Store-operated channels

G. Rocchitta, R. Migheli, M.P. Mura, G. Esposito, M.S. Desole, E. Miele, M. Miele, and P.A. Serra, Signalling pathways in the nitric oxide donor-induced dopamine release in the striatum of freely moving rats evidence that exogenous nitric oxide promotes Ca2+ entry through store-operated channels. Brain Res. 1023, 243-252 (2004). 

Sanders When you talk about store-operated channels, are you considering TRP channels as being part of this ... 

Kotlikoff Returning to the issue of receptor-operated or store-operated channels, one of the things I noticed in your traces was that your caffeine responses came back to baseline very smoothly. There was not the sustained elevation of [Ca2+] that you might predict. One of the things that is very different about voltage-clamped smooth muscle between a caffeine response and a phospholipase receptor-linked response is this additional current that is seen with the phospholipase receptor. I didn t see any functional evidence of a sustained response in your caffeine experiments. Have you voltage clamped these cells and looked to see whether there is any current there If not, do you think this is because the current is just too small to be able to measure ... 

McCarron No, although we only have indirect evidence for this. Our reasoning is that the tonic component is blocked by inhibitors of the voltage-dependent Ca2+ channel, and it is not blocked by the SKF96365 which blocks store-operated channels. 

TRPC4 may form part of a store-operated channel (SOC) complex... 

Ca2+ enters cells via a number of plasma membrane channels which belong to three families (Figure 11.2) (i) voltage-gated channels (ii) ligand-gated channels and (iii) capacitative, or store-operated channels (SOCs). 

CaSR may also influence the proliferative and apoptotic status of the cells indirectly via modulation of cell volume homeostasis. Indeed, stimulation of CaSR in human epithelial cells induces upregulation of volume-regulated anion channels (VRAC) via a G protein-mediated increase in intracellular cAMP (Shimizu, et al., 2000). Proliferation and apoptosis are associated with essential volume perturbations [e.g., (Lang, et al., 2000)] and VRAC, a key component of homeostatic volume regulation, has been directly implicated in proliferation (Chen, et al., 2002, Doroshenko, et al., 2001, Shen, et al., 2000, Wang, et al., 2002) and apoptosis (Lemonnier, et al., 2004, Okada, et al., 2001, Okada, et al., 2006, Shen, et al., 2002). Consequently, extracellular Ca2+ may affect carcinogenesis via the CaSR-VRAC-cell volume links. The Ca2+ -permeable store-operated channel (SOC) is directly and functionally coupled to VRAC in an androgen-dependent LNCaP human prostate cancer epithelial cell line (Lemonnier, et al., 2002), evidence for another, CaSR-unrelated, potential mechanism for extracellular Ca2+ involvement in proliferative and apoptotic events. 

Lemonnier, L., Prevarskaya, N., Shuba, Y., Vanden Abeele, F., Nilius, B., Mazurier, J. and Skryma, R., 2002, Ca2+ modulation of volume-regulated anion channels evidence for colocalization with store-operated channels. Faseb J 16, 222-4. 

Beech, D. J. 2005. TRPCl store-operated channel and more. PflugersArch 451, 53-60. 

Alfonso, A., Roman, Y., Vieytes, M.R., Ofuji, K., Satake, M., Yasumoto, T, and Botana, L.M. 2005. Azaspiracid-4 inhibits Ca21 entry by stored operated channels in human T lymphocytes. Biochem Pharmacol 69, 1627-1636. 

Small nuclear ribonucleoprotein particle Soil organic carbon store-operated channel Suppressors of cytokine signaling Superoxide dismutase CuZn-SOD enzyme (intracellular)... 

Store-operated channels are activated in response to depletion of the intracellular Ca2+ stores. The mechanism by which depletion of the internal stores is sensed by these channels is unknown. 

Alfonso, A. et al., Azaspiracid-4 inhibits Ca entry by stored operated channels in human T lympho-... 

In a similar model, AZA-4 was reported not to modify cytosolic calcium in resting human lymphocytes. However, AZA-4 inhibited the increase in cytosolic calcium levels induced by Tg in a dose-dependent manner but did not affect the Ca -release from internal stores induced by this drug. These effects were reversible and not regulated by cAMP pathway. AZA-4 appeared to be a novel inhibitor of plasma membrane Ca channels, affecting store-operated channels, showing an effect different from other AZA analogues.It was the author s opinion that the inability of AZA-4 and AZA-5 to increase Ca influx lowered their relative toxicity compared to AZA-1 and AZA-3. 

Attempts to compensate for impaired calcium signaling due to reduced endoplasmic reticulum Ca ATPase fimction, include enhanced calcium entry through L-type calcium channels and store-operated channels in vascular smooth muscle cells in SHR (Tabet et al., 2004 Fellner and Arendshorst, 2002). Impaired vascular... 

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