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VGSC Activity (vgsc + activity)
Selected AbstractsEstrogen and non-genomic upregulation of voltage-gated Na+ channel activity in MDA-MB-231 human breast cancer cells: Role in adhesion,JOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2010Scott P. Fraser External (but not internal) application of ,-estradiol (E2) increased the current amplitude of voltage-gated Na+ channels (VGSCs) in MDA-MB-231 human breast cancer (BCa) cells. The G-protein activator GTP-,-S, by itself, also increased the VGSC current whilst the G-protein inhibitor GDP-,-S decreased the effect of E2. Expression of GPR30 (a G-protein-coupled estrogen receptor) in MDA-MB-231 cells was confirmed by PCR, Western blot and immunocytochemistry. Importantly, G-1, a specific agonist for GPR30, also increased the VGSC current amplitude in a dose-dependent manner. Transfection and siRNA-silencing of GPR30 expression resulted in corresponding changes in GPR30 protein expression but only internally, and the response to E2 was not affected. The protein kinase A inhibitor, PKI, abolished the effect of E2, whilst forskolin, an adenylate cyclase activator, by itself, increased VGSC activity. On the other hand, pre-incubation of the MDA-MB-231 cells with brefeldin A (a trans -Golgi protein trafficking inhibitor) had no effect on the E2-induced increase in VGSC amplitude, indicating that such trafficking (,externalisation') of VGSC was not involved. Finally, acute application of E2 decreased cell adhesion whilst the specific VGSC blocker tetrodotoxin increased it. Co-application of E2 and tetrodotoxin inhibited the effect of E2 on cell adhesion, suggesting that the effect of E2 was mainly through VGSC activity. Pre-treatment of the cells with PKI abolished the effect of E2 on adhesion, consistent with the proposed role of PKA. Potential implications of the E2-induced non-genomic upregulation of VGSC activity for BCa progression are discussed. J. Cell. Physiol. 224: 527,539, 2010. © 2010 Wiley-Liss, Inc. [source] Activity-dependent regulation of voltage-gated Na+ channel expression in Mat-LyLu rat prostate cancer cell lineTHE JOURNAL OF PHYSIOLOGY, Issue 2 2006William J. Brackenbury We have shown previously that voltage-gated Na+ channels (VGSCs) are up-regulated in human metastatic disease (prostate, breast and small-cell lung cancers), and that VGSC activity potentiates metastatic cell behaviours. However, the mechanism(s) regulating functional VGSC expression in cancer cells remains unknown. We investigated the possibility of activity-dependent (auto)regulation of VGSC functional expression in the strongly metastatic Mat-LyLu model of rat prostate cancer. Pretreatment with tetrodotoxin (TTX) for 24,72 h subsequently suppressed peak VGSC current density without affecting voltage dependence. The hypothesis was tested that the VGSC auto-regulation occurred via VGSC-mediated Na+ influx and subsequent activation of protein kinase A (PKA). Indeed, TTX pretreatment reduced the level of phosphorylated PKA, and the PKA inhibitor KT5720 decreased, whilst the adenylate cyclase activator forskolin and the Na+ ionophore monensin both increased the peak VGSC current density. TTX reduced the mRNA level of Nav1.7, predominant in these cells, and VGSC protein expression at the plasma membrane, although the total VGSC protein level remained unchanged. TTX pretreatment eliminated the VGSC-dependent component of the cells' migration in Transwell assays. We concluded that the VGSC activity in Mat-LyLu rat prostate cancer cells was up-regulated in steady-state via a positive feedback mechanism involving PKA, and this enhanced the cells' migratory potential. [source] Anatomical characterisation of voltage gated sodium channels in the mammalian cochlear nerve spiral gangliaCLINICAL OTOLARYNGOLOGY, Issue 6 2006A. Prasai Introduction., There is evidence that Voltage Gated Sodium Channels (VGSC) may represent novel therapeutic targets for treatment of certain types of tinnitus and hearing loss. It is also known that the different VGSC types vary in their affinity for differing VGSC blockers. Parallels have been drawn with certain types of tinnitus, chronic pain and epilepsy (1) These conditions are thought to arise from pathological VGSC activity (2) There has also been empirical interest in the use of VGSC blockers as tinnitolytics, with the best known of these being intravenous lignocaine. Aim., The aim of this study was first begin to characterise VGSCs in the mammalian cochlear nerve spiral ganglion. Method., After sacrifice, guinea pigs were perfused with heparin and then 2% paraformaldehyde. The bony matrix of the cochleae was decalcified in buffer containing EGTA (8%). Decalcified tissues were embedded; frozen and 20-micron cryosections were made through the cochleae. Immunocytochemistry was then carried out using antibodies that selectively bind to individual sodium channel ,-subunits. Sections were then analysed and photographed using either an epifluorescence or a confocal microscope. Results and Conclusions., Sodium channel type 1.6 and 1.7 were shown to be expressed in the cochlear nerve spiral ganglion. Further work is being carried out to see if there are changes in the expression of these VGSC after ototrauma. These findings may help us to target our therapy to treat certain types of tinnitus and hearing loss. References 1 Smith P.F., Darlington C.L. (2005) Drug treatments for subjective tinnitus: serendipitous discovery versus rational drug design. Curr. Opin. Investig. Drugs.6, 712,716 2 Taylor C.P., Meldrum B.S. (1995) Na+ channels as targets for neuroprotective drugs. Trends. Pharmacol. Sci. 16, 309,315 [source] | ||||||||||