Structure-Based Development of Isoform-Selective Inhibitors of Casein Kinase 1ε vs Casein Kinase 1δ

Specific inhibition of a single kinase isoform is a challenging task due to the highly conserved nature of ATP-binding sites. Casein kinase 1 (CK1) δ and ε share 97% sequence identity in their catalytic domains. From a comparison of the X-ray crystal structures of CK1δ and CK1ε, we developed a potent and highly CK1ε-isoform-selective inhibitor (SR-4133). The X-ray co-crystal structure of the CK1δ-SR-4133 complex reveals that the electrostatic surface between the naphthyl unit of SR-4133 and CK1δ is mismatched, destabilizing the interaction of SR-4133 with CK1δ. Conversely, the hydrophobic surface area resulting from the Asp-Phe-Gly motif (DFG)-out conformation of CK1ε stabilizes the binding of SR-4133 in the ATP-binding pocket of CK1ε, leading to the selective inhibition of CK1ε. The potent CK1ε-selective agents display nanomolar growth inhibition of bladder cancer cells and inhibit the phosphorylation of 4E-BP1 in T24 cells, which is a direct downstream effector of CK1ε.

Dabrafenib and Trametinib Therapy for Advanced Anaplastic Thyroid Cancer - Real-World Outcomes From UK Centres

AIMS

Anaplastic thyroid cancer (ATC) is a rare but aggressive form of thyroid cancer with a median survival of 4 months. Recent advances in molecular profiling have shown that up to half of ATCs harbour the BRAF-V600E mutation. The aim of this study was to provide real-world data and experience on the use of combination therapy dabrafenib and trametinib in patients with BRAF-V600E-mutated advanced ATC.

MATERIALS AND METHODS

We retrospectively evaluated patients with confirmed BRAF-V600E-mutated ATC, defined as patients with locally advanced or metastatic ATC with no locoregional, radical treatment options. Outcomes measured were overall survival, progression-free survival, response rate, discontinuation rate, dose reduction rate and toxicity data.

RESULTS

Seventeen patients were evaluated and the mean age was 68 years. Ten patients died by the time of censoring. The median duration of follow-up was 12 months (3-43 months). The estimated median overall survival was 6.9 months (95% confidence interval 2.46 months - upper confidence interval not reached) and the median progression-free survival was 4.7 months (95% confidence interval 1.4-7.8 months). Dose interruptions and/or reductions were common, but none of the patients had to permanently discontinue treatment because of toxicities. Severe toxicities (grades 3 and 4) were uncommon.

CONCLUSIONS

This study supports the indication of dabrafenib and trametinib in BRAF-V600E-mutated ATC as an effective and well-tolerated treatment in an historically difficult to treat cancer.

Quality assurance of radiotherapy in the ongoing EORTC 1420 "Best of" trial for early stage oropharyngeal, supraglottic and hypopharyngeal carcinoma: results of the benchmark case procedure

INTRODUCTION

The current phase III EORTC 1420 Best-of trial (NCT02984410) compares the swallowing function after transoral surgery versus intensity modulated radiotherapy (RT) in patients with early-stage carcinoma of the oropharynx, supraglottis and hypopharynx. We report the analysis of the Benchmark Case (BC) procedures before patient recruitment with special attention to dysphagia/aspiration related structures (DARS).

MATERIALS AND METHODS

Submitted RT volumes and plans from participating centers were analyzed and compared against the gold-standard expert delineations and dose distributions. Descriptive analysis of protocol deviations was conducted. Mean Sorensen-Dice similarity index (mDSI) and Hausdorff distance (mHD) were applied to evaluate the inter-observer variability (IOV).

RESULTS

65% (23/35) of the institutions needed more than one submission to achieve Quality assurance (RTQA) clearance. OAR volume delineations were the cause for rejection in 53% (40/76) of cases. IOV could be improved in 5 out of 12 OARs by more than 10 mm after resubmission (mHD). Despite this, final IOV for critical OARs in delineation remained significant among DARS by choosing an aleatory threshold of 0.7 (mDSI) and 15 mm (mHD).

