Our data show for the first time that UII-induced VSMCs proliferation and CREB activation requires a complex signalling pathway that involves on the one hand SOCE mediated by STIM1, Orai1, and TRPC1, and on the other hand EGFR, ERK, and CaMK activation.
Homocysteine, a sulphur-containing amino acid derived from methionine, has been presented as an independent risk factor for cardiovascular disorders, including atherosclerosis and thrombogenesis. The mechanisms underlying homocysteine-induced effects have been intensively investigated over the last two decades. Homocysteine can induce oxidative stress promoting oxidant injury to vascular and blood cells. Hyperhomocysteinemia often results in intracellular Ca2+ mobilization, endoplasmic reticulum (ER) stress, with the subsequent development of apoptotic events, chronic inflammation leading to endothelial dysfunction and remodeling of the extracellular matrix. Homocysteine has also been reported to induce modulation of gene expression through alteration of the methylation status. The effects of elevated concentrations of circulating homocysteine on the vascular wall, platelet function and coagulation factors promote the development of a pro-coagulant state. The pathophysiological significance of homocysteine in the development of vascular disorders through the induction of endothelial dysfunction and abnormal platelet activity and blood coagulation is discussed in this review.
Store-operated Ca 2+ entry (SOCE) is a major pathway for Ca 2+ influx in non-excitable cells.Recent studies favour a conformational coupling mechanism between the endoplasmic reticulum (ER) Ca 2+ sensor STIM1 and Ca 2+ permeable channels in the plasma membrane to explain SOCE. Previous studies have reported a role for the cytoskeleton modulating the activation of SOCE; therefore, here we have investigated whether the interaction between STIM1 and the Ca 2+ permeable channels is modulated by the actin or microtubular network.In . Thus, we demonstrate that the cytoskeleton plays an essential role in the regulation of SOCE through the modulation of the interaction between their main molecular components.
Different studies have reported that proteins involved in Ca(2+) entry are localized in discrete plasma membrane domains known as lipid rafts, which have been suggested to support store-operated Ca(2+) entry by facilitating STIM1 clustering in endoplasmic reticulum-plasma membrane junctions as well as the interaction of STIM1 with TRPC1. Here we report that treatment of HEK293 cells with thapsigargin (TG) results in the activation of Ca(2+) entry with two components, an early, La(3+)-sensitive, component and a late component that shows both La(3+)-sensitive and -insensitive constituents. Preincubation with methyl-beta-cyclodextrin (MbetaCD) prevented TG-induced activation of Ca(2+) entry but, in contrast, enhanced this process after its activation. Addition of MbetaCD after store depletion did not modify the La(3+)-sensitive store-operated divalent cation entry but increased La(3+)-insensitive non-capacitative Ca(2+) entry. Cell stimulation with TG results in a transient increase in Orai1 co-immunoprecipitation with STIM1, TRPC1 and TRPC6. TG-induced association of these proteins was significantly attenuated by preincubation for 30 min with MbetaCD, without altering surface expression of Orai1 or TRPCs. In contrast, the association of Orai1 with STIM1 or TRPC1 was unaffected when MbetaCD was added after store depletion with TG. Addition of MbetaCD to TG-treated cells promoted dissociation between Orai1 and TRPC6, as well as non-capacitative Ca(2+) entry. TRPC6 expression silencing indicates that MbetaCD-enhanced non-capacitative Ca(2+) entry was mediated by TRPC6. In conclusion, lipid raft domains are necessary for the activation but not the maintenance of SOCE probably due to the support of the formation of Ca(2+) signalling complexes involving Orai1, TRPCs and STIM1.
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