Proteolytic cleavage or biochemical modification (such as hyperphosphorylation or nitrosylation), for example, occurring during conditions of cell stress or apoptosis, can functionally uncouple the cytoplasmic control domains from the channel domain of the receptor. Highly significant information has been obtained from studies of malfunctioning channels in various disorders; for example, RyRs in cardiac malfunction or genetic muscle diseases and IP(3)Rs in neurodegenerative diseases. In this review we aim to summarize the existing information about functionally uncoupled IP(3)R and RyR channels, and to discuss the concept that those channels can participate in Ca(2+)-leak pathways.
Assuntos
Canais de Cálcio/química , Canais de Cálcio/fisiologia , Sinalização do Cálcio/fisiologia , Receptores Citoplasmáticos e Nucleares/química , Receptores Citoplasmáticos e Nucleares/fisiologia , Animais , Receptores de Inositol 1,4,5-Trifosfato , Modelos Biológicos , Fosforilação/efeitos dos fármacos , Mapeamento de Interação de Proteínas , Canal de Liberação de Cálcio do Receptor de Rianodina/fisiologiaRESUMO
Calmodulin (CaM) is a ubiquitous Ca(2+)-sensor protein that plays an important role in regulating a large number of Ca(2+) channels, including the inositol 1,4,5-trisphosphate receptor (IP(3)R). CaM binds to the IP(3)R at Ca(2+)-dependent as well as at Ca(2+)-independent interaction sites. In this study, we have investigated the Ca(2+)-independent CaM-binding site for its role in the regulation of the Ca(2+)-dependent bell-shaped activation curve of the IP(3)R. Suramin, a polysulfonated napthylurea, displaced CaM in both the presence and the absence of Ca(2+). Suramin competed with CaM for binding to different peptides representing the previously identified CaM-binding sites on IP(3)R1. By interacting with the N-terminal Ca(2+)-independent CaM-binding site, suramin mimicked the functional effect of CaM and induced an allosteric but competitive inhibition of IP(3) binding. Therefore, suramin also potently inhibited IP(3)-induced Ca(2+) release (IICR) from permeabilized cells predominantly expressing IP(3)R1 (L15 fibroblasts) or IP(3)R3 (Lvec fibroblasts), even though the IP(3)R3 does not contain Ca(2+)-dependent CaM-binding sites. Furthermore, we have found that CaM(1234), a CaM mutated in its four EF hands, inhibited IICR in a Ca(2+)-dependent way with the same potency as CaM. We conclude that CaM inhibits IICR via the N-terminal binding site. The inhibition requires Ca(2+) but CaM itself is not the Ca(2+) sensor for the inhibition of the IP(3)R.
Assuntos
Canais de Cálcio/metabolismo , Cálcio/metabolismo , Calmodulina/antagonistas & inibidores , Inositol 1,4,5-Trifosfato/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Animais , Sítios de Ligação , Calmodulina/metabolismo , Células Cultivadas , Receptores de Inositol 1,4,5-Trifosfato , Insetos , Estrutura Terciária de Proteína , Suramina/metabolismoRESUMO
Inositol 1,4,5-trisphosphate receptor-deficient (IP3RKO) B-lymphocytes were used to investigate the functional relevance of type 1 inositol 1,4,5-trisphosphate receptor (IP3R1) and its cleavage by caspase-3 in apoptosis. We showed that inositol 1,4,5-trisphosphate receptor-deficient cells were largely resistant to apoptosis induced by both staurosporine (STS) and B-cell receptor (BCR) stimulation. Expression of either the wild-type IP3R1 or an N-terminal deletion mutant (Delta1-225) that lacks inositol 1,4,5-trisphosphate-induced Ca2+ release activity restored sensitivity to apoptosis and the consequent rise in free cytosolic Ca2+ concentration ([Ca2+]i). Expression of caspase-3-non-cleavable mutant receptor, however, dramatically slowed down the rate of apoptosis and prevented both Ca2+ overload and secondary necrosis. Conversely, expression of the "channel-only" domain of IP3R1, a fragment of the receptor generated by caspase-3 cleavage, strongly increased the propensity of the cells to undergo apoptosis. In agreement with these observations, caspase inhibitors impeded apoptosis and the associated rise in [Ca2+]i. Both the staurosporine- and B-cell receptor-induced apoptosis and increase in [Ca2+]i could be induced in nominally Ca2+-free and serum-free culture media, suggesting that the apoptosis-related rise in [Ca2+]i was primarily because of the release from internal stores rather than of influx through the plasma membrane. Altogether, our results suggest that IP3R1 plays a pivotal role in apoptosis and that the increase in [Ca2+]i during apoptosis is mainly the consequence of IP3R1 cleavage by caspase-3. These observations also indicate that expression of a functional IP3R1 per se is not enough to generate the significant levels of cytosolic Ca2+ needed for the rapid execution of apoptosis, but a prior activation of caspase-3 and the resulting truncation of the IP3R1 are required.
