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1.
Open Forum Infect Dis ; 10(4): ofad155, 2023 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-37035495

RESUMEN

Background: Coronavirus disease 2019 (COVID-19)-associated pulmonary aspergillosis (CAPA) is likely underdiagnosed, and current diagnostic tools are either invasive or insensitive. Methods: A retrospective study of mechanically ventilated patients with COVID-19 admitted to 5 Johns Hopkins hospitals between March 2020 and June 2021 was performed. Multivariable logistic regression was used for the CAPA prediction model building. Performance of the model was assessed using the area under the receiver operating characteristic curve (AUC). Results: In the cohort of 832 patients, 98 (11.8%) met criteria for CAPA. Age, time since intubation, dexamethasone for COVID-19 treatment, underlying pulmonary circulatory diseases, human immunodeficiency virus, multiple myeloma, cancer, or hematologic malignancies were statistically significantly associated with CAPA and were included in the CAPA prediction model, which showed an AUC of 0.75 (95% confidence interval, .70-.80). At a screening cutoff of ≥0.085, it had a sensitivity of 82%, a specificity of 51%, a positive predictive value of 18.6%, and a negative predictive value of 95.3%. (The CAPA screening score calculator is available at www.transplantmodels.com). Conclusions: We developed a CAPA risk score as a noninvasive tool to aid in CAPA screening for patients with severe COVID-19. Our score will also identify a group of patients who are unlikely to have CAPA and who therefore need not undergo additional diagnostics and/or empiric antifungal therapy.

2.
Clin Infect Dis ; 74(1): 83-91, 2022 01 07.
Artículo en Inglés | MEDLINE | ID: mdl-33693551

RESUMEN

BACKGROUND: Coronavirus disease 2019 (COVID-19)-associated pulmonary aspergillosis (CAPA) occurs in critically ill patients with COVID-19. Risks and outcomes remain poorly understood. METHODS: A retrospective cohort study of mechanically ventilated adult patients with COVID-19 admitted to 5 Johns Hopkins hospitals was conducted between March and August 2020. CAPA was defined using composite clinical criteria. Fine and Gray competing risks regression was used to analyze clinical outcomes and, multilevel mixed-effects ordinal logistic regression was used to compare longitudinal disease severity scores. RESULTS: In the cohort of 396 people, 39 met criteria for CAPA. Patients with CAPA were more likely than those without CAPA to have underlying pulmonary vascular disease (41% vs 21.6%, respectively; P = .01), liver disease (35.9% vs 18.2%; P = .02), coagulopathy (51.3% vs 33.1%; P = .03), solid tumors (25.6% vs 10.9%; P = .02), multiple myeloma (5.1% vs 0.3%; P = .03), and corticosteroid exposure during the index admission (66.7% vs 42.6%; P = .005), and had lower body mass indexes (median, 26.6 vs 29.9 [calculated as weight in kilograms divided by height in meters squared]; P = .04). Patients with CAPA had worse outcomes, as measured by ordinal severity of disease scores, requiring longer time to improvement (adjusted odds ratio, 1.081.091.1; P < .001), and advancing in severity almost twice as quickly (subhazard ratio, 1.31.82.5; P < .001). They were intubated twice as long as those without CAPA (subhazard ratio, 0.40.50.6; P < .001) and had longer hospital stays (median [interquartile range], 41.1 [20.5-72.4) vs 18.5 [10.7-31.8] days; P < .001). CONCLUSION: CAPA is associated with poor outcomes. Attention to preventive measures (screening and/or prophylaxis) is warranted in people with high risk of CAPA.


