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The role of caveolins, signature proteins of caveolae, in arterial [Ca.sup.2+] regulation is unknown. We investigated modulation of [Ca.sup.2+] homeostasis by caveolin-1 and caveolin-3 using smooth muscle cells from rat cerebral resistance arteries. Membrane current and [Ca.sup.2+] transients were simultaneously measured with voltage-clamped single cells. Membrane depolarization triggered [Ca.sup.2+] current and increased intracellular [Ca.sup.2+] concentration ([[Ca.sup.2+]].sub.i]). After repolarization, elevated [[Ca.sup.2+]].sub.i] returned to the resting level. [Ca.sup.2+] removal rate was determined from the declining phase of the [Ca.sup.2+] transient. Application of caveolin-1 antibody or caveolin-1 scaffolding domain peptide, corresponding to amino acid residues 82-101 of caveolin-1, significantly slowed [Ca.sup.2+] removal rate at a measured [[Ca.sup.2+]].sub.i] of 250 nM, with little effect at a measured [[Ca.sup.2+]].sub.i] of 600 nM. Application of caveolin-3 antibody or caveolin-3 scaffolding domain peptide, corresponding to amino acid residues 55-74 of caveolin-3, also significantly slowed [Ca.sup.2+] removal rate at a measured [[Ca.sup.2+]].sub.i] of 250 nM, with little effect at a measured [[[Ca.sup.2+]].sub.i] of 600 nM. Likewise, application of calmodulin inhibitory peptide, autocamtide-2-related inhibitory peptide, and cyclosporine A, inhibitors for calmodulin, [Ca.sup.2+]/calmodulin-dependent protein kinase II, and calcineurin, also significantly inhibited [Ca.sup.2+] removal rate at a measured [[Ca.sup.2+]].sub.i] of 250 nM but not at 600 nM. Application of cyclopiazonic acid, a sarcoplasmic reticulum [Ca.sup.2+] ATPase inhibitor, also significantly inhibited [Ca.sup.2+] removal rate at a measured [[Ca.sup.2+]].sub.i] of 250 nM but not at 600 nM. Our results suggest that caveolin-1 and caveolin-3 are important in [Ca.sup.2+] removal of resistance artery smooth muscle cells. caveolin-1 scaffolding domain peptide; caveolin-3 scaffolding domain peptide; calmodulin; calcium/calmodulin-dependent protein kinase II; calcineurin doi:10.1152/ajpheart.00669.2006

White clover (Trifolium repens L.) is an important legume in grassland ecosystems. Its persistence in mixed grass-clover swards, however, is dependent on utilization of stored carbohydrates during overwintering and subsequent spring regrowth. Reserve carbohydrate is stored as starch in stolons. Our objective was to determine how activities of starch hydrolytic enzymes change during defoliation-induced starch mobilization in clover stolons. Starch degradation was induced by defoliating clonally propagated plants maintained in a controlled environment. Defoliation resulted in rapid, extensive starch remobilization from older stolon tissues, and prevented starch accumulation in young, developing stolon tissues. Amylase activities of stolon tissue were determined immediately, 1, 2, 4, 8, and 12 d post-defoliation. Total amylolytic activity decreased following defoliation. Of the starch hydrolytic enzyme activities determined, only the activity of [Alpha]-amylase increased as a consequence of defoliation (two-fold, with respect to the control). Β-amylase, which constituted the greatest proportion of total amylolytic activity, decreased two- to three-fold in stolons of defoliated plants, but increased six-fold in young stolon tissue, and almost two-fold in old stolon tissue. The increase in enzyme activity correlated with starch deposition in control plants. Starch phosphorylase activity also decreased as a result of defoliation, while activity of [Alpha]-glucosidase changed little following the defoliation treatment. Our results suggest starch degradation in Stolons (If white clover is regulated by [Alpha]-amylase activity., White clover is a perennial forage legume that grows under a wide range of climatic conditions. It plays an increasingly important role in managed grasslands due to its high nutritional [...]

In the human breast cancer cell line MCF-7, the nucleotides ATPγS and UTP, acting extracellularly through the purinergic receptor P2Y2, lead to elevated intracellular calcium levels and increased proliferation. ATPγS and UTP treatment of MCF-7 cells activated transcription of the immediate early gene c-fos, an important component in the response to proliferative stimulation. c-fos induction was enhanced by co-treatment with ATPγS and a variety of proliferative agents including growth factors, tumour promoters and stress. Stimulation with ATPγS or epidermal growth factor (EGF) led to extracellular signal-regulated kinase (ERK) activation and phosphorylation of the transcription factors CREB and Elk-1. Co-stimulation synergistically activated fos expression and notably led to increased levels of ERK, CREB and EGF receptor phosphorylation, as well as hyperphosphorylation of ternary complex factor. Nevertheless, the ERK pathway does not fully account for this synergy, since fos induction was differentially sensitive to the MEK inhibitor U0126, indicating that these two agonists signal differently to this immediate early gene. Thus, extracellular nucleotides co-operate with growth factors to activate genes linked to the proliferative response in MCF-7 cells through activation of specific purinergic receptors, which thereby represent important potential targets for arresting the neoplastic progression of breast cancer cells. [ABSTRACT FROM PUBLISHER]