Iron chaperones PCBP1 and PCBP2 mediate the metallation of the dinuclear iron enzyme deoxyhypusine hydroxylase.

Although cells express hundreds of metalloenzymes, the mechanisms by which apoenzymes receive their metal cofactors are largely unknown. Poly(rC)-binding proteins PCBP1 and PCBP2 are multifunctional adaptor proteins that bind iron and deliver it to ferritin for storage or to prolyl and asparagyl hydroxylases to metallate the mononuclear iron center. Here, we show that PCBP1 and PCBP2 also deliver iron to deoxyhypusine hydroxylase (DOHH), the dinuclear iron enzyme required for hypusine modification of the translation factor eukaryotic initiation factor 5A. Cells depleted of PCBP1 or PCBP2 exhibited loss of DOHH activity and loss of the holo form of the enzyme in cells, particularly when cells were made mildly iron-deficient. Lysates containing PCBP1 and PCBP2 converted apo-DOHH to holo-DOHH in vitro with greater efficiency than lysates lacking PCBP1 or PCBP2. PCBP1 bound to DOHH in iron-treated cells but not in control or iron-deficient cells. Depletion of PCBP1 or PCBP2 had no effect on the cytosolic Fe-S cluster enzyme xanthine oxidase but led to loss of cytosolic aconitase activity. Loss of aconitase activity was not accompanied by gain of RNA-binding activity, a pattern suggesting the incomplete disassembly of the [4Fe-4S] cluster. PCBP depletions had minimal effects on total cellular iron, mitochondrial iron levels, and heme synthesis. Thus, PCBP1 and PCBP2 may serve as iron chaperones to multiple classes of cytosolic nonheme iron enzymes and may have a particular role in restoring metal cofactors that are spontaneously lost in iron deficient cells.

Late-stage maturation of the Rieske Fe/S protein: Mzm1 stabilizes Rip1 but does not facilitate its translocation by the AAA ATPase Bcs1.

The final step in the assembly of the ubiquinol-cytochrome c reductase or bc(1) complex involves the insertion of the Rieske Fe/S cluster protein, Rip1. Maturation of Rip1 occurs within the mitochondrial matrix prior to its translocation across the inner membrane (IM) in a process mediated by the Bcs1 ATPase and subsequent insertion into the bc(1) complex. Here we show that the matrix protein Mzm1 functions as a Rip1 chaperone, stabilizing Rip1 prior to the translocation step. In the absence of Mzm1, Rip1 is prone to either proteolytic degradation or temperature-induced aggregation. A series of Rip1 truncations were engineered to probe motifs necessary for Mzm1 interaction and Bcs1-mediated translocation of Rip1. The Mzm1 interaction with Rip1 persists in Rip1 variants lacking its transmembrane domain or containing only its C-terminal globular Fe/S domain. Replacement of the globular domain of Rip1 with that of the heterologous folded protein Grx3 abrogated Mzm1 interaction; however, appending the C-terminal 30 residues of Rip1 to the Rip1-Grx3 chimera restored Mzm1 interaction. The Rip1-Grx3 chimera and a Rip1 truncation containing only the N-terminal 92 residues each induced stabilization of the bc(1):cytochrome oxidase supercomplex in a Bcs1-dependent manner. However, the Rip1 variants were not stably associated with the supercomplex. The induced supercomplex stabilization by the Rip1 N terminus was independent of Mzm1.

Reprint of: Biogenesis of the cytochrome bc(1) complex and role of assembly factors.

The cytochrome bc(1) complex is an essential component of the electron transport chain in most prokaryotes and in eukaryotic mitochondria. The catalytic subunits of the complex that are responsible for its redox functions are largely conserved across kingdoms. In eukarya, the bc(1) complex contains supernumerary subunits in addition to the catalytic core, and the biogenesis of the functional bc(1) complex occurs as a modular assembly pathway. Individual steps of this biogenesis have been recently investigated and are discussed in this review with an emphasis on the assembly of the bc(1) complex in the model eukaryote Saccharomyces cerevisiae. Additionally, a number of assembly factors have been recently identified. Their roles in bc(1) complex biogenesis are described, with special emphasis on the maturation and topogenesis of the yeast Rieske iron-sulfur protein and its role in completing the assembly of functional bc(1) complex. This article is part of a Special Issue entitled: Biogenesis/Assembly of Respiratory Enzyme Complexes.

Structure, function, and assembly of heme centers in mitochondrial respiratory complexes.

