Unique regulatory properties of the type 2a Ca2+ channel beta subunit caused by palmitoylation

Beta subunits of voltage-gated Ca2+ channels are encoded in four genes and display additional molecular diversity because of alternative splicing. At the functional level, all forms are very similar except for beta2a, which differs in that it does not support prepulse facilitation of alpha1C Ca2+ channels, inhibits voltage-induced inactivation of neuronal alpha1E Ca2+ channels, and is more effective in blocking inhibition of alpha1E channels by G protein-coupled receptors. We show that the distinguishing properties of beta2a, rather than interaction with a distinct site of alpha1, are because of the recently described palmitoylation of cysteines in positions three and four, which also occurs in the Xenopus oocyte. Essentially, all of the distinguishing features of beta2a were lost in a mutant that could not be palmitoylated [beta2a(Cys3,4Ser)]. Because protein palmitoylation is a dynamic process, these findings point to the possibility that regulation of palmitoylation may contribute to activity-dependent neuronal and synaptic plasticity. Evidence is presented that there may exist as many as three beta2 splice variants differing only in their N-termini.     

Results of surgical resection in patients over the age of 70 years with non small-cell lung cancer

Calcium release from the sarcoplasmic reticulum (SR) depending on depolarization of the transverse tubular membrane (TTM) caused by rapid ionic replacement was measured in skeletal muscle triadic vesicles using a stopped-flow apparatus and Fura-2, a membrane-impermeable Ca2+ indicator. Calcium release was triggered by an increase in the magnitude of depolarization. This Ca2+ release was inhibited by ruthenium red, digoxin and dantrolene, and enhanced by caffeine. Thus, Ca2+ release was found to occur through the SR Ca2+ release channel via TTM depolarization and to be able to cause skeletal muscle contraction. Calcium release curves could be divided into two phases. In contrast to other previous studies, in the fast phase the amount of released Ca2+ increased with an increase in the magnitude of depolarization but the Ca2+ release rate did not; on the other hand, in the slow phase the Ca2+ release rate increased but the amount of Ca2+ did not. Furthermore, the Ca2+ release rate was controlled by the luminal Ca2+ concentration of the SR only in the fast phase. These independent dual kinetics of Ca2+ release were explained by the calsequestrin regulation model.     

Voltage-controlled gating in a large conductance Ca2+-sensitive K+channel (hslo)

Large conductance calcium- and voltage-sensitive K+ (MaxiK) channels share properties of voltage- and ligand-gated ion channels. In voltage-gated channels, membrane depolarization promotes the displacement of charged residues contained in the voltage sensor (S4 region) inducing gating currents and pore opening. In MaxiK channels, both voltage and micromolar internal Ca2+ favor pore opening. We demonstrate the presence of voltage sensor rearrangements with voltage (gating currents) whose movement and associated pore opening is triggered by voltage and facilitated by micromolar internal Ca2+ concentration. In contrast to other voltage-gated channels, in MaxiK channels there is charge movement at potentials where the pore is open and the total charge per channel is 4-5 elementary charges.     

Supervisory run-to-run control of polysilicon gate etch using insitu ellipsometry

Polysilicon gate etch is a critical manufacturing step in the manufacturing of MOS devices because it determines the tolerance limits on MOS circuit performance. The etch used in the current study suffers from machine aging, which causes processing results to drift with time. Performing the etch for the same time with fixed process setpoints (recipe) for all wafers would produce unsatisfactory results. Thus, an in situ ellipsometer was employed with a new run-to-run supervisory controller, termed predictor corrector control (PCC), to eliminate the impact of machine and process drift. A novel modeling technique was used to predict uniformity from the ellipsometry data collected at a single site on the wafer. Predictive models are employed by the PCC supervisory controller to generate optimal settings (recipe) for every wafer which will achieve a target mean etch rate, while maintaining a spatially uniform etch. A 200 wafer experiment was conducted to demonstrate the benefits of process control. Implementation of PCC resulted in a 36% decrease in standard deviation from target for the mean etch rate. In addition, the data indicates that controlling etch rate may improve the control and uniformity of the line width change     

Looking for residues involved in the muscle acylphosphatase catalytic mechanism and structural stabilization: role of Asn41, Thr42, and Thr46

Asn41, Thr42, and Thr46 are invariant residues in both muscle and erythrocyte acylphosphatases isolated so far. Horse muscle acylphosphatase solution structure suggests their close spatial relationship to Arg23, the main substrate binding site. The catalytic and structural role of such residues, as well as their influence on muscle acylphosphatase stability, was investigated by preparing several gene mutants (Thr42Ala, Thr46Ala, Asn41Ala, Asn41Ser, and Asn41Gln) by oligonucleotide-directed mutagenesis. The mutated genes were cloned and expressed in Escherichia coli, and the mutant enzymes were purified by affinity chromatography and investigated as compared to the wild-type enzyme. The specific activity and substrate affinity of Thr42 and Thr46 mutants were not significantly affected. On the contrary, Asn41 mutants showed a residual negligible activity (about 0.05-0.15% as compared to wild-type enzyme), though maintaining an unchanged binding capability of both substrate and inorganic phosphate, an enzyme competitive inhibitor. According to the 1H nuclear magnetic resonance spectroscopy and circular dichroism results, all mutants elicited well-constrained native-like secondary and tertiary structures. Thermodynamic parameters, as calculated from circular dichroism data, demonstrated a significantly decreased stability of the Thr42 mutant under increasing temperatures and urea concentrations. The reported results strongly support a direct participation of Asn41 to the enzyme catalytic mechanism, indicating that Asn41 mutants may well represent a useful tool for the investigation of the enzyme physiological function by the negative dominant approach.     

