Tyrosine kinases activate store-mediated Ca2+ entry in human platelets through the reorganization of the actin cytoskeleton

Abstract

We have recently reported that store-mediated Ca# + entry in platelets is likely to be mediated by a reversible trafficking and coupling of the endoplasmic reticulum with the plasma membrane, a model termed ' secretion-like coupling '. In this model the actin cytoskeleton plays a key regulatory role. Since tyrosine kinases have been shown to be important for Ca# + entry in platelets and other cells, we have now investigated the possible involvement of tyrosine kinases in the secretion-like-coupling model. Treatment of platelets with thrombin or thapsigargin induced actin polymerization by a calcium-independent pathway. Methyl 2,5-dihydroxycinnamate, a tyrosine kinase inhibitor, prevented thrombin-or thapsigargin-induced actin polymerization. The effects of tyrosine kinases in store-mediated Ca# + entry

Phosphoinositides Are Required for Store-mediated Calcium Entry in Human Platelets

“…Therefore, LY294002 reduced actin polymerization induced by TG or thrombin at concentrations that inhibit both PI3-and PI4-kinases. Our observations are in agreement with our previous studies reporting that actin polymerization is required for the activation and maintenance of SMCE in human platelets (8,9). Treatment of platelets with LY294002 had no effect on basal levels of F-actin (data not shown) indicating that either treadmilling is very slow in human platelets or phosphoinositides are not important for the maintenance of the actin network in resting platelets.…”

“…LY294002 Inhibits Actin Polymerization in Platelets-The actin cytoskeleton has been shown to play a key role in the activation and maintenance of SMCE in platelets (8,9) and other cells (3,7), and phosphoinositides are required for actin polymerization (10,11). Hence we have now investigated the effect of different concentrations of LY294002 on actin filament formation in platelets to assess whether the involvement of phosphoinositides on SMCE activation could be in the reorganization of the actin filament network.…”

“…This involves a physical but reversible interaction between the ER and the PM that may require translocation of portions of the ER toward the PM and mechanical support provided by the actin cytoskeleton (3,4). In support of this hypothesis, small GTP-binding proteins, which modulate vesicular transport through the reorganization of the actin cytoskeleton and the actin cytoskeleton itself, have been suggested to be important for SMCE in different cell types (5-7) including platelets (8,9).…”

Sesamol induces apoptosis in human platelets via reactive oxygen species-mediated mitochondrial damage

“…The lysate was centrifuged at 16,000Â g for 5 min. The pellet thus obtained is the cytoskeleton-rich (Triton-insoluble) fraction, which was subjected to caspase activity and Western blotting [20].…”

Propensity of crocin to offset Vipera russelli venom induced oxidative stress mediated neutrophil apoptosis: a biochemical insight

“…Cell lysate was prepared according to the method of Rosado et al (2000). Briefly, venom treated (with/ without crocin for 30 min) and control cells were lysed with an equal volume of 29 Triton buffer (100 mM Tris-HCl, pH 7.2 containing 2 % TritonX-100, 2 mM EGTA, 100 lg/mL leupeptin, 2 mM PMSF, 10 mM benzamidine, 2 mM Na 3 VO 4 ) at 4°C for 30 min.…”