CONCLUSIONS

This is to our knowledge the largest BC analysis among Head and neck RTQA programs performed in the framework of a prospective trial. Benchmarking identified non-common OARs and target delineations errors as the main source of deviations and IOV could be reduced in a significant number of cases after this process. Due to the substantial resources involved with benchmarking, future benchmark analyses should assess fully the impact on patients' clinical outcome.

Targeting Casein Kinase 1 Delta Sensitizes Pancreatic and Bladder Cancer Cells to Gemcitabine Treatment by Upregulating Deoxycytidine Kinase

Although gemcitabine is the cornerstone of care for pancreatic ductal adenocarcinoma (PDA), patients lack durable responses and relapse is inevitable. While the underlying mechanisms leading to gemcitabine resistance are likely to be multifactorial, there is a strong association between activating gemcitabine metabolism pathways and clinical outcome. This study evaluated casein kinase 1 delta (CK1δ) as a potential therapeutic target for PDA and bladder cancer, in which CK1δ is frequently overexpressed. We assessed the antitumor effects of genetically silencing or pharmacologically inhibiting CK1δ using our in-house CK1δ small-molecule inhibitor SR-3029, either alone or in combination with gemcitabine, on the proliferation and survival of pancreatic and bladder cancer cell lines and orthotopic mouse models. Genetic studies confirmed that silencing CK1δ or treatment with SR-3029 induced a significant upregulation of deoxycytidine kinase (dCK), a rate-limiting enzyme in gemcitabine metabolite activation. The combination of SR-3029 with gemcitabine induced synergistic antiproliferative activity and enhanced apoptosis in both pancreatic and bladder cancer cells. Furthermore, in an orthotopic pancreatic tumor model, we observed improved efficacy with combination treatment concomitant with increased dCK expression. This study demonstrates that CK1δ plays a role in gemcitabine metabolism, and that the combination of CK1δ inhibition with gemcitabine holds promise as a future therapeutic option for metastatic PDA as well as other cancers with upregulated CK1δ expression.

Development of dual casein kinase 1δ/1ε (CK1δ/ε) inhibitors for treatment of breast cancer

Casein kinase 1δ/ε have been identified as promising therapeutic target for oncology application, including breast and brain cancer. Here, we described our continued efforts in optimization of a lead series of purine scaffold inhibitors that led to identification of two new CK1δ/ε inhibitors 17 and 28 displaying low nanomolar values in antiproliferative assays against the human MDA-MB-231 triple negative breast cancer cell line and have physical, in vitro and in vivo pharmacokinetic properties suitable for use in proof of principle animal xenograft studies against human cancers.

In Silico HTS and Structure Based Optimization of Indazole-Derived ULK1 Inhibitors

We present the outcome of an in silico high throughput screen (HTS) and optimization of a small molecule Unc-51-Like Kinase 1 (ULK1) inhibitor hit, SR-17398, with an indazole core. Docking studies guided design efforts that led to inhibitors with increased activity vs ULK1 (IC₅₀ < 50 nM). The most advanced molecules in this inhibitor series (3a and 3g) hold promise for further development into selective ULK1 molecular probes to interrogate the biology of ULK1 and to assess whether selectively targeting autophagy is an effective anticancer strategy.

Discovery of 2-arylquinazoline derivatives as a new class of ASK1 inhibitors

The development of a new series of apoptosis signal-regulating kinase 1 (ASK1) inhibitors is described. Starting from purine, pyrimidine and quinazoline scaffolds identified by high throughput screening, we used tools of structure-based drug design to develop a series of potent kinase inhibitors, including 2-arylquinazoline derivatives 12 and 23, with submicromolar inhibitory activities against ASK1. Kinetic analysis demonstrated that the 2-arylquinazoline scaffold ASK1 inhibitors described herein are ATP competitive.

Outpatient clinic numbers: a review of standards and current practice

This article explores current recommendations for the safe and efficient running of outpatient clinics, why non-adherence exists, the consequences of non-adherence, and what can be done to improve standards. It promotes adherence to recommendations by both clinical and managerial staff.