The sequential flow of electrons in the respiratory chain, from a low reduction potential substrate to O(2), is mediated by protein-bound redox cofactors. In mitochondria, hemes-together with flavin, iron-sulfur, and copper cofactors-mediate this multi-electron transfer. Hemes, in three different forms, are used as a protein-bound prosthetic group in succinate dehydrogenase (complex II), in bc(1) complex (complex III) and in cytochrome c oxidase (complex IV). The exact function of heme b in complex II is still unclear, and lags behind in operational detail that is available for the hemes of complex III and IV. The two b hemes of complex III participate in the unique bifurcation of electron flow from the oxidation of ubiquinol, while heme c of the cytochrome c subunit, Cyt1, transfers these electrons to the peripheral cytochrome c. The unique heme a(3), with Cu(B), form a catalytic site in complex IV that binds and reduces molecular oxygen. In addition to providing catalytic and electron transfer operations, hemes also serve a critical role in the assembly of these respiratory complexes, which is just beginning to be understood. In the absence of heme, the assembly of complex II is impaired, especially in mammalian cells. In complex III, a covalent attachment of the heme to apo-Cyt1 is a prerequisite for the complete assembly of bc(1), whereas in complex IV, heme a is required for the proper folding of the Cox 1 subunit and subsequent assembly. In this review, we provide further details of the aforementioned processes with respect to the hemes of the mitochondrial respiratory complexes. This article is part of a Special Issue entitled: Cell Biology of Metals.

Biogenesis of the cytochrome bc(1) complex and role of assembly factors.

The cytochrome bc(1) complex is an essential component of the electron transport chain in most prokaryotes and in eukaryotic mitochondria. The catalytic subunits of the complex that are responsible for its redox functions are largely conserved across kingdoms. In eukarya, the bc(1) complex contains supernumerary subunits in addition to the catalytic core, and the biogenesis of the functional bc(1) complex occurs as a modular assembly pathway. Individual steps of this biogenesis have been recently investigated and are discussed in this review with an emphasis on the assembly of the bc(1) complex in the model eukaryote Saccharomyces cerevisiae. Additionally, a number of assembly factors have been recently identified. Their roles in bc(1) complex biogenesis are described, with special emphasis on the maturation and topogenesis of the yeast Rieske iron-sulfur protein and its role in completing the assembly of functional bc(1) complex. This article is part of a Special Issue entitled: Biogenesis/Assembly of Respiratory Enzyme Complexes.

Satisfaction with quality of life poststroke: effect of sex differences in pain response.

OBJECTIVE: To study the relationship between sex differences among men and women in the response to pain and the effect on satisfaction with quality of life (QOL) in poststroke patients approximately 90 days after discharge from inpatient medical rehabilitation. DESIGN: Cross-sectional design. SETTING: Community based. PARTICIPANTS: The sample included 1724 patients (877 men, 847 women) aged 40 years and older with a history of stroke, according to information obtained from the IT HealthTrack database. The average age was 68.7 years; 79.3% were non-Hispanic white. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Satisfaction with QOL. RESULTS: Pain ratings for both the men and the women were significant and inversely associated with satisfaction with QOL after adjustments for possible confounding factors. However, among men with stroke, each 1-point increase in pain rating was associated with an 18% decreased odds of being satisfied with QOL (odds ratio [OR], .81; 95% confidence interval [CI], .77-.86). Conversely, among women with stroke, each 1-point increase in pain rating was associated with an 11% decreased odds of being satisfied with QOL (OR=.89; 95% CI, .84-.95). CONCLUSIONS: Our data indicate that pain after stroke is significantly associated with reduced satisfaction with QOL, particularly among men. Increased awareness and treatment of pain may improve satisfaction with QOL. Our findings suggest that sex differences and pain response are clinically important factors in examining satisfaction with QOL in the poststroke population.

Perceived pain and satisfaction with medical rehabilitation after hospital discharge.

OBJECTIVE: To examine the association between pain and satisfaction with medical rehabilitation in patients with hip or knee replacement approximately 90 days after discharge from inpatient medical rehabilitation. DESIGN: A cross-sectional design. PARTICIPANTS: The sample included 2507 patients with hip or knee replacement using information from the IT Health Track medical outcome database. MAIN OUTCOME MEASURE: Satisfaction with medical rehabilitation. RESULTS: The average age was 70.2 years, 66.5% were female, and 88.5% were non-Hispanic white. Pain scores were significantly and inversely associated with satisfaction with medical rehabilitation after adjustment for possible confounding factors. In patients with hip replacement each one-point increase in pain score was associated with a 10% decreased odds ratio (OR) of being satisfied with medical rehabilitation (OR 0.90, 95% confidence interval (CI) 0.84, 0.96). In patients with knee replacement, each one-point increase in pain score was associated with a 9% decreased odds ratio (OR 0.91, 95% CI 0.87, 0.96) of being satisfied with medical rehabilitation. CONCLUSION: Our data indicate that postoperative pain from hip or knee replacement is associated with reduced satisfaction with medical rehabilitation. Better postoperative pain control may improve a patient's level of satisfaction.