Assuntos
Canais de Cálcio/química , Cálcio/metabolismo , Caspases/metabolismo , Inositol 1,4,5-Trifosfato/química , Receptores Citoplasmáticos e Nucleares/química , Animais , Apoptose , Linfócitos B/metabolismo , Caspase 3 , Morte Celular , Membrana Celular/metabolismo , Cerebelo/metabolismo , Galinhas , Meios de Cultura Livres de Soro/metabolismo , Citosol/metabolismo , DNA/metabolismo , Inibidores Enzimáticos/farmacologia , Citometria de Fluxo , Deleção de Genes , Receptores de Inositol 1,4,5-Trifosfato , Camundongos , Microssomos/metabolismo , Mutação , Necrose , Estrutura Terciária de Proteína , Receptores de Antígenos de Linfócitos B/metabolismo , Proteínas Recombinantes/química , Estaurosporina/farmacologia , Fatores de Tempo , TransfecçãoRESUMO
Thiol-reactive agents such as thimerosal have been shown to modulate the Ca2+-flux properties of IP3 (inositol 1,4,5-trisphosphate) receptor (IP3R) via an as yet unidentified mechanism [Parys, Missiaen, De Smedt, Droogmans and Casteels (1993) Pflügers Arch. 424, 516-522; Kaplin, Ferris, Voglmaier and Snyder (1994) J. Biol. Chem. 269, 28972-28978; Missiaen, Taylor and Berridge (1992) J. Physiol. (Cambridge, U.K.) 455, 623-640; Missiaen, Parys, Sienaert, Maes, Kunzelmann, Takahashi, Tanzawa and De Smedt (1998) J. Biol. Chem. 273, 8983-8986]. In the present study, we show that thimerosal potentiated IICR (IP3-induced Ca2+ release) and IP3-binding activity of IP3R1, expressed in triple IP3R-knockout R23-11 cells derived from DT40 chicken B lymphoma cells, but not of IP3R3 or [D1-225]-IP3R1, which lacks the N-terminal suppressor domain. Using a 45Ca2+-flux technique in permeabilized A7r5 smooth-muscle cells, we have shown that Ca2+ shifted the stimulatory effect of thimerosal on IICR to lower concentrations of thimerosal and thereby increased the extent of Ca2+ release. This suggests that Ca2+ and thimerosal synergetically regulate IP3R1. Glutathione S-transferase pull-down experiments elucidated an interaction between amino acids 1-225 (suppressor domain) and amino acids 226-604 (IP3-binding core) of IP3R1, and this interaction was strengthened by both Ca2+ and thimerosal. In contrast, calmodulin and sCaBP-1 (short Ca2+-binding protein-1), both having binding sites in the 1-225 region, weakened the interaction. This interaction was not found for IP3R3, in agreement with the lack of functional stimulation of this isoform by thimerosal. The interaction between the IP3-binding and transmembrane domains (amino acids 1-604 and 2170-2749 respectively) was not affected by thimerosal and Ca2+, but it was significantly inhibited by IP3 and adenophostin A. Our results demonstrate that thimerosal and Ca2+ induce isoform-specific conformational changes in the N-terminal part of IP3R1, leading to the formation of a highly IP3-sensitive Ca2+-release channel.
Assuntos
Canais de Cálcio/metabolismo , Cálcio/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Timerosal/farmacologia , Animais , Aorta/química , Aorta/efeitos dos fármacos , Aorta/embriologia , Aorta/metabolismo , Células COS , Canais de Cálcio/biossíntese , Canais de Cálcio/química , Canais de Cálcio/deficiência , Sinalização do Cálcio/efeitos dos fármacos , Linhagem Celular , Linhagem Celular Tumoral , Permeabilidade da Membrana Celular/efeitos dos fármacos , Galinhas , Chlorocebus aethiops , Glutationa Transferase/biossíntese , Glutationa Transferase/química , Receptores de Inositol 1,4,5-Trifosfato , Músculo Liso Vascular/citologia , Músculo Liso Vascular/efeitos dos fármacos , Músculo Liso Vascular/metabolismo , Peptídeos/metabolismo , Ligação Proteica/efeitos dos fármacos , Conformação Proteica/efeitos dos fármacos , Isoformas de Proteínas/metabolismo , Estrutura Terciária de Proteína , Ratos , Receptores Citoplasmáticos e Nucleares/biossíntese , Receptores Citoplasmáticos e Nucleares/química , Receptores Citoplasmáticos e Nucleares/deficiência , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Deleção de Sequência/genética , Deleção de Sequência/fisiologia , Compostos de Sulfidrila/farmacologia , Timerosal/metabolismoRESUMO
Deletion of trehalose-6-phosphate phosphatase, encoded by TPS2, in Saccharomyces cerevisiae results in accumulation of trehalose-6-phosphate (Tre6P) instead of trehalose under stress conditions. Since trehalose is an important stress protectant and Tre6P accumulation is toxic, we have investigated whether Tre6P phosphatase could be a useful target for antifungals in Candida albicans. We have cloned the C. albicans TPS2 (CaTPS2) gene and constructed heterozygous and homozygous deletion strains. As in S. cerevisiae, complete inactivation of Tre6P phosphatase in C. albicans results in 50-fold hyperaccumulation of Tre6P, thermosensitivity, and rapid death of the cells after a few hours at 44 degrees C. As opposed to inactivation of Tre6P synthase by deletion of CaTPS1, deletion of CaTPS2 does not affect hypha formation on a solid glucose-containing medium. In spite of this, virulence of the homozygous deletion mutant is strongly reduced in a mouse model of systemic infection. The pathogenicity of the heterozygous deletion mutant is similar to that of the wild-type strain. CaTPS2 is a new example of a gene not required for growth under standard conditions but required for pathogenicity in a host. Our results suggest that Tre6P phosphatase may serve as a potential target for antifungal drugs. Neither Tre6P phosphatase nor its substrate is present in mammals, and assay of the enzymes is simple and easily automated for high-throughput screening.