A 10.7-MHz self-calibrated switched-capacitor-based multibit second-order bandpass /spl Sigma//spl Delta/ modulator with on-chip switched buffer

A second-order multibit bandpass /spl Sigma//spl Delta/ modulator (BP/spl Sigma//spl Delta/M) used for the digitizing of AM/FM radio broadcasting signals at a 10.7-MHz IF is presented. The BP/spl Sigma//spl Delta/M is realized with switched-capacitor (SC) techniques and operates with a sampling frequency of 37.05 MHz. The input impulse current, required by the SC input branch, is minimized by the use of a switched buffer without deteriorating the overall system performance. The accuracy of the in-band noise shaping is ensured with two self-calibrating control systems. In a 0.18-/spl mu/m CMOS technology, the device die size is 1 mm/sup 2/ and the power consumption is 88 mW. In production, the BP/spl Sigma//spl Delta/M features at least 78-dB dynamic range and 72-dB peak SNR within a 200-kHz bandwidth (FM bandwidth). The intermodulation (IMD) is -65 dBc for two tones at -11 dBFS. The robustness of the aforementioned performance is demonstrated by the fact that it has been realized with the BP/spl Sigma//spl Delta/M embedded in the noisy on-chip environment of a complete mixed-signal FM receiver.     

Stable isotope labeling with amino acids in cell culture based mass spectrometry approach to detect transient protein interactions using substrate trapping

The analysis of protein interactors in protein complexes can yield important insight into protein function and signal transduction. Thus, a reliable approach to distinguish true interactors from nonspecific interacting proteins is of utmost importance for accurate data interpretation. Although stringent purification methods are critical, challenges still remain in the selection of criteria that will permit the objective differentiation of true members of the protein complex from nonspecific background proteins. To address these challenges, we have developed a quantitative proteomic strategy combining stable isotope labeling with amino acids in cell culture (SILAC), affinity substrate trapping, and gel electrophoresis followed by liquid chromatography-tandem mass spectrometry (geLC-MS/MS) protein quantitation. ATP hydrolysis-deficient vacuolar protein sorting-associated protein 4B (Vps4B) was used as the "bait" protein which served as a substrate trap since its lack of ATP hydrolysis enzymatic activity allows the stabilization of its transiently associated interacting proteins. A significant advantage of our approach is the use of our new in-house-developed software program for SILAC-based mass spectrometry quantitation, which further facilitates the differentiation between the bait protein, endogenous bait-interacting proteins, and nonspecific binding proteins based on their protein ratios. The strategy presented herein is applicable to the analysis of other protein complexes whose compositions are dependent upon the ATP hydrolysis activity of the bait protein used in affinity purification studies.     

Meat intake, 'mate' drinking and renal cell cancer in Uruguay: a case-control study

In the period January 1988-December 1995, a case-control study of diet and renal cell carcinoma (RCC) risk involving 121 cases and 243 hospitalized controls was carried out in Montevideo, Uruguay. After adjusting for major covariates, red meat intake was associated with a 3.4 increase in risk for the highest category of intake, with a significant dose-response pattern. Also, barbecued meat, protein and heterocyclic amine intakes were associated with significant increases in risk of RCC. The consumption of the beverage known as 'mate' (a ocal tea derived from the herb Ilex paraguariensis) was associated with an increased risk of 3.0 for heavy drinkers.     

Enzyme activities and metabolites along the kynurenine pathway in mice with Harding-Passey melanoma

The effects of cyclophosphamide were studied 2, 5 and 9 days after terminating a two-week every-second-day intraperitoneal medication in young, male rats. The cytostatic effect was assessed by counting white blood cells (WBC) in arterial blood. WBC counts were reduced by 72% of control values at 2 days and regained normal values at 9 days after an overshooting leucocytosis at 5 days. Compared to control animals, the treated rats had significantly reduced body weights, metaphyseal bending strength and longitudinal growth of the femur at all time intervals observed. The torsional strength of the femur diaphysis and the strength of wounded skin were not affected at 2 days, but significantly reduced at 5 and 9 days. The tensile strength of intact skin was not found to be affected by the drug. From the 5th to the 9th day after ending medication, the curves for control and treated animals were assuming parallel slopes regarding metaphyseal bone strength, longitudinal bone growth and tensile strength of wounds. This may indicate reversion of the drug effects approximately one week after terminating medication.