The influence of perceived pain on satisfaction with community participation after hospital discharge.

OBJECTIVE: To examine the association between pain and satisfaction with community participation for patients with stroke approximately 4 months after discharge from inpatient medical rehabilitation. DESIGN: A cross-sectional study from 2001 to 2002 using information from the IT HealthTrack database. SETTING: Community based. PARTICIPANTS: The study included 1673 patients with stroke aged 40 years or older discharged from inpatient medical rehabilitation. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Primary measures included pain ratings and satisfaction with community participation. RESULTS: The sample was 49.4% female and 81.1% non-Hispanic white. One third of the sample reported mild to severe pain. Pain ratings showed a significant and inverse association with satisfaction with community participation. The association remained significant with adjustment for possible confounding factors and with stratification by right and left body involvement. Each 1-level increase in pain rating score (range, 0-10) was associated with a 12% decreased odds ratio (OR=.88; 95% confidence interval, .84-.93) of being satisfied with community participation after adjustment for age, sex, marital status, ethnicity, and motor and cognitive functional status. CONCLUSIONS: In persons with stroke, high pain rating scores were significantly associated with lower satisfaction with community participation. Effective pain management may increase level of satisfaction with community participation in persons with stroke.

Reliability of the positive and negative affect schedule (PANAS) in medical rehabilitation.

OBJECTIVE: To examine the reliability of the Positive and Negative Affect Schedule (PANAS) in patients 90 and 100 days after discharge from inpatient medical rehabilitation. DESIGN: A prospective study. SUBJECTS: A convenience sample of 31 medical rehabilitation patients. MAIN MEASURES: The PANAS. RESULTS: The average age was 74 years, 80.7% were female and the average length of stay was 13 days. The test-retest intraclass correlation (ICC) values for the positive and negative affect scales (at the 90 and 100 day follow-up assessment) were 0.79 and 0.93, respectively. CONCLUSIONS: Our results show that the PANAS has excellent reliability among a sample of patients who received inpatient medical rehabilitation.

Orthopedic impairment after medical rehabilitation: functional performance and satisfaction with community participation.

OBJECTIVE: To determine the prevalence of satisfaction with community participation and to examine associations between change in functional status and satisfaction with community participation for persons with orthopedic impairments. DESIGN: Retrospective study of 3832 patients discharged from medical rehabilitation facilities in 2001 using information from the IT Health Track database. RESULTS: Primary measures were the FIM instrument and satisfaction with community participation. The majority of patients (86.9%) were satisfied (very or somewhat) with their level of community participation. Positive-change scores in FIM total from admission to the 80- to 180-day follow-up were associated with an 8% increased odds of being in a higher satisfaction with community participation level (odds ratio, 1.08; 95% confidence interval: 1.07, 1.09) after controlling for age, gender, marital status, race/ethnicity, insurance source, length of stay and functional status. Similarly, positive-change score in motor (odds ratio, 1.09; 95% confidence interval: 1.08, 1.10) and cognition (odds ratio, 1.26; 95% confidence interval: 1.19, 1.32) FIM measures from admission to follow-up were associated with greater satisfaction with community participation. CONCLUSION: Gains in functional status were significantly associated with greater satisfaction with community participation. Satisfaction with community participation provides information useful to evaluate patient recovery after discharge from inpatient medical rehabilitation.

Modality effects in compounding with English inflectional morphology.