Asunto(s)
COVID-19 , Aspergilosis Pulmonar Invasiva , Aspergilosis Pulmonar , Adulto , Humanos , Aspergilosis Pulmonar Invasiva/diagnóstico , Aspergilosis Pulmonar Invasiva/epidemiología , Respiración Artificial/efectos adversos , Estudios Retrospectivos , SARS-CoV-2
3.
Am J Transplant ; 22(3): 853-864, 2022 03.
Artículo en Inglés | MEDLINE | ID: mdl-34741800

RESUMEN

Liver transplantation (LT) from donors-with-HIV to recipients-with-HIV (HIV D+/R+) is permitted under the HOPE Act. There are only three international single-case reports of HIV D+/R+ LT, each with limited follow-up. We performed a prospective multicenter pilot study comparing HIV D+/R+ to donors-without-HIV to recipients-with-HIV (HIV D-/R+) LT. We quantified patient survival, graft survival, rejection, serious adverse events (SAEs), human immunodeficiency virus (HIV) breakthrough, infections, and malignancies, using Cox and negative binomial regression with inverse probability of treatment weighting. Between March 2016-July 2019, there were 45 LTs (8 simultaneous liver-kidney) at 9 centers: 24 HIV D+/R+, 21 HIV D-/R+ (10 D- were false-positive). The median follow-up time was 23 months. Median recipient CD4 was 287 cells/µL with 100% on antiretroviral therapy; 56% were hepatitis C virus (HCV)-seropositive, 13% HCV-viremic. Weighted 1-year survival was 83.3% versus 100.0% in D+ versus D- groups (p = .04). There were no differences in one-year graft survival (96.0% vs. 100.0%), rejection (10.8% vs. 18.2%), HIV breakthrough (8% vs. 10%), or SAEs (all p > .05). HIV D+/R+ had more opportunistic infections, infectious hospitalizations, and cancer. In this multicenter pilot study of HIV D+/R+ LT, patient and graft survival were better than historical cohorts, however, a potential increase in infections and cancer merits further investigation.


Asunto(s)
Infecciones por VIH , Hepatitis C , Trasplante de Hígado , Estudios de Seguimiento , Supervivencia de Injerto , Infecciones por VIH/complicaciones , Humanos , Trasplante de Hígado/efectos adversos , Proyectos Piloto , Estudios Prospectivos , Donantes de Tejidos
4.
Transpl Infect Dis ; 23(4): e13687, 2021 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-34251742

RESUMEN

BACKGROUND: Few options are available for cytomegalovirus (CMV) treatment in transplant recipients resistant, refractory, or intolerant to approved agents. Letermovir (LET) is approved for prophylaxis in hematopoietic cell transplant (HCT) recipients, but little is known about efficacy in CMV infection. We conducted an observational study to determine the patterns of use and outcome of LET treatment of CMV infection in transplant recipients. METHODS: Patients who received LET for treatment of CMV infection were identified at 13 transplant centers. Demographic and outcome data were collected. RESULTS: Twenty-seven solid organ and 21 HCT recipients (one dual) from 13 medical centers were included. Forty-five of 47 (94%) were treated with other agents prior to LET, and 57% had a history of prior CMV disease. Seventy-seven percent were intolerant to other antivirals; 32% were started on LET because of resistance concerns. Among 37 patients with viral load < 1000 international units (IU)/ml at LET initiation, two experienced >1 log rise in viral load by week 12, and no deaths were attributed to CMV. Ten patients had viral load > 1000 IU/ml at LET initiation, and six of 10 (60%) had a CMV viral load < 1000 IU/ml at completion of therapy or last known value. LET was discontinued in two patients for an adverse event. CONCLUSIONS: Patients treated with LET with viral load < 1000 IU/ml had good virologic outcomes. Outcomes were mixed when LET was initiated at higher viral loads. Further studies on combination therapy or alternative LET dosing are needed.