Impact of Immunoglobulin Therapy in Intestinal Transplant Recipients With Posttransplantation Hypogammaglobulinemia

BACKGROUND

Severe hypogammaglobulinemia (HGG) (IgG <400 mg/dL) following intestinal transplantation is common. Although IgG replacement therapy is commonly used, clinical outcomes associated with increasing IgG levels to >400 mg/dL are not well described.

METHODS

Kaplan-Meier analysis was performed to estimate survival, the log-rank test to compare survival distributions between groups, and the Fisher exact test to determine the association between HGG and rejection.

RESULTS

A total of 23 intestinal transplant (IT) recipients with a median age of 2.3 years (range, 0.7-41 years) at the time of HGG diagnosis were included. The types of transplants were liver-small bowel (73.9%), liver-small bowel-kidney (8.7%), and small bowel only (17.4%). The 3-year survival after the diagnosis of HGG was 50.2% (95% confidence interval [CI] = 28.2%-68.7%). There was no difference in survival (P = .67) when patients were dichotomized based upon IgG level at last follow-up (IgG ≥400 mg/dL, n = 14; and IgG <400 mg/dL, n = 9). There was no also evidence of an association between survival and: total dose (P = .58), frequency (P = .11), and number of IgG doses administered (P = .8). There was no difference in survival between patients receiving (n = 12) or not receiving (n = 11) cytomegalovirus hyperimmunoglobulin (P = .10).

CONCLUSIONS

Improved survival rates were not found in our IT recipients with severe HGG with immunoglobulin therapy to IgG levels of ≥400 mg/dL, even when cytomegalovirus hyperimmunoglobulin was administered.

Therapeutic targeting of casein kinase 1δ in breast cancer

Identification of specific drivers of human cancer is required to instruct the development of targeted therapeutics. We demonstrate that CSNK1D is amplified and/or overexpressed in human breast tumors and that casein kinase 1δ (CK1δ) is a vulnerability of human breast cancer subtypes overexpressing this kinase. Specifically, selective knockdown of CK1δ, or treatment with a highly selective and potent CK1δ inhibitor, triggers apoptosis of CK1δ-expressing breast tumor cells ex vivo, tumor regression in orthotopic models of triple-negative breast cancer, including patient-derived xenografts, and tumor growth inhibition in human epidermal growth factor receptor 2-positive (HER2(+)) breast cancer models. We also show that Wnt/β-catenin signaling is a hallmark of human tumors overexpressing CK1δ, that disabling CK1δ blocks nuclear accumulation of β-catenin and T cell factor transcriptional activity, and that constitutively active β-catenin overrides the effects of inhibition or silencing of CK1δ. Thus, CK1δ inhibition represents a promising strategy for targeted treatment in human breast cancer with Wnt/β-catenin involvement.

Development of an HTS-Compatible Assay for the Discovery of Ulk1 Inhibitors

A rapidly accumulating body of work suggests the autophagy pathway is an attractive therapeutic target for neurodegenerative diseases and cancer. To validate autophagy as an anticancer strategy and to assess if systemic inhibition of the pathway will have deleterious effects on normal tissues and physiology, highly selective autophagy inhibitors are needed. While several inducers and inhibitors of autophagy are known, all are nonspecific and none target the enzymes that execute the pathway. A central upstream regulator of the autophagy pathway is the serine/threonine kinase Ulk1 (UNC-51-like kinase-1). Selective molecular probes that function as Ulk1-specific inhibitors are needed to improve our understanding of the autophagy pathway. To identify inhibitors of Ulk1 kinase activity, we developed an HTS-compatible, homogeneous biochemical assay using AlphaScreen technology. This novel assay design uses purified stress-activated Ulk1 and monitors phosphorylation of its full-length native substrate, Atg13. This assay was optimized and validated in a 384-well format by screening the Sigma LOPAC library. Here we report that the Ulk1 AlphaScreen assay is robust and reproducible, with a Z' factor value of 0.83 ± 0.02 and a signal to background ratio of 20 ± 1.2. Thus, this assay can be used to screen large chemical libraries to discover novel inhibitors of Ulk1.

A single-dose, randomized, double-blind, placebo-controlled trial of sublingual asenapine for acute agitation

OBJECTIVE

To assess sublingual asenapine for acute agitation.

