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Ca2+ Pumps (ca2+ + pump)
Selected AbstractsChanges in the expression of plasma membrane calcium extrusion systems during the maturation of hippocampal neuronsHIPPOCAMPUS, Issue 1 2006Sertac N. Kip Abstract Spatial and temporal control of intracellular calcium signaling is essential for neuronal development and function. The termination of local Ca2+ signaling and the maintenance of basal Ca2+ levels require specific extrusion systems in the plasma membrane. In rat hippocampal neurons (HNs) developing in vitro, transcripts for all isoforms of the plasma membrane Ca2+ pump and the Na/Ca2+ exchanger, and the major nonphotoreceptor Na+/Ca2+,K+ exchangers (NCKX) were strongly upregulated during the second week in culture. Upregulation of plasma membrane calcium ATPases (PMCAs)1, 3, and 4 mRNA coincided with a splice shift from the ubiquitous b-type to the neuron-specific a-type with altered calmodulin regulation. Expression of all PMCA isoforms increased over 5-fold during the first 2 weeks. PMCA immunoreactivity was initially concentrated in the soma and growth cones of developing HNs. As the cells matured, PMCAs concentrated in the dendritic membrane and often colocalized with actin-rich dendritic spines in mature neurons. In the developing rat hippocampal CA1 region, immunohistochemistry confirmed the upregulation of all PMCAs and showed that by the end of the second postnatal week, PMCAs1, 2, and 3 were concentrated in the neuropil, with less intense staining of cell bodies in the pyramidal layer. PMCA4 staining was restricted to a few cells showing intense labeling of the cell periphery and neurites. These results establish that all major Ca2+ extrusion systems are strongly upregulated in HNs during the first 2 weeks of postnatal development. The overall increase in Ca2+ extrusion systems is accompanied by changes in the expression and cellular localization of different isoforms of the Ca2+ pumps and exchangers. The accumulation of PMCAs in dendrites and dendritic spines coincides with the functional maturation in these neurons, suggesting the importance of the proper spatial organization of Ca2+ extrusion systems for synaptic function and development. © 2005 Wiley-Liss, Inc. [source] Factors controlling the activity of the SERCA2a pump in the normal and failing heartBIOFACTORS, Issue 6 2009Ilse Vandecaetsbeek Abstract Heart failure is the leading cause of death in western countries and is often associated with impaired Ca2+ handling in the cardiomyocyte. In fact, cardiomyocyte relaxation and contraction are tightly controlled by the activity of the cardiac sarco(endo)plasmic reticulum (ER/SR) Ca2+ pump SERCA2a, pumping Ca2+ from the cytosol into the lumen of the ER/SR. This review addresses three important facets that control the SERCA2 activity in the heart. First, we focus on the alternative splicing of the SERCA2 messenger, which is strictly regulated in the developing heart. This splicing controls the formation of three SERCA2 splice variants with different enzymatic properties. Second, we will discuss the role and regulation of SERCA2a activity in the normal and failing heart. The two well-studied Ca2+ affinity modulators phospholamban and sarcolipin control the activity of SERCA2a within a narrow window. An aberrantly high or low Ca2+ affinity is often observed in and may even trigger cardiac failure. Correcting SERCA2a activity might therefore constitute a therapeutic approach to improve the contractility of the failing heart. Finally, we address the controversies and unanswered questions of other putative regulators of the cardiac Ca2+ pump, such as sarcalumenin, HRC, S100A1, Bcl-2, HAX-1, calreticulin, calnexin, ERp57, IRS-1, and ,2. © 2009 International Union of Biochemistry and Molecular Biology, Inc. [source] Effects of chlorpromazine on excitation,contraction coupling events in fast-twitch skeletal muscle fibres of the ratBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2004R Wagner Single mechanically skinned fibres from the rat extensor digitorum longus muscle, which allow access to intracellular compartments, were used to examine the effects of 0.5,100 ,M chlorpromazine hydrochloride (CPZ) on the major steps of the excitation,contraction (E,C) coupling to elucidate the involvement of skeletal muscle in the neuroleptic malignant syndrome (NMS). At 1 ,M, CPZ caused a 20,30% increase in the force response induced by t-system depolarisation and a marked increase in the rate of caffeine-induced SR Ca2+ release. At [CPZ]2.5 ,M, there was an initial increase followed by a marked decrease of the t-system depolarisation-induced force responses, while the potentiating effect on the caffeine-induced SR Ca2+ release remained. These effects were reversible. CPZ had no effect on the maximum Ca2+ -activated force, but caused reversible, concentration-dependent increases in the Ca2+ sensitivity of the contractile apparatus at [CPZ] 10 ,M, with a 50% predicted shift of 0.11 pCa (,log [Ca2+]) units at 82.3 ,M CPZ. CPZ did not alter the rate of SR-Ca2+ loading at 1 and 10 ,M, but reversibly reduced it by ,40% at 100 ,M by reducing the SR Ca2+ pump. Nevertheless, the SR Ca2+ content was greater when fibres became unresponsive to t-system-induced depolarisation in the presence than in the absence of 100 ,M CPZ. The results show that CPZ has concentration-dependent stimulatory and inhibitory effects on various steps of the E,C coupling, which can explain the involvement of skeletal muscle in NMS and reconcile previous divergent data on CPZ effects on muscle. British Journal of Pharmacology (2004) 141, 624,633. doi:10.1038/sj.bjp.0705655 [source] Inhibition of SERCA Ca2+ pumps by 2-aminoethoxydiphenyl borate (2-APB)FEBS JOURNAL, Issue 15 20022-APB reduces both Ca2+ binding, by interfering with the pathway leading to the Ca2+ -binding sites, phosphoryl transfer from ATP 2-Aminoethoxydiphenyl Borate (2-APB) has been extensively used recently as a membrane permeable modulator of inositol-1,4,5-trisphosphate-sensitive Ca2+ channels and store-operated Ca2+ entry. Here, we report that 2-APB is also an inhibitor of sarco/endoplasmic reticulum Ca2+ -ATPase (SERCA) Ca2+ pumps, and additionally increases ion leakage across the phospholipid bilayer. Therefore, we advise caution in the interpretation of results when used in Ca2+ signalling experiments. The inhibition of 2-APB onthe SERCA Ca2+ pumps is isoform-dependent, with SERCA 2B being more sensitive than SERCA 1A (IC50 values for inhibition being 325 and 725 µm, respectively, measured at pH 7.2). The Ca2+ -ATPase is also more potently inhibited at lower pH (IC50 = 70 µm for SERCA1A at pH 6). 2-APB decreases the affinity for Ca2+ binding to the ATPase by more than 20-fold, and also inhibits phosphoryl transfer from ATP (by 35%), without inhibiting nucleotide binding. Activity studies performed using mutant Ca2+ -ATPases show that Tyr837 is critical for the inhibition of activity by 2-APB. Molecular modeling studies of 2-APB binding to the Ca2+ ATPase identified two potential binding sites close to this residue, near or between transmembrane helices M3, M4, M5 and M7. The binding of 2-APB to these sites could influence the movement of the loop between M6 and M7 (L6-7), and reduce access of Ca2+ to their binding sites. [source] Changes in the expression of plasma membrane calcium extrusion systems during the maturation of hippocampal neuronsHIPPOCAMPUS, Issue 1 2006Sertac N. Kip Abstract Spatial and temporal control of intracellular calcium signaling is essential for neuronal development and function. The termination of local Ca2+ signaling and the maintenance of basal Ca2+ levels require specific extrusion systems in the plasma membrane. In rat hippocampal neurons (HNs) developing in vitro, transcripts for all isoforms of the plasma membrane Ca2+ pump and the Na/Ca2+ exchanger, and the major nonphotoreceptor Na+/Ca2+,K+ exchangers (NCKX) were strongly upregulated during the second week in culture. Upregulation of plasma membrane calcium ATPases (PMCAs)1, 3, and 4 mRNA coincided with a splice shift from the ubiquitous b-type to the neuron-specific a-type with altered calmodulin regulation. Expression of all PMCA isoforms increased over 5-fold during the first 2 weeks. PMCA immunoreactivity was initially concentrated in the soma and growth cones of developing HNs. As the cells matured, PMCAs concentrated in the dendritic membrane and often colocalized with actin-rich dendritic spines in mature neurons. In the developing rat