PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-12 (12)
 

Clipboard (0)
None
Journals
more »
Year of Publication
Document Types
1.  Regulation of KLF4 turnover reveals an unexpected tissue specific role of pVHL in tumorigenesis 
Molecular cell  2012;45(2):233-243.
SUMMARY
The transcription factor Krüppel-like factor 4 (KLF4) is an important regulator of cell fate decision, including cell cycle regulation, apoptosis, and stem cell renewal, and plays an ambivalent role in tumorigenesis as a tissue specific tumor suppressor or oncogene. Here we report that the Von Hippel-Lindau gene product, pVHL, physically interacts with KLF4 and regulates its rapid turnover observed in both differentiated and stem cells. We provide mechanistic insights into KLF4 degradation and show that pVHL depletion in colorectal cancer cells leads to cell cycle arrest concomitant with increased transcription of the KLF4-dependent p21 gene. Finally, immunohistochemical staining revealed elevated pVHL and reduced KLF4 levels in colon cancer tissues. We therefore propose that unexpectedly pVHL, via the degradation of KLF4, is a facilitating factor in colorectal tumorigenesis.
doi:10.1016/j.molcel.2011.11.031
PMCID: PMC3982234  PMID: 22284679
2.  CASE REPORT Spontaneous Forearm Compartment Syndrome in a Boy With Hemophilia A: A Therapeutic Dilemma 
Eplasty  2013;13:e16.
Objective: We present the case of a 14-year-old Factor VIII-deficient patient with no history of trauma, who developed acute spontaneous compartment syndrome of the volar forearm. We also suggest a treatment strategy. Methods: Fasciotomy with hematoma evacuation and ipsilateral carpal tunnel release was performed, and the wound was closed with vascular loops in “Jacob's ladder” fashion. Factor infusions were continued overnight. Results: The volar forearm compartment was successfully decompressed, and the patient's coagulopathy was managed with appropriate clotting factors. Conclusions: Hemophilic patients warrant special consideration and multispecialty care; with replenished coagulation factors and timely surgical decompression, they can expect satisfactory recovery of muscular and neurological function.
PMCID: PMC3601454  PMID: 23573336
3.  TcyR regulates L-cystine uptake via the TcyABC transporter in Streptococcus mutans 
Fems Microbiology Letters  2012;328(2):114-121.
Streptococcus mutans, a primary dental pathogen, has a remarkable capacity to scavenge nutrients from the oral biofilm for its survival. Cystine is an amino acid dimer formed by the oxidation of two cysteine residues that is required for optimal growth, whereas S. mutans modulates l-cystine uptake via two recently identified transporters designated TcyABC and TcyDEFGH, which have not been fully characterized. Using a non-polar tcyABC-deficient mutant (SmTcyABC), here we report that L-cystine uptake is drastically diminished in the mutant, whereas its ability to grow is severely impaired under l-cystine starvation conditions, relative to wild type. A substrate competition assay showed that l-cystine uptake by the TcyABC transporter was strongly inhibited by dl-cystathionine and l-djenkolic acid and moderately inhibited by S-methyl-l-cysteine and l-cysteine. Using gene expression analysis, we observed that the tcyABC operon was up-regulated under cystine starvation. TcyABC has been shown to be positively regulated by the LysR-type transcriptional regulator CysR. We identified another LysR-type transcriptional regulator that negatively regulates TcyABC with homology to the B. subtilis YtlI regulator, which we termed TcyR. Our study enhances the understanding of l-cystine uptake in S. mutans which allows survival and persistence of this pathogen in the oral biofilm.
doi:10.1111/j.1574-6968.2011.02492.x
PMCID: PMC3288405  PMID: 22212096
Cystine; cysteine; transport; TcyABC; Streptococcus mutans
4.  Phase I Clinical Trial of the CYP17 Inhibitor Abiraterone Acetate Demonstrating Clinical Activity in Patients With Castration-Resistant Prostate Cancer Who Received Prior Ketoconazole Therapy 
Journal of Clinical Oncology  2010;28(9):1481-1488.
Purpose
Abiraterone acetate is a prodrug of abiraterone, a selective inhibitor of CYP17, the enzyme catalyst for two essential steps in androgen biosynthesis. In castration-resistant prostate cancers (CRPCs), extragonadal androgen sources may sustain tumor growth despite a castrate environment. This phase I dose-escalation study of abiraterone acetate evaluated safety, pharmacokinetics, and effects on steroidogenesis and prostate-specific antigen (PSA) levels in men with CPRC with or without prior ketoconazole therapy.