METHOD

Agitated adults 18-65 years (any diagnosis) presenting for treatment in an emergency department and found to have a score of ≥14 on the Positive and Negative Syndrome Scale-Excited Component (PANSS-EC) were randomized to receive either a single dose of a sublingual 10 mg tablet of asenapine or placebo. Primary outcome measure was change in the PANSS-EC score from baseline to 2 h after medication or placebo administration. Secondary outcomes included the percentage of responders with a ≥ 40% reduction from baseline on the PANSS-EC score at 2 h.

RESULTS

A total of 120 subjects were randomized, 60 each to sublingual asenapine or placebo. Mean (SE) baseline PANSS-EC scores for the asenapine-treated and placebo-treated subjects were 19.4 ± 0.66 and 20.1 ± 0.61, respectively. Mean PANSS-EC scores at endpoint (LOCF) was 7.4 ± 0.65 for the asenapine-treated subjects and 14.7 ± 0.98 for the placebo-treated subjects. Change in PANSS-EC score at 2 h was statistically significantly greater for the asenapine-treated subjects compared with the placebo-treated subjects. NNT for response vs. placebo was 3 (95% CI 2-4).

CONCLUSION

Sublingual asenapine was efficacious in the treatment of agitation with an effect size comparable to that observed in prior studies of intramuscular antipsychotics.

Synthesis and biological evaluation of urea derivatives as highly potent and selective rho kinase inhibitors

RhoA and its downstream effector ROCK mediate stress fiber formation and cell contraction through their effects on the phosphorylation of myosin light chain (MLC). Inhibition of the RhoA/ROCK pathway has proven to be a promising strategy for several indications such as cardiovascular disease, glaucoma, and inflammatory disease. In 2010, our group reported urea-based ROCK inhibitors as potential antiglaucoma agents. These compounds showed potent IC50 values in enzymatic and cell-based assays and significant intraocular pressure (IOP)-lowering effects in rats (∼7 mmHg). (22) To develop more advanced ROCK inhibitors targeting various potential applications (such as myocardial infarction, erectile dysfunction, multiple sclerosis, etc.) in addition to glaucoma, a thorough SAR for this urea-based scaffold was studied. The detailed optimization process, counter-screening, and in vitro and in vivo DMPK studies are discussed. Potent and selective ROCK inhibitors with various in vivo pharmacokinetic properties were discovered.

Amino acid derived quinazolines as Rock/PKA inhibitors

SAR and lead optimization studies for Rock inhibitors based on amino acid-derived quinazolines are described. Studies demonstrated that these amino acid derived quinazolinones were mainly pan-Rock (I & II) inhibitors. While selectivity against other kinases could be achieved, selectivity for most of these compounds against PKA was not achieved. This is distinct from Rock inhibitors based on non-amino acid derived quinazolinones, where high selectivity against PKA could be obtained.(22) The inhibitors presented here in some cases possessed sub-nanomolar inhibition of Rock, nanomolar potency in ppMLC cell based assays, low to fair cytochrome P-450 inhibition, and good human microsomal stability.

SU-E-T-210: Surviving a Visit by the Radiological Physics Center

PURPOSE

To demonstrate an objective approach to determining if a negative report from the Radiological Physics Center (RPC) of greater than 10% error is valid or has clinical significance.

METHODS

The discrepancy involved the clinical activity (mgRaEq) of Cs-137 sources, some manufactured by 3M and some by Amersham. Measurements were made in the proprietary RPC Well Counter calibrated by the MD Anderson ADCL and our Well Counter (CNMC, Model 44D) calibrated by the same laboratory as well as the University of Wisconsin ADCL. In addition, we possess an Amersham Cs-137 Check Source that had been calibrated by the UW-ADCL in 2002. All clinical sources were checked in both Well Counters on the first visit. One clinical source and the Check Source were measured in a second visit that occurred 51 days later.

RESULTS

On the initial RPC visit, 9 of 25 sources had a minimum of an 8% discrepancy between the RPC and the Institution, with a maximum of 11%. Contributing errors included using the incorrect straw position by us, an unexplained 2.3% error in the RPC data identified 73 days post-visit, a 2% variation in Chamber Factors for our Well Counter from the two ADCL's. When we use the 2004 value of Air Kerma Strength for the Check Source to determine a Calibration Factor of the Well Counter, all sources were within 0.5% of their decayed value established in 2002.