Asunto(s)
Infecciones por Citomegalovirus , Trasplante de Células Madre Hematopoyéticas , Acetatos/uso terapéutico , Antivirales/uso terapéutico , Infecciones por Citomegalovirus/tratamiento farmacológico , Trasplante de Células Madre Hematopoyéticas/efectos adversos , Humanos , Quinazolinas , Receptores de Trasplantes , Carga Viral
5.
Transplant Direct ; 7(2): e656, 2021 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-33490381

RESUMEN

BACKGROUND: Donor-derived cell-free DNA (dd-cfDNA) is a useful biomarker of rejection that originates from allograft cells undergoing injury. Plasma levels <1% in kidney transplant recipients have a high negative predictive value for active allograft rejection. The utility of this biomarker in kidney transplant recipients receiving immune checkpoint inhibitor therapy is unknown. METHODS: We describe a case in which serial dd-cfDNA monitoring facilitated the use of immune checkpoint inhibitor therapy, which is known to be associated with high rates of rejection, in a kidney transplant recipient with metastatic cancer. RESULTS: A 72-y-old man with end-stage kidney disease secondary to autosomal dominant polycystic kidney disease underwent living unrelated kidney transplant in December 2010. His immunosuppression regimen included tacrolimus, mycophenolate, and prednisone. In July 2017, he presented with metastatic cutaneous squamous cell carcinoma. After his disease progressed through radiation therapy and cetuximab, he received pembrolizumab (antiprogrammed cell death protein 1). His dd-cfDNA level was undetectable at baseline, then increased during treatment but remained <1%. This trend, despite fluctuations in serum creatinine levels during therapy, allowed for continuation of pembrolizumab and successful treatment of his metastatic cancer without clinically evident allograft rejection. After discontinuation of pembrolizumab, dd-cfDNA levels fell below the level of detection. Genetic analysis of the cutaneous squamous cell carcinoma demonstrated a genetic profile distinct from the dd-cfDNA, indicating that tumor lysis did not impact increases in dd-cfDNA. CONCLUSIONS: Serial dd-cfDNA measurements may provide a useful, noninvasive biomarker for detecting allograft injury that may facilitate the use of immunomodulatory therapies in organ transplant recipients with cancer.

6.
Am J Transplant ; 21(5): 1754-1764, 2021 05.
Artículo en Inglés | MEDLINE | ID: mdl-32701209

RESUMEN

HIV-positive donor to HIV-positive recipient (HIV D+/R+) transplantation is permitted in the United States under the HIV Organ Policy Equity Act. To explore safety and the risk attributable to an HIV+ donor, we performed a prospective multicenter pilot study comparing HIV D+/R+ vs HIV-negative donor to HIV+ recipient (HIV D-/R+) kidney transplantation (KT). From 3/2016 to 7/2019 at 14 centers, there were 75 HIV+ KTs: 25 D+ and 50 D- (22 recipients from D- with false positive HIV tests). Median follow-up was 1.7 years. There were no deaths nor differences in 1-year graft survival (91% D+ vs 92% D-, P = .9), 1-year mean estimated glomerular filtration rate (63 mL/min D+ vs 57 mL/min D-, P = .31), HIV breakthrough (4% D+ vs 6% D-, P > .99), infectious hospitalizations (28% vs 26%, P = .85), or opportunistic infections (16% vs 12%, P = .72). One-year rejection was higher for D+ recipients (50% vs 29%, HR: 1.83, 95% CI 0.84-3.95, P = .13) but did not reach statistical significance; rejection was lower with lymphocyte-depleting induction (21% vs 44%, HR: 0.33, 95% CI 0.21-0.87, P = .03). In this multicenter pilot study directly comparing HIV D+/R+ with HIV D-/R+ KT, overall transplant and HIV outcomes were excellent; a trend toward higher rejection with D+ raises concerns that merit further investigation.