Patients and Methods
Thirty-three men with chemotherapy-naïve progressive CRPC were enrolled. Nineteen patients (58%) had previously received ketoconazole for CRPC. Bone metastases were present in 70% of patients, and visceral involvement was present in 18%. Three patients (9%) had locally advanced disease without distant metastases. Fasted or fed cohorts received abiraterone acetate doses of 250, 500, 750, or 1,000 mg daily. Single-dose pharmacokinetic analyses were performed before continuous daily dosing.
Results
Adverse events were predominantly grade 1 or 2. No dose-limiting toxicities were observed. Hypertension (grade 3, 12%) and hypokalemia (grade 3, 6%; grade 4, 3%) were the most frequent serious toxicities and responded to medical management. Confirmed ≥ 50% PSA declines at week 12 were seen in 18 (55%) of 33 patients, including nine (47%) of 19 patients with prior ketoconazole therapy and nine (64%) of 14 patients without prior ketoconazole therapy. Substantial declines in circulating androgens and increases in mineralocorticoids were seen with all doses.
Conclusion
Abiraterone acetate was well tolerated and demonstrated activity in CRPC, including in patients previously treated with ketoconazole. Continued clinical study is warranted.
doi:10.1200/JCO.2009.24.1281
PMCID: PMC2849769  PMID: 20159824
5.  Cardiorespiratory Fitness and Attentional Control in the Aging Brain 
A growing body of literature provides evidence for the prophylactic influence of cardiorespiratory fitness on cognitive decline in older adults. This study examined the association between cardiorespiratory fitness and recruitment of the neural circuits involved in an attentional control task in a group of healthy older adults. Employing a version of the Stroop task, we examined whether higher levels of cardiorespiratory fitness were associated with an increase in activation in cortical regions responsible for imposing attentional control along with an up-regulation of activity in sensory brain regions that process task-relevant representations. Higher fitness levels were associated with better behavioral performance and an increase in the recruitment of prefrontal and parietal cortices in the most challenging condition, thus providing evidence that cardiorespiratory fitness is associated with an increase in the recruitment of the anterior processing regions. There was a top-down modulation of extrastriate visual areas that process both task-relevant and task-irrelevant attributes relative to the baseline. However, fitness was not associated with differential activation in the posterior processing regions, suggesting that fitness enhances attentional function by primarily influencing the neural circuitry of anterior cortical regions. This study provides novel evidence of a differential association of fitness with anterior and posterior brain regions, shedding further light onto the neural changes accompanying cardiorespiratory fitness.
doi:10.3389/fnhum.2010.00229
PMCID: PMC3024830  PMID: 21267428
cardiorespiratory fitness; Stroop task; cognitive and attentional control
7.  Deducing the transmembrane domain organization of presenilin-1 in γ-secretase by cysteine disulfide crosslinking† 
Biochemistry  2006;45(24):7598-7604.
γ-Secretase is a founding member of membrane-embedded aspartyl proteases that cleave substrates within transmembrane domains, and this enzyme is an important target for the development of therapeutics for Alzheimer’s disease. The structure of γ-secretase and its precise catalytic mechanism still remain largely unknown. γ-Secretase is a complex of four integral membrane proteins, with presenilin (PS) as the catalytic component. To gain structural and functional information about the 9-transmembrane domain (TMD) presenilin, we employed a cysteine mutagenesis/disulfide-crosslinking approach. Here we report that native Cys92 is close to both Cys410 and Cys419, strongly implying that TMD1 and TMD8 are adjacent to each other. This structural arrangement also suggests that TMD8 is distorted from an ideal helix. Importantly, binding of an active-site directed inhibitor, but not a docking-site directed inhibitor, reduces the ability of the native cysteine pairs of PS1 to crosslink upon oxidation. These findings suggest that the conserved cysteines of TMD1 and TMD8 contribute to or allosterically interact with the active site of γ-secretase.
doi:10.1021/bi060107k
PMCID: PMC2597485  PMID: 16768455
8.  Does Apolipoprotein E Genotype Influence the Risk of Ischemic Stroke, Intracerebral Hemorrhage, or Subarachnoid Hemorrhage? 