CONCLUSIONS

This work emphasizes the value of having simple Constancy Check systems in a Quality Assurance program as 'Accuracy' has error bars. The disagreement in calibration data between the ADCL Laboratories, which was at the 2% maximum quoted in their Calibration Reports, is a reminder that there is uncertainty in measurements. Constancy Checks allow one to sort out discrepancies and to answer challenges to the validity of your program.

Incidence, risk factors, and outcomes associated with cytomegalovirus disease in small bowel transplant recipients

Despite improved prophylaxis, monitoring, and more efficient immunosuppression, CMV infection remains a common opportunistic infection in transplant recipients. We assessed the incidence of CMV disease in pediatric SBT recipients, the timing of CMV disease after transplantation, and its impact on patient outcome. The medical records of 98 SBT recipients were reviewed. We performed descriptive analysis, regression analysis, and Kaplan-Meier curves to determine the time-to-event after transplantation. Fifty-three percent patients were male and 47% female, with a mean age of 38.3 months. Thirty-five percent of patients received prophylactic VGC, 55% GCV, 10% a combination of GCV/VGC, and 99% CMV immunoglobulins. A total of 24.5% recipients were CMV D+/R- (CMV serostatus donor positive/recipient negative). Seven (c. 7%) patients developed CMV disease. CMV disease was associated with 2.5 times (0.52-12.1; p = 0.25) higher rate of CMV mismatch and 11.1 times (1.3-95.9; p = 0.03) higher risk of death. CMV prophylaxis increased time-to-death (p = 0.074). Time-to-CMV disease was shorter in patients with enteritis (p < 0.0001), and CMV disease was associated with shorter time-to-death after transplantation (p = 0.001). CMV disease in SBT recipients was associated with an 11-fold mortality increase and a fourfold faster time-to-death. Time-to-death was significantly shorter with CMV enteritis.

The strain-specific dynamics of Escherichia coli O157:H7 faecal shedding in cattle post inoculation

This study reports analysis of faecal shedding dynamics in cattle for three Escherichia coli O157:H7 (ECO157) strains (S1, S2 and S3) of different genotype and ecological history, using experimental inoculation data. The three strains were compared for their shedding frequency and level of ECO157 in faeces. A multistate Markov chain model was used to compare shedding patterns of S1 and S2. Strains S1 and S2 were detected seven to eight times more often and at 10(4) larger levels than strain S3. Strains S1 and S2 had similar frequencies and levels of shedding. However, the total time spent in the shedding state during colonization was on average four times longer for S1 (15 days) compared to S2 (4 days). These results indicate that an ECO157 strain effect on the frequency, level, pattern and the duration of faecal shedding may need to be considered in control of ECO157 in the cattle reservoir.

Staphylococcus aureus infections after liver transplantation

BACKGROUND

More data on the risk factors and outcomes after Staphylococcus aureus infections in liver transplantation are needed.

METHODS

Liver recipients with S. aureus infections (cases) were retrospectively identified and compared to gender-, age-, and transplant type-matched (1:2) non-S. aureus-infected controls. Risk factors associated with S. aureus infections were identified by conditional logistic regression analysis.

RESULTS

We evaluated 51 patients (median age 52 years). First S. aureus infections developed at a median time of 29 days after transplantation, with 52.94% of them in the first month; 88.24% were nosocomial, 41.18% were polymicrobial, and 47.06% were caused by methicillin-resistant S. aureus (MRSA). Surgical site infections represented 58.82% and bacteremia 23.53%. By univariate analysis, patients with S. aureus infections were intubated more frequently (odds ratio [OR] 26.92, 95% confidence interval [CI] 3.23-3,504.15, p = 0.0006), had a central line (OR 11.69, 95% CI 1.42-95.9, p = 0.02), or recent surgery (OR 26.92, 95% CI 3.23-3,504.15, p = 0.0006) compared with controls. By multivariate analysis, subjects who underwent surgery within 2 weeks prior to infection had a 26.9 times higher risk of developing S. aureus infection (95% CI 3.23-3,504.15, p = 0.0006); these results were adjusted for matched criteria. S. aureus infections did not affect graft or patient survival, but the study was not powered for such outcomes.