Asunto(s)
Infecciones por VIH , Trasplante de Riñón , Estudios de Seguimiento , Rechazo de Injerto/etiología , Supervivencia de Injerto , Infecciones por VIH/complicaciones , Humanos , Proyectos Piloto , Estudios Prospectivos , Factores de Riesgo , Donantes de Tejidos
7.
Clin Infect Dis ; 70(2): 252-261, 2020 01 02.
Artículo en Inglés | MEDLINE | ID: mdl-30855688

RESUMEN

BACKGROUND: Cryptococcosis is increasingly recognized in people without human immunodeficiency virus (HIV). METHODS: A multicenter, prospective cohort study was performed in 25 US centers. Consenting patients were prospectively followed for ≤2 years. Neurological morbidities were assessed with longitudinal event depiction and functional scores (Montreal Cognitive Assessment [MoCA]). Risks of death were analyzed using Cox regression. RESULTS: One hundred forty-five subjects were enrolled. Most were male (95; 65.5%) and had immunosuppression (120; 82.8%), including solid organ transplant (SOT; 33.8%), autoimmunity (15.9%), and hematologic malignancies (11.7%). Disease involved the central nervous system (CNS) in 71 subjects (49%). Fever was uncommon, documented in 40 (27.8%) subjects, and absence was associated with diagnostic delay (mean: 48.2 vs 16.5 days; P = .007). Abnormal MoCA scores (<26) were predictive of CNS disease; low scores (<22) were associated with poor long-term cognition. Longitudinal event depiction demonstrated frequent complications in people with CNS disease; 25 subjects (35.2%) required >1 lumbar puncture and 8 (11.3%) required ventriculostomies. In multivariable models, older age (>60 years) was associated with higher risks of death (hazard ratio [HR], 2.14; 95% confidence interval [CI], 1.05-4.38; P = .036), and lower risks were noted with underlying hematologic malignancy (HR, 0.29; 95% CI, 0.09-0.98; P = .05) and prior SOT (HR, 0.153; 95% CI, 0.05-0.44; P = .001). CONCLUSIONS: Despite aggressive antifungal therapies, outcomes of CNS cryptococcosis in people without HIV are characterized by substantial long-term neurological sequelae. Studies are needed to understand mechanism(s) of cognitive decline and to enable better treatment algorithms.


Asunto(s)
Criptococosis , Diagnóstico Tardío , Anciano , Estudios de Cohortes , Criptococosis/epidemiología , VIH , Humanos , Estudios Longitudinales , Masculino , Estudios Prospectivos , Estados Unidos/epidemiología
8.
Am J Transplant ; 18(10): 2579-2586, 2018 10.
Artículo en Inglés | MEDLINE | ID: mdl-29947471

RESUMEN

Organs from deceased donors with suspected false-positive HIV screening tests were generally discarded due to the chance that the test was truly positive. However, the HIV Organ Policy Equity (HOPE) Act now facilitates use of such organs for transplantation to HIV-infected (HIV+) individuals. In the HOPE in Action trial, donors without a known HIV infection who unexpectedly tested positive for anti-HIV antibody (Ab) or HIV nucleic acid test (NAT) were classified as suspected false-positive donors. Between March 2016 and March 2018, 10 suspected false-positive donors had organs recovered for transplant for 21 HIV + recipients (14 single-kidney, 1 double-kidney, 5 liver, 1 simultaneous liver-kidney). Median donor age was 24 years; cause of death was trauma (n = 5), stroke (n = 4), and anoxia (n = 1); three donors were labeled Public Health Service increased infectious risk. Median kidney donor profile index was 30.5 (IQR 22-58). Eight donors were HIV Ab+/NAT-; two were HIV Ab-/NAT+. All 10 suspected false-positive donors were confirmed to be HIV-noninfected. Given the false-positive rates of approved assays used to screen > 20 000 deceased donors annually, we estimate 50-100 HIV false-positive donors per year. Organ transplantation from suspected HIV false-positive donors is an unexpected benefit of the HOPE Act that provides another novel organ source.