Background and Purpose
Apolipoprotein E genotype (APOE) is associated with cholesterol metabolism, ischemic heart disease, and cerebral amyloid angiopathy, and so may affect risk of both ischemic and hemorrhagic stroke.
Methods
We comprehensively sought and identified studies of the association of apoE with ischemic stroke (IS), intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH). We did meta-analyses to assess the evidence for an association between APOE and the various pathological types and subtypes of stroke, and assessed the effects of several methodological criteria.
Results
We analyzed data from 31 eligible studies (26 IS, 8 ICH, and 3 SAH) in 5961 cases and 17 965 controls. ∊4 allele-containing (∊4+) genotypes were significantly associated with IS (odds ratio [OR], 1.11; 95% CI, 1.01 to 1.22) and SAH (OR, 1.42; 95% CI, 1.01 to 1.99) and nonsignificantly with ICH (OR, 1.16; 95% CI, 0.93 to 1.44), whereas ∊2+ genotypes were associated with ICH (OR, 1.32; 95% CI, 1.01 to 1.74). Associations appeared stronger with ∊4+ genotypes for large artery compared with other IS subtypes and for Asian compared with white populations, and with ∊2+ genotypes for lobar compared with deep hemorrhages. However, we found no association between ∊4+ genotypes and IS when we analyzed only larger studies (>200 cases; OR, 0.99; 95% CI, 0.88 to 1.11) or studies without control selection bias (OR, 0.99; 95% CI, 0.85 to 1.17).
Conclusions
Publication and selection biases make existing studies of APOE and stroke unreliable. Further, very large, methodologically rigorous studies are needed.
doi:10.1161/01.STR.0000199065.12908.62
PMCID: PMC2577180  PMID: 16385096
apolipoproteins E; genetics; meta-analysis; stroke
9.  Positive influence of AP-2α transcription factor on cadherin gene expression and differentiation of the ocular surface 
The family of transcription factors Activating protein-2 (AP-2) are known to play important roles in numerous developmental events, including those associated with differentiation of stratified epithelia. However, to date, the influence of the AP-2 genes on endogenous gene expression in the stratified epithelia and how this affects differentiation has not been well defined. The following study examines the detailed expression of the AP-2α and AP-2β proteins in the stratified epithelia of the ocular surface, including that in the cornea and developing eyelids. The effect of altered levels of the AP-2α gene on ocular surface differentiation was also examined using a corneal epithelial cell line and AP-2α chimeric mice. Immunolocalization studies revealed that, while AP-2β was broadly expressed throughout all cell layers of the stratified corneal epithelium, AP-2α expression was confined to cell compartments more basally located. AP-2α was also highly expressed in the less differentiated cell layers of the eyelid epidermis. Overexpression of the AP-2α gene in the corneal cell line, SIRC, resulted in a dramatic change in cell phenotype including a clumping growth behavior that was distinct from the smooth monolayer of the parent cell line. Accompanying this change was an up-regulation in levels of the cell adhesion molecule, N-cadherin. Examination of the ocular surface of AP-2α chimeric mice, derived from a mixed population of AP-2α−/− and AP-2α+/+, revealed that a down-regulation in E-cadherin expression is correlated with location of the AP-2α−/− null cells. Together, these findings demonstrate that AP-2α participates in regulating differentiation of the ocular surface through induction in cadherin expression.
PMCID: PMC2517417  PMID: 12694203
ocular surface; cell adhesion; transcription factors; AP-2; cornea; eyelids; differentiation
10.  Mammalian Sir2 Homolog SIRT3 Regulates Global Mitochondrial Lysine Acetylation▿ †  
Molecular and Cellular Biology  2007;27(24):8807-8814.