CONCLUSION

Only recent surgical procedure was found to be a significant independent risk factor for S. aureus infections after liver transplantation.

A stress response pathway regulates DNA damage through β2-adrenoreceptors and β-arrestin-1

The human mind and body respond to stress, a state of perceived threat to homeostasis, by activating the sympathetic nervous system and secreting the catecholamines adrenaline and noradrenaline in the 'fight-or-flight' response. The stress response is generally transient because its accompanying effects (for example, immunosuppression, growth inhibition and enhanced catabolism) can be harmful in the long term. When chronic, the stress response can be associated with disease symptoms such as peptic ulcers or cardiovascular disorders, and epidemiological studies strongly indicate that chronic stress leads to DNA damage. This stress-induced DNA damage may promote ageing, tumorigenesis, neuropsychiatric conditions and miscarriages. However, the mechanisms by which these DNA-damage events occur in response to stress are unknown. The stress hormone adrenaline stimulates β(2)-adrenoreceptors that are expressed throughout the body, including in germline cells and zygotic embryos. Activated β(2)-adrenoreceptors promote Gs-protein-dependent activation of protein kinase A (PKA), followed by the recruitment of β-arrestins, which desensitize G-protein signalling and function as signal transducers in their own right. Here we elucidate a molecular mechanism by which β-adrenergic catecholamines, acting through both Gs-PKA and β-arrestin-mediated signalling pathways, trigger DNA damage and suppress p53 levels respectively, thus synergistically leading to the accumulation of DNA damage. In mice and in human cell lines, β-arrestin-1 (ARRB1), activated via β(2)-adrenoreceptors, facilitates AKT-mediated activation of MDM2 and also promotes MDM2 binding to, and degradation of, p53, by acting as a molecular scaffold. Catecholamine-induced DNA damage is abrogated in Arrb1-knockout (Arrb1(-/-)) mice, which show preserved p53 levels in both the thymus, an organ that responds prominently to acute or chronic stress, and in the testes, in which paternal stress may affect the offspring's genome. Our results highlight the emerging role of ARRB1 as an E3-ligase adaptor in the nucleus, and reveal how DNA damage may accumulate in response to chronic stress.

Discovery of Potent and Selective Urea-Based ROCK Inhibitors and Their Effects on Intraocular Pressure in Rats

A series of urea-based Rho kinase (ROCK) inhibitors were designed and evaluated. The discovered compounds had excellent enzyme and cellular potency, high kinase selectivity, high aqueous solubility, good porcine corneal penetration, and appropriate DMPK profiles for topical applications as antiglaucoma therapeutics.

Characterisation of a fatty acid and retinol binding protein orthologue from the hookworm Ancylostoma ceylanicum

Hookworms, bloodfeeding intestinal nematodes, infect nearly one billion people in resource limited countries and are a leading cause of anaemia and malnutrition. Like other nematodes, hookworms lack the capacity to synthesise essential fatty acids de novo and therefore must acquire those from exogenous sources. The cDNA corresponding to a putative Ancylostoma ceylanicum fatty acid and retinol binding protein-1 (AceFAR-1) was amplified from adult hookworm mRNA. Studies using quantitative reverse transcriptase real-time PCR demonstrate that AceFAR-1 transcripts are most abundant in the earliest developmental stages of the parasite, and greater in females than males. Using in vitro assays, the recombinant AceFAR-1 (rAceFAR-1) was shown to bind individual fatty acids with equilibrium dissociation constants in the low micromolar range. The pattern of fatty acid uptake by live adult worms cultured ex vivo was similar to the in vitro binding profile of rAceFAR-1, raising the possibility that the native protein may be involved in acquisition of fatty acids by A. ceylanicum. Animals vaccinated orally with rAceFAR-1 and the mucosal adjuvant cholera toxin exhibited a statistically significant (40-47%) reduction in intestinal worm burden compared with controls immunized with antigen or adjuvant alone. Together, these data suggest a potential role for AceFAR-1 in hookworm biology, making it a potentially valuable target for drug and vaccine development.