Asunto(s)
Infecciones por VIH/cirugía , VIH/aislamiento & purificación , Trasplante de Órganos , Donantes de Tejidos/provisión & distribución , Obtención de Tejidos y Órganos/estadística & datos numéricos , Adolescente , Adulto , Cadáver , Niño , Reacciones Falso Positivas , Femenino , Estudios de Seguimiento , Infecciones por VIH/diagnóstico , Infecciones por VIH/virología , Humanos , Masculino , Tamizaje Masivo , Persona de Mediana Edad , Pronóstico , Estudios Prospectivos , Pruebas Serológicas , Obtención de Tejidos y Órganos/normas , Adulto Joven
9.
Clin Infect Dis ; 67(11): 1705-1711, 2018 11 13.
Artículo en Inglés | MEDLINE | ID: mdl-29684106

RESUMEN

Background: Establishing rapid diagnoses of invasive aspergillosis (IA) is a priority tests that detect galactomannan and ß-d-glucan are available, but are technically cumbersome and rely on invasive sampling (blood or bronchoalveolar lavage). Methods: We optimized a lateral flow dipstick assay using the galactofuranose-specific monoclonal antibody (mAb476), which recognizes urine antigens after Aspergillus fumigatus pulmonary infection in animals. Urine samples were obtained from a cohort of 78 subjects undergoing evaluation for suspected invasive fungal infections, and stored frozen until testing. Urine was processed by centrifugation through desalting columns and exposed to dipsticks. Reviewers blinded to clinical diagnoses graded results. Western blots were performed on urine samples from 2 subjects to characterize mAb476-reactive antigens. Results: Per-patient sensitivity and specificity for diagnosis of proven or probable IA in the overall cohort was 80% (95% confidence interval [CI], 61.4%-92.3%) and 92% (95% CI, 74%-99%), respectively. In the subgroup with cancer, sensitivity was 89.5% (95% CI, 66.7%-98.7%) and specificity was 90.9% (95% CI, 58.7%-99.8%); among all others, sensitivity and specificity were 63.6% (95% CI, 30.8%-89.1%) and 92.9% (95% CI, 66.1%-99.8%), respectively. Eliminating lung transplant recipients with airway disease increased sensitivity in the noncancer cohort (85.7% [95% CI, 42.1%-99.6%]). Semiquantitative urine assay results correlated with serum galactomannan indices. Western blots demonstrated mAb476-reactive antigens in urine from cases, ranging between 26 kDa and 35 kDa in size. Conclusions: Urine testing using mAb476 may be used as an aid to diagnose IA in high-risk patients.


Asunto(s)
Antígenos Fúngicos/orina , Aspergilosis Pulmonar Invasiva/diagnóstico , Aspergilosis Pulmonar Invasiva/orina , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Anticuerpos Monoclonales/inmunología , Niño , Estudios de Cohortes , Galactosa/análogos & derivados , Humanos , Inmunoensayo , Mananos/sangre , Persona de Mediana Edad , Tiras Reactivas , Sensibilidad y Especificidad , Adulto Joven
10.
Transplantation ; 100(10): e74-80, 2016 10.
Artículo en Inglés | MEDLINE | ID: mdl-27495775

RESUMEN

BACKGROUND: Antiviral-resistant or refractory cytomegalovirus (CMV) infection is challenging, and salvage therapies, foscarnet, and cidofovir, have significant toxicities. Several investigational anti-CMV agents are under development, but more information is needed on outcomes of current treatments to facilitate clinical trial design for new drugs. METHODS: Records of solid organ transplant (SOT) and hematopoietic cell transplant (HCT) recipients at a single center over a 10-year period were reviewed retrospectively to characterize those who had received foscarnet treatment for ganciclovir-resistant or refractory CMV infection. Data were collected on virologic responses, mortality, and nephrotoxicity. RESULTS: Of 39 patients (22 SOT, 17 HCT), 15 had documented ganciclovir resistance mutations and 11 (28%) of 39 had tissue-invasive CMV. Median duration of foscarnet was 32 days. Virologic failure occurred in 13 (33%) of 39 and relapses of viremia occurred in 31%. Mortality was 12 (31%) of 39 and was higher in HCT than SOT (P = 0.001), although ganciclovir resistance was more common in SOT (P = 0.003). Doses of ganciclovir or valganciclovir were low in 10 (26%) of 39 at some time before switching to foscarnet. Renal dysfunction occurred in 20 (51%) of 39 by end of treatment and in 7 (28%) of 25 after 6 months. CONCLUSIONS: Outcomes of existing treatment for ganciclovir-resistant or refractory CMV are suboptimal, in terms of virologic clearance, renal dysfunction, and mortality. These data should provide background information for future clinical trials of newer antiviral agents.