hippocampal CA1 region, immunohistochemistry confirmed the upregulation of all PMCAs and showed that by the end of the second postnatal week, PMCAs1, 2, and 3 were concentrated in the neuropil, with less intense staining of cell bodies in the pyramidal layer. PMCA4 staining was restricted to a few cells showing intense labeling of the cell periphery and neurites. These results establish that all major Ca2+ extrusion systems are strongly upregulated in HNs during the first 2 weeks of postnatal development. The overall increase in Ca2+ extrusion systems is accompanied by changes in the expression and cellular localization of different isoforms of the Ca2+ pumps and exchangers. The accumulation of PMCAs in dendrites and dendritic spines coincides with the functional maturation in these neurons, suggesting the importance of the proper spatial organization of Ca2+ extrusion systems for synaptic function and development. © 2005 Wiley-Liss, Inc. [source] Upregulation of P-cadherin expression in the lesional skin of pemphigus, Hailey-Hailey disease and Darier's diseaseJOURNAL OF CUTANEOUS PATHOLOGY, Issue 6 2001Megumi Hakuno Background: Autoimmune blistering diseases, pemphigus vulgaris (PV) and pemphigus foliaceus (PF), are known to be caused by binding of autoantibodies to the desmosomal cadherins, desmoglein 3 and desmoglein 1, respectively. Recently, mutations in the genes coding Ca2+ pumps leads to inherited blistering diseases, Hailey-Hailey disease (HHD) and Darier's disease (DD). Cadherins are a family of Ca2+ -dependent cell adhesion molecules and P-cadherin is one of the major cadherins expressed in the epidermis. Although detailed mechanisms of acantholysis of these blistering diseases have not been fully clarified, abnormal expression of cadherins caused by altered Ca2+ concentration due to the binding of autoantibodies to cell surface or by mutations in Ca2+ pumps is suggested to be involved in mechanisms of acantholysis of these atuoimmune and inherited blistering diseases. The purpose of the present study was to determine whether altered P-cadherin expression is present in these diseases. Method: Distribution patterns of P-cadherin in skin specimens from patients with PV (n=2), PF (n=2), HHD (n=4) and DD (n=3), were examined with confocal laser scanning microscopy using two anti-P-cadherin antibodies, 6A9 and NCC-CAD-299. Results: In normal control skin, P-cadherin expression was restricted to the basal layer. In contrast, positive immunostaining of P-cadherin was observed not only in the basal cells, but also in the suprabasal cells in lesional skin of all the acantholytic diseases. Conclusions: The present results clearly demonstrated that upregulation of P-cadherin expression occurs in the acantholysis in all the four blistering diseases PV, PF, HHD and DD. Upregulation of P-cadherin may be involved in the pathomechanism of both the autoimmune blistering diseases and the inherited blistering diseases. [source] Nuclear pore disassembly from endoplasmic reticulum membranes promotes Ca2+ signalling competencyTHE JOURNAL OF PHYSIOLOGY, Issue 12 2008Michael J. Boulware The functionality of the endoplasmic reticulum (ER) as a Ca2+ storage organelle is supported by families of Ca2+ pumps, buffers and channels that regulate Ca2+ fluxes between the ER lumen and cytosol. Although many studies have identified heterogeneities in Ca2+ fluxes throughout the ER, the question of how differential functionality of Ca2+ channels is regulated within proximal regions of the same organelle is unresolved. Here, we studied the in vivo dynamics of an ER subdomain known as annulate lamellae (AL), a cytoplasmic nucleoporin-containing organelle widely used in vitro to study the mechanics of nuclear envelope breakdown. We show that nuclear pore complexes (NPCs) within AL suppress local Ca2+ signalling activity, an inhibitory influence relieved by heterogeneous dissociation of nucleoporins to yield NPC-denuded ER domains competent at Ca2+ signalling. Consequently, we propose a novel generalized role for AL , reversible attenuation of resident protein activity , such that regulated AL (dis)assembly via a kinase/phosphatase cycle allows cells to support rapid gain/loss-of-function transitions in cellular physiology. [source] | |||||||||||||