The treatment of plural morphemes in English noun-noun compounds is significant because it provides a test case for competing theories of language acquisition and representation. Even when the first noun in a compound refers to plural items, native speakers frequently use the singular form (Murphy, 2000). Sometimes, they will use the irregular plural form ('mice chaser') but very rarely are regular plurals ('rats chaser') used as the first noun in a compound. This effect has been found with native English-speaking children (Gordon, 1985; Nicoladis, 2000; Oetting & Rice, 1993; van der Lely & Christian, 2000); native English-speaking teenagers (van der Lely & Christian, 2000); and native English-speaking adults (Lardiere & Schwartz, 1997; Murphy, 2000). The apparent dissociation between regular and irregular plurals (i.e.that irregular plurals are included before a second noun but regular plurals are almost never included before a second noun) is thought to be due to innate morphological constraints (Marcus, Brinkmann, Clahsen, Weise, & Pinker, 1995). Such constraints predict that all items of regular morphology should be treated differently from all items of irregular morphology by language users in all situations. However, if external factors such as input and response modality affect the number of plurals included in compounds, then this questions the internal constraint-based explanations of compounding and encourages investigation of how external factors might influence the number of plurals included in compounds.

Functional status and satisfaction with community participation in persons with stroke following medical rehabilitation.

BACKGROUND AND AIMS: Researchers and policy-makers have recognized that quality of life assessments are essential to better understand the benefits of rehabilitation intervention. The purpose of the study was to examine associations between functional status and satisfaction with community participation for persons with stroke at 80-180 days after discharge from medical rehabilitation. METHODS: The study was retrospective, using data from the Information Technology (IT) Health-Track database for patients discharged from medical rehabilitation facilities in 2001/2002. The study population included 1870 persons with stroke aged 40 or older who had complete information at admission and follow-up (mean age at admission 68.3 yr, SD 14.5). The sample was 49.3% female and 72.6% were non-Hispanic white. RESULTS: Results showed a significant positive association between change in functional status (admission to follow-up) and satisfaction with community participation. Positive change ratings in functional status were associated with increased satisfaction with community participation (b = 0.02, SE = 0.001, p = 0.0001), after adjustment for age, gender, marital status, race/ethnicity, insurance source and functional status score at admission. Similarly, positive associations were observed for changes in motor and cognitive subscale ratings and satisfaction with community participation. The strongest association among six functional status domains and satisfaction with community participation was for communication (beta = 0.60) and social cognition (beta = 0.58). CONCLUSIONS: This study showed a statistically significant association between a modifiable factor (functional status) and a quality of life indicator (satisfaction with community participation). Results add to emerging literature on patient-centered outcomes and extend measures of recovery beyond functional status to include consumer satisfaction with a community outcome.

The F1-ATPase beta-subunit is the putative enterostatin receptor.

It has been suggested that the F1-ATPase beta-subunit is the enterostatin receptor. We investigated the binding activity of the purified protein with a labeled antagonist, beta-casomorphin1-7, in the absence and presence of cold enterostatin. 125I-beta-casomorphin1-7 weakly binds to the rat F1-ATPase beta-subunit. Binding was promoted by low concentrations of cold enterostatin but displaced by higher concentrations. To study the relationship between binding activity and feeding behavior, we examined the ability of a number of enterostatin analogs to affect beta-casomorphin1-7 binding to the F1-ATPase beta-subunit. Peptides that suppressed food intake promoted beta-casomorphin1-7 binding whereas peptides that stimulated food intake or did not affect the food intake displaced beta-casomorphin1-7 binding. Surface plasmon resonance measurements show that the beta-subunit of F1-ATPase binds immobilized enterostatin with a dissociation constant of 150 nM, where no binding could be detected for the assembled F1-ATPase complex. Western blot analysis showed the F1-ATPase beta-subunit was present on plasma and mitochondrial membranes of rat liver and amygdala. The data provides evidence that the F1-ATPase beta-subunit is the enterostatin receptor and suggests that enterostatin and beta-casomorphin1-7 bind to distinct sites on the protein.

Comparison of logistic regression and neural network analysis applied to predicting living setting after hip fracture.

PURPOSE: Describe and compare the characteristics of artificial neural networks and logistic regression to develop prediction models in epidemiological research. METHODS: The sample included 3708 persons with hip fracture from 46 different states included in the Uniform Data System for Medical Rehabilitation. Mean age was 75.5 years (sd=14.2), 73.7% of patients were female, and 82% were non-Hispanic white. Average length of stay was 17.0 days (sd=10.6). The primary outcome measure was living setting (at home vs. not at home) at 80 to 180 days after discharge. RESULTS: Statistically significant variables (p <.05) in the logistic model included follow-up therapy, sphincter control, self-care ability, marital status, age, and length of stay. Areas under the receiver operating characteristic curves were 0.67 for logistic regression and 0.73 for neural network analysis. Calibration curves indicated a slightly better fit for the neural network model. CONCLUSIONS: Follow-up therapy and independent bowel and/or bladder function were strong predictors of living at home up to 6 months after hospitalization for hip fracture. No practical differences were found between the predictive ability of logistic regression and neural network analysis in this sample.