Asunto(s)
Antivirales/uso terapéutico , Infecciones por Citomegalovirus/tratamiento farmacológico , Foscarnet/uso terapéutico , Ganciclovir/uso terapéutico , Adolescente , Adulto , Anciano , Niño , Infecciones por Citomegalovirus/mortalidad , Infecciones por Citomegalovirus/virología , Farmacorresistencia Viral , Femenino , Foscarnet/efectos adversos , Ganciclovir/efectos adversos , Trasplante de Células Madre Hematopoyéticas , Humanos , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Receptores de Trasplantes
11.
Diagn Microbiol Infect Dis ; 75(2): 144-9, 2013 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-23142166

RESUMEN

This is a retrospective, single-center study of adult patients with newly diagnosed acute myelogenous leukemia (AML), who received intensive induction timed sequential chemotherapy from 1/2005 to 6/2010. Among 254 consecutive AML patients, 123 (48.4%) developed an invasive fungal infection (IFI): 14 (5.5%) patients with invasive candidiasis (IC) and 108 (42.5%) patients with invasive mould infections (IMI). Among 108 IMI identified, 4 (3.7%) were proven, 1 (0.9%) probable, and 103 (95.4%) were possible, using current definitions. Overall, 6-month mortality was 23.7% (27/114) and 20.6% (26/126) for patients with and without an IFI, respectively. Older age (≥50 years; hazard ratio [HR]: 2.5, P < 0.001), female gender (HR: 1.7, P = 0.006), and baseline renal and/or liver dysfunction (HR: 2.4, P < 0.001) were the strongest mortality predictors. We report relatively low rates of IC despite lack of routine primary antifungal prophylaxis, albeit associated with poor long-term survival. High rates of IMI, the vast majority with a possible diagnosis, were observed. Host-related variables (demographics and baseline organ dysfunction) were identified as the most significant risk factors for IFI and mortality predictors in this series.


Asunto(s)
Leucemia Mieloide Aguda/tratamiento farmacológico , Leucemia Mieloide Aguda/microbiología , Micosis/complicaciones , Adulto , Anciano , Femenino , Fiebre/sangre , Fiebre/microbiología , Humanos , Quimioterapia de Inducción , Estimación de Kaplan-Meier , Leucemia Mieloide Aguda/epidemiología , Masculino , Persona de Mediana Edad , Micosis/epidemiología , Neutropenia/microbiología , Estudios Retrospectivos , Factores de Riesgo , Estadísticas no Paramétricas , Resultado del Tratamiento
12.
Clin Infect Dis ; 54(7): 913-21, 2012 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-22267716

RESUMEN

BACKGROUND: The intravenous use of voriconazole requires coadministration with sulphobutylether-ß-cyclodextrin, which may accumulate in patients with impaired renal function. METHODS: All adult patients treated with the same formulation of voriconazole for a minimum of 3 consecutive days were included. Renal function was assessed based on the creatinine level and the calculated creatinine clearance (CrCl). Change in renal function was calculated on days 3, 7, and end of treatment (EOT) and was defined based on the RIFLE criteria. RESULTS: Among 166 patients in whom baseline renal function was assessed, 42 (25.3%) had a CrCl <50 mL/min and received intravenous voriconazole, 77 (46.4%) had a CrCl ≥50 mL/min and received intravenous voriconazole, and 47 (28.3%) had a CrCl <50 mL/min and were treated with oral voriconazole. Renal function changed on days 3, 7, and EOT in 19 (11.4%), 14 (8.4%), and 28 (16.9%) patients, respectively. Multivariate analyses identified significant predictors of renal dysfunction: (1) day 3, hematologic malignancy (odds ratio [OR], 5.09, P = .01), fluconazole use within 30 days prior to voriconazole (OR, 6.21; P = .008), coadministration of penicillins (OR, 6.12; P = .03), and immunosuppressants (OR, 7.00; P = .002); (2) day 7, baseline liver impairment (OR, 5.30; P value = .004); (3) EOT, administration of penicillins (OR, 2.39; P = .04). CONCLUSIONS: Voriconazole route of administration and baseline renal function were not predictors of worsening renal dysfunction on days 3, 7, and EOT. Underlying disease, baseline liver impairment, and concomitant administration of other drugs (eg, penicillins, fluoroquinolones, immunosuppressants) were the strongest predictors of renal dysfunction.