Nucleoplasmic calcium is required for cell proliferation

Ca(2+) signals regulate cell proliferation, but the spatial and temporal specificity of these signals is unknown. Here we use selective buffers of nucleoplasmic or cytoplasmic Ca(2+) to determine that cell proliferation depends upon Ca(2+) signals within the nucleus rather than in the cytoplasm. Nuclear Ca(2+) signals stimulate cell growth rather than inhibit apoptosis and specifically permit cells to advance through early prophase. Selective buffering of nuclear but not cytoplasmic Ca(2+) signals also impairs growth of tumors in vivo. These findings reveal a major physiological and potential pathophysiological role for nucleoplasmic Ca(2+) signals and suggest that this information can be used to design novel therapeutic strategies to regulate conditions of abnormal cell growth.

Functional Coupling of Chromogranin with the Inositol 1,4,5-Trisphosphate Receptor Shapes Calcium Signaling

Chromogranins A and B are high capacity, low affinity calcium (Ca(2+)) storage proteins that bind to the inositol 1,4,5-trisphosphate-gated receptor (InsP(3) R). Although most commonly associated with secretory granules of neuroendocrine cells, chromogranins have also been found in the lumen of the endoplasmic reticulum (ER) of many cell types. To investigate the functional consequences of the interaction between the InsP(3) R and the chromogranins, we disrupted the interaction between the two proteins by adding a chromogranin fragment, which competed with chromogranin for its binding site on the InsP(3)R. Responses were monitored at the single channel level and in intact cells. When using InsP(3) R type I incorporated into planar lipid bilayers and activated by cytoplasmic InsP(3) and luminal chromogranin, the addition of the fragment reversed the enhancing effect of chromogranin. Moreover, the expression of the fragment in the ER of neuronally differentiated PC12 cells attenuated agonist-induced intracellular Ca(2+) signaling. These results show that the InsP(3)R/chromogranin interaction amplifies Ca(2+) release from the ER and that chromogranin is an essential component of this intracellular channel complex.

Cofilin produces newly polymerized actin filaments that are preferred for dendritic nucleation by the Arp2/3 complex

One of the earliest events in the process of cell motility is the massive generation of free actin barbed ends, which elongate to form filaments adjacent to the plasma membrane at the tip of the leading edge. Both cofilin and Arp2/3 complex have been proposed to contribute to barbed end formation during cell motility. Attempts to assess the functions of cofilin and Arp 2/3 complex in vivo indicate that both cofilin and Arp2/3 complex contribute to actin polymerization: cofilin by severing and Arp2/3 by nucleating and branching. In order to determine if the activities of cofilin and Arp2/3 complex interact, we employed a light microscope-based assay to visualize actin polymerization directly in the presence of both proteins. The results indicate that cofilin generates barbed ends to increase the mass of freshly polymerized F-actin but does not directly affect the activity of Arp2/3 complex. However, while ADP, ADP-Pi, and newly polymerized ATP-filaments are all capable of supporting Arp2/3-mediated branching, newly polymerized F-actin supports most of the Arp2/3-induced branch formation. The results suggest that, in vivo, cofilin contributes to barbed end formation by inducing the initial increase in the number of barbed ends leading to increased ATP-F-actin, which in turn supports higher levels of dendritic nucleation by active Arp2/3 complex.

Safety and efficacy of repeat transradial access for cardiac catheterization procedures

To determine the safety and efficacy of repeat transradial cardiac catheterization, 1,362 consecutive transradial procedures were examined. Repeat transradial procedures were identified (group I, n = 73) and compared with index procedures (group II, n = 1,289). Baseline patient characteristics, procedure success rates (100% vs. 97.9%; P = NS), complication rates (0% vs. 0.08%; P = NS), and procedure times (23.9 +/- 27.3 min vs. 18.2 +/- 14.7 min; P = NS) were similar between groups. This study suggests that repeat transradial catheterization procedures can be performed safely and successfully in appropriately selected patients.