Satisfaction with medical rehabilitation after spinal cord injury.

STUDY DESIGN: Retrospective. OBJECTIVE: To predict satisfaction with medical rehabilitation. SUMMARY OF BACKGROUND DATA: While spinal cord injury (SCI) patient satisfaction with life and community services has been investigated, satisfaction with medical rehabilitation has not. METHODS: Information submitted to the Uniform Data System for Medical Rehabilitation (1998-2001) by 134 hospitals/rehabilitation facilities in the United States (n = 6,205 patients with SCI) was examined. Predictors were sociodemographic variables, Case Mix Groupings (CMG) (401-505, 5001), length of stay, rehospitalization, follow-up therapy, and health maintenance. Satisfaction was assessed at a mean of 92.2 days (SD 11.9 days) postdischarge. Data were analyzed according to who reported the outcome (patient, n = 3,858 or family/other, n = 1,869). Statistical modeling was conducted using logistic regression. RESULTS: High overall satisfaction was reported (94%). Significant predictors for the patient report data were CMG and rehospitalization. Compared with CMG 5001 (short stay, <3 days), patients in CMGs 401/2/3 and 501/2/3/4/5 had a 54% to 74% lower likelihood of being dissatisfied. Rehospitalized patients had a higher likelihood of dissatisfaction (odds ratio 2.3, 95% confidence interval 1.7 to 3.2). Significant predictors for the family/other report data were CMG (compared to CMG 5001, CMGs 401/2, 403, and 501/2 had a 70% lower likelihood of dissatisfaction), rehospitalization (odds ratio 1.7, 95% confidence interval 1.1-2.5), and marital status (married = 50% lower likelihood of dissatisfaction, 95% confidence interval 0.26-0.96). CONCLUSIONS: Satisfaction with medical rehabilitation services following SCI is related to functional abilities, rehospitalization, and marital status. Slightly different results were found for whether satisfaction was rated by the patient or family/other. The complex relationships among satisfaction, patient demographics, and functional status require continued examination.

Effect of functional gain on satisfaction with medical rehabilitation after stroke.

OBJECTIVE: To examine the association between gain in motor and cognitive functional status with patient satisfaction 3-6 mo after rehabilitation discharge. DESIGN: Patient satisfaction and changes in functional status were examined in 18,375 patients with stroke who received inpatient medical rehabilitation. Information was obtained from 144 hospitals and rehabilitation facilities contributing records to the Uniform Data System for Medical Rehabilitation and the National Follow-up Services. RESULTS: Data analysis revealed significant (P < 0.05) differences in satisfaction responses based on whether information was collected from patient self-report or from a family member proxy, and the two subsets were analyzed separately. Logistic regression revealed the following significant predictors of satisfaction for data collected from stroke patients: cognitive and motor gain, rehospitalization, who the patient was living with at follow-up, age, and follow-up therapy. In the patient-reported data subset, compared with patients who showed improved cognitive or motor functional status, those with no change, respectively, had a 31% and 33% reduced risk of dissatisfaction. In addition, rehospitalized patients had a higher risk of dissatisfaction. For the proxy reported data subset, significant influences on satisfaction were health maintenance, rehospitalization, stroke type, ethnicity, cognitive FIM gain, length of stay, and follow-up therapy. CONCLUSIONS: Ratings of satisfaction with rehabilitation services were affected by change in functional status and whether the information was collected from patient rating or proxy response.

Disparity in health services and outcomes for persons with hip fracture and lower extremity joint replacement.

OBJECTIVE: Examine disparity in health services and outcomes for adults with a hip fracture or lower extremity joint replacement. MATERIALS AND METHODS: This study examined 28,522 patient records including 12,328 (mean age 76.6 years) with hip fracture and 16,194 (mean age 71.8 years) with joint replacement. RESULTS: Non-Hispanic white and black patients were significantly (P < 0.05) more likely to be discharged home alone and responsible for their own care than were Asian or Hispanic patients. Sixty-four percent of Hispanic patients received inpatient rehabilitation after hip fracture and 36% after hip or knee arthroplasty. In contrast, 58% of non-Hispanic white persons, 67% of black persons, and 56% of Asian persons received inpatient medical rehabilitation after hip or knee joint replacement. CONCLUSION: Disparity in outcomes appeared to be related to family structure and social support.