Homologs of the Saccharomyces cerevisiae Sir2 protein, sirtuins, promote longevity in many organisms. Studies of the sirtuin SIRT3 have so far been limited to cell culture systems. Here, we investigate the localization and function of SIRT3 in vivo. We show that endogenous mouse SIRT3 is a soluble mitochondrial protein. To address the function and relevance of SIRT3 in the regulation of energy metabolism, we generated and phenotypically characterized SIRT3 knockout mice. SIRT3-deficient animals exhibit striking mitochondrial protein hyperacetylation, suggesting that SIRT3 is a major mitochondrial deacetylase. In contrast, no mitochondrial hyperacetylation was detectable in mice lacking the two other mitochondrial sirtuins, SIRT4 and SIRT5. Surprisingly, despite this biochemical phenotype, SIRT3-deficient mice are metabolically unremarkable under basal conditions and show normal adaptive thermogenesis, a process previously suggested to involve SIRT3. Overall, our results extend the recent finding of lysine acetylation of mitochondrial proteins and demonstrate that SIRT3 has evolved to control reversible lysine acetylation in this organelle.
doi:10.1128/MCB.01636-07
PMCID: PMC2169418  PMID: 17923681
11.  Simultaneous development of the Pediatric GERD Caregiver Impact Questionnaire (PGCIQ) in American English and American Spanish 
Background
The objective of this study was to develop simultaneously a new questionnaire, the Pediatric GERD Caregiver Impact Questionnaire (PGCIQ), in American English and American Spanish in order to elucidate the impact of caring for a child with GERD.
Methods
Two focus group discussions were conducted in American English and American Spanish to develop a relevant conceptual model. Focus group participants were the primary caregivers of children with GERD (newborn through 12 years of age). Participant responses were qualitatively analyzed to identify potential differences in caregiver perspectives by the caregiver's language, socio-economic status and demographic profile as well as the child's age and disease severity level. Items in the PGCIQ were generated simultaneously in English and Spanish by reviewing results of qualitative analysis from focus groups in each language. The PGCIQ was finalized in both languages after testing content validity and conducting an in-depth translatability assessment.
Results
Analysis of focus group comments resulted in the development of a first draft questionnaire consisting of 58 items in 10 domains. Content validity testing and an in-depth translatability assessment resulted in wording modification of 37 items, deletion of 14 items and the addition of a domain with five items. Feedback from the content validity testing interviews indicated that the instrument is conceptually relevant in both American English and American Spanish, clear, comprehensive and easy to complete within 10 minutes. The final version of the PGCIQ contains 49 items assessing ten domains. An optional module with nine items is available for investigative research purposes and for use only at baseline.
Conclusion
The PGCIQ was developed using simultaneous item generation, a process that allows for consideration of concept relevance in all stages of development and in all languages being developed. The PGCIQ is the first questionnaire to document the multidimensional impact of caring for an infant or young child with GERD. Linguistic adaptation of the PGCIQ in multiple languages is ongoing. A validation study of the PGCIQ is needed to examine its psychometric properties, further refine the items and develop an appropriate scoring model.
doi:10.1186/1477-7525-3-5
PMCID: PMC548517  PMID: 15651991
12.  Restricted Immunoglobulin Variable Region (Ig V) Gene Expression Accompanies Secondary Rearrangements of Light Chain Ig V Genes in Mouse Plasmacytomas 
The Journal of Experimental Medicine  1999;190(10):1405-1416.
The many binding studies of monoclonal immunoglobulin (Ig) produced by plasmacytomas have found no universally common binding properties, but instead, groups of plasmacytomas with specific antigen-binding activities to haptens such as phosphorylcholine, dextrans, fructofuranans, or dinitrophenyl. Subsequently, it was found that plasmacytomas with similar binding chain specificities not only expressed the same idiotype, but rearranged the same light (VL) and heavy (VH) variable region genes to express a characteristic monoclonal antibody. In this study, we have examined by enzyme-linked immunosorbent assay five antibodies secreted by silicone-induced mouse plasmacytomas using a broader panel of antigens including actin, myosin, tubulin, single-stranded DNA, and double-stranded DNA. We have determined the Ig heavy and light chain V gene usage in these same plasmacytomas at the DNA and RNA level. Our studies reveal: (a) antibodies secreted by plasmacytomas bind to different antigens in a manner similar to that observed for natural autoantibodies; (b) the expressed Ig heavy genes are restricted in V gene usage to the VH-J558 family; and (c) secondary rearrangements occur at the light chain level with at least three plasmacytomas expressing both κ and λ light chain genes. These results suggest that plasmacytomas use a restricted population of B cells that may still be undergoing rearrangement, thereby bypassing the allelic exclusion normally associated with expression of antibody genes.
PMCID: PMC2195694  PMID: 10562316
V(D)J rearrangement; plasmacytoma; allelic exclusion; polyreactivity; V gene usage

Results 1-12 (12)