Asunto(s)
Antifúngicos/administración & dosificación , Antifúngicos/efectos adversos , Enfermedades Renales/complicaciones , Micosis/tratamiento farmacológico , Pirimidinas/administración & dosificación , Pirimidinas/efectos adversos , Insuficiencia Renal/inducido químicamente , Triazoles/administración & dosificación , Triazoles/efectos adversos , Adulto , Anciano , Anciano de 80 o más Años , Creatinina/metabolismo , Femenino , Humanos , Infusiones Intravenosas , Enfermedades Renales/fisiopatología , Masculino , Tasa de Depuración Metabólica , Persona de Mediana Edad , Estudios Retrospectivos , Voriconazol , Adulto Joven
13.
J Biol Chem ; 277(38): 34978-86, 2002 Sep 20.
Artículo en Inglés | MEDLINE | ID: mdl-12105205

RESUMEN

The Saccharomyces cerevisiae CKI-encoded choline kinase is phosphorylated on a serine residue and stimulated by protein kinase A. We examined the hypothesis that amino acids Ser(30) and Ser(85) contained in a protein kinase A sequence motif in choline kinase are target sites for protein kinase A. The synthetic peptides SQRRHSLTRQ (V(max)/K(m) = 10.8 microm(-1) nmol min(-1) mg(-1)) and GPRRASATDV (V(max)/K(m) = 0.15 microm(-1) nmol min(-1) mg(-1)) containing the protein kinase A motif for Ser(30) and Ser(85), respectively, within the choline kinase protein were substrates for protein kinase A. Choline kinase with Ser(30) to Ala (S30A) and Ser(85) to Ala (S85A) mutations were constructed alone and in combination by site-directed mutagenesis and expressed in a cki1Delta eki1Delta double mutant that lacks choline kinase activity. The mutant enzymes were expressed normally, but the specific activity of choline kinase in cells expressing the S30A, S85A, and S30A,S85A mutant enzymes was reduced by 44, 8, and 60%, respectively, when compared with the control. In vivo labeling experiments showed that the extent of phosphorylation of the S30A, S85A, and S30A,S85A mutant enzymes was reduced by 70, 17, and 83%, respectively. Phosphorylation of the S30A, S85A, and S30A,S85A mutant enzymes by protein kinase A in vitro was reduced by 60, 7, and 96%, respectively, and peptide mapping analysis of the mutant enzymes confirmed the phosphorylation sites in the enzyme. The incorporation of (3)H-labeled choline into phosphocholine and phosphatidylcholine in cells bearing the S30A, S85A, and S30A,S85A mutant enzymes was reduced by 56, 27, and 81%, respectively, and by 58, 33, and 84%, respectively, when compared with control cells. These data supported the conclusion that phosphorylation of choline kinase on Ser(30) and Ser(85) by protein kinase A regulates PC synthesis by the CDP-choline pathway.


Asunto(s)
Colina Quinasa/metabolismo , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Citidina Difosfato Colina/metabolismo , Fosfatidilcolinas/biosíntesis , Saccharomyces cerevisiae/enzimología , Serina/metabolismo , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Secuencia de Bases , Colina Quinasa/química , Colina Quinasa/genética , Cartilla de ADN , Mutagénesis Sitio-Dirigida , Fosforilación , Especificidad por Sustrato
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