Effect of hydrostatic pressure on quaternary structure on the chaperone function of alpha-crystallin

High hydrostatic pressure-induced changes in bovine lens alpha-crystallin oligomers size and chaperone-like function were studied by a static light scattering. Under pressure 1.5 kbar, alpha-crystallin oligomers size is almost unaffected. Increase of the size was observed during several hours of incubation at 3 kbar. Such high-pressure effect on association has been previously revealed for detergent micelles, whereas the "typical" protein oligomers are known to dissociate under high pressure. Our results about pressure influence on alpha-crystallin association supports the previously proposed "protein micelle" model of the protein quaternary structure. Chaperone-like activity of alpha-crystallin is shown to increase after incubation at 3 kbar. After the end of the incubation this activity is slowly decreasing during several hours.     

Blind noise reduction for multisensory signals using ICA and subspace filtering, with application to EEG analysis

 In many applications of signal processing, especially in communications and biomedicine, preprocessing is necessary to remove noise from data recorded by multiple sensors. Typically, each sensor or electrode measures the noisy mixture of original source signals. In this paper a noise reduction technique using independent component analysis (ICA) and subspace filtering is presented. In this approach we apply subspace filtering not to the observed raw data but to a demixed version of these data obtained by ICA. Finite impulse response filters are employed whose vectors are parameters estimated based on signal subspace extraction. ICA allows us to filter independent components. After the noise is removed we reconstruct the enhanced independent components to obtain clean original signals; i.e., we project the data to sensor level. Simulations as well as real application results for EEG-signal noise elimination are included to show the validity and effectiveness of the proposed approach. Received: 6 November 2000 / Accepted in revised form: 12 November 2001     

Pathologic high shear stress induces apoptosis events in human platelets

Recently, it has been discovered that apoptosis of anucleate platelets can be induced by chemical agonists. Other studies demonstrated that mechanical forces (shear stresses) stimulate platelet activation and signaling in the absence of exogenous chemical stimuli. We analyzed whether shear stresses can trigger platelet apoptosis, a question that has not yet been studied. Using a cone-and-plate viscometer, we exposed human platelet-rich plasma to different shear stresses, ranging from physiologic arterial and arteriole levels (10-44 dyn/cm2) to pathologic high levels (117-388 dyn/cm2) occurring in stenotic vessels. We found that pathologic shear stresses induce not only platelet activation (P-selectin upregulation and GPIbalpha downregulation) but also trigger apoptosis events, including mitochondrial transmembrane potential depolarization, caspase 3 activation, phosphatidylserine exposure, and platelet shrinkage and fragmentation, whereas physiological shear stresses are not effective.This novel finding suggests that shear-induced platelet apoptosis can be mediated by mechanoreceptors, does not require nuclear participation, and may affect platelet clearance.     

Outlining folding nuclei in globular proteins

Our theoretical approach for prediction of folding/unfolding nuclei in three-dimensional protein structures is based on a search for free energy saddle points on networks of protein unfolding pathways. Under some approximations, this search is performed rapidly by dynamic programming and results in prediction of Phi values, which can be compared with those found experimentally. In this study, we optimize some details of the model (specifically, hydrogen atoms are taken into account in addition to heavy atoms), and compare the theoretically obtained and experimental Phi values (which characterize involvement of residues in folding nuclei) for all 17 proteins, where Phi values are now known for many residues. We show that the model provides good Phi value predictions for proteins whose structures have been determined by X-ray analysis (the average correlation coefficient is 0.65), with a more limited success for proteins whose structures have been determined by NMR techniques only (the average correlation coefficient is 0.34), and that the transition state free energies computed from the same model are in a good anticorrelation with logarithms of experimentally measured folding rates at mid-transition (the correlation coefficient is -0.73).     

Protein chip-based microarray profiling of oxidized low density lipoprotein-treated cells

Commercially available high-content Ab380 and extensively validated DLM26 homemade protein microarrays were used to profile the effects of the pro-atherogenic molecule, oxidized low density lipoprotein (OxLDL), on human aortic smooth muscle cells. Protein microarrays detected 298 proteins in cell lysates and 54 of these were differentially regulated. Microarray data were validated by immunoblotting for a selected set of up- and down-regulated proteins. The protein microarray data sets were compared with our recent cDNA microarray-based gene expression results in order to characterize the global effect of OxLDL on smooth muscle cell functions. A group of cell-cell interaction molecules was classified as up-regulated by OxLDL, whereas nucleic acid/protein biosynthesis, structural and humoral response proteins/genes were under-expressed in cells treated by OxLDL. These findings reveal the major pattern of OxLDL-induced effects on the human aortic smooth muscle cells functions and also demonstrate that protein chip-based microarrays could be a useful proteomic tool to profile disease-related states of muscle cells.     

Multiple Trp isoforms implicated in capacitative calcium entry are expressed in human pregnant myometrium and myometrial cells

Capacitative Ca2+ entry plays a role in thapsigargin- and oxytocin-mediated increases in intracellular free Ca2+ in human myometrium. Members of the Trp protein family have been implicated in capacitative Ca2+ entry in a number of tissues. Pregnant human myometrium and the human myometrial cell line PHM1-41 expressed mRNA for hTrp1, hTrp3, hTrp4, hTrp6, and hTrp7. A number of known splice variants of hTrp1 and hTrp4 were expressed in these cells. In addition, novel splice variants for hTrp1 and hTrp3 were discovered. hTrp1gamma1 and hTrp1gamma2 contain insertions between previously described exons 9 and 10 that would alter reading frame and produce Trp proteins truncated in the membrane spanning region if expressed. The hTrp3 variant introduces sequence between exons 8 and 9 that would insert 16 amino acids in the C-terminal region of the protein upstream of the calmodulin and inositol 1,4,5-triphosphate receptor interaction domain. hTrp1, hTrp3, and hTrp4 proteins were detected in both pregnant human myometrial and PHM1-41 membranes; a weak band consistent with hTrp6 expression was detected in pregnant human myometrium. These data are consistent with the presence of proteins that could form putative capacitative Ca2+ channels in human myometrium. Control of the activity of these channels may be important for the control of uterine contractile activity.     

Kv1.2 Channels Promote Nonlinear Spiking Motoneurons for Powering Up Locomotion

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