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Plasma membrane Ca2+-ATPase (PMCA) by extruding Ca2+ outside the cell, actively participates in the regulation of intracellular Ca2+ concentration. Acting as Ca2+/H+ counter-transporter, PMCA transports large quantities of protons which may affect organellar pH homeostasis. PMCA exists in four isoforms (PMCA1-4) but only PMCA2 and PMCA3, due to their unique localization and features, perform more specialized function. Using differentiated PC12 cells we assessed the role of PMCA2 and PMCA3 in the regulation of intracellular pH in steady-state conditions and during Ca2+ overload evoked by 59 mM KCl. We observed that manipulation in PMCA expression elevated pHmito and pHcyto but only in PMCA2-downregulated cells higher mitochondrial pH gradient (ΔpH) was found in steady-state conditions. Our data also demonstrated that PMCA2 or PMCA3 knock-down delayed Ca2+ clearance and partially attenuated cellular acidification during KCl-stimulated Ca2+ influx. Because SERCA and NCX modulated cellular pH response in neglectable manner, and all conditions used to inhibit PMCA prevented KCl-induced pH drop, we considered PMCA2 and PMCA3 as mainly responsible for transport of protons to intracellular milieu. In steady-state conditions, higher TMRE uptake in PMCA2-knockdown line was driven by plasma membrane potential (Ψp). Nonetheless, mitochondrial membrane potential (Ψm) in this line was dissipated during Ca2+ overload. Cyclosporin and bongkrekic acid prevented Ψm loss suggesting the involvement of Ca2+-driven opening of mitochondrial permeability transition pore as putative underlying mechanism. The findings presented here demonstrate a crucial role of PMCA2 and PMCA3 in regulation of cellular pH and indicate PMCA membrane composition important for preservation of electrochemical gradient.

Angiotensin II (AngII), the main peptide of the renin‑angiotensin system (RAS), is involved in the proliferation of different types of cells, normal and pathological as well. The protein tyrosine kinases (PTKs) play an important role in the growth, differentiation and apoptosis of cells. AngII action depends on the hormonal milieu of the cell, and on sex steroid influence. Angiotensin 1‑7 (Ang1‑7), metabolite of AngII, shows opposite action to AngII in cells. The present study aimed to examine the influence of 17β‑estradiol and testosterone on AngII and Ang1‑7 action on PTK activity in androgen‑independent humane prostate cancer cell line DU145. Cell cultures of human prostate cancer DU145 cells were used as a source of PTKs. Cultures were exposed to different concentrations of AngII (5x10‑11 to 5x10‑9 M). The incubation with hormones lasted 15 min to limit the genomic effects of steroids. In the phosphorylation reaction, we used γ32P‑ATP as a donor of phosphate and a synthetic peptide, Poly(Glu, Tyr) (4:1), as a substrate. The specific activities of PTKs were defined as pmol of 32P incorporated into 1 mg of exogenous Poly(Glu, Tyr) per minute (pmol/mg/min). Our findings suggest that testosterone and 17β‑estradiol may change the effects of angiotensins in a rapid non‑genomic way, probably via membrane‑located receptors. The most significant change was caused by testosterone, whose effect was most significant on changes caused by Ang1‑7. AngII‑induced changes in phosphorylation appeared to be insensitive to the presence of testosterone, but were modified by 17β‑estradiol.

Microsomal glutathione-S-transferase 1 (Mgst1) plays a specific role in protection of cells against oxidative stress. In this study, we assayed the effect of Mgst1 downregulation on cells behavior using differentiated PC12 line, a widely accepted neuronal model system. We have developed stable transfected cells with downregulated Mgst1 (PC12_M), which were differentiated with 1 mM dibutyryl-cAMP (db-cAMP). Mgst1 reduction induced necrosis, decreased ATP amount, and increased thiobarbituric acid reacting substances (TBARS) content. However, in PC12_M cell population, we detected more intensive neuritogenesis than that in mock-transfected cells. Interestingly, total glutathione as well as GSH level were significantly higher than those in control PC12 line. Real-time PCR and Western blot analyses showed elevated expression of enzymes involved in glutathione metabolism-a rate-limiting γ-glutamylcysteine ligase and glutathione reductase. The present study shows for the first time that under stress conditions induced by Mgst1 downregulation, a rescue pathway can be activated and thereby enables differentiated PC12 cells to survive. Since Mgst1expression was reported to decline with age, our results could represent a putative adaptive process during aging. It could also be an early mechanism protecting neuronal cells against some neurodegenerative insults.

A close link between Ca2+, ATP level, and neurogenesis is apparent; however, the molecular mechanisms of this relationship have not been completely elucidated. Transient elevations of cytosolic Ca2+ may boost ATP synthesis, but ATP is also consumed by ion pumps to maintain a low Ca2+ in cytosol. In differentiation process plasma membrane Ca2+ ATPase (PMCA) is considered as one of the major players for Ca2+ homeostasis. From four PMCA isoforms, the fastest PMCA2 and PMCA3 are expressed predominantly in excitable cells. In the present study we assessed whether PMCA isoform composition may affect energy balance in differentiating PC12 cells. We found that PMCA2-downregulated cells showed higher basal O2 consumption, lower NAD(P)H level, and increased activity of ETC. These changes associated with higher [Ca2+]c resulted in elevated ATP level. Since PMCA2-reduced cells demonstrated greatest sensitivity to ETC inhibition, we suppose that the main source of energy for PMCA isoforms 1, 3, and 4 was oxidative phosphorylation. Contrary, cells with unchanged PMCA2 expression exhibited prevalence of glycolysis in ATP generation. Our results with PMCA2- or PMCA3-downregulated lines provide an evidence of a novel role of PMCA isoforms in regulation of bioenergetic pathways, and mitochondrial activity and maintenance of ATP level during PC12 cells differentiation.

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The synthesis of low-molecular-weight poly(acry1amide)s (M, = 500 -1000) is described. Metal-activated and non-activated polymerization in aqueous solution was investigated employing hydrogen peroxide as initiator. Among four transition metal salts considered, Cu2+ cations proved to be the most efficient in decomposing H202 molecules and were used as activator. The experiments were run at three reaction temperatures (60, 80 and 95 "C), at three H,O, levels (4, 5 and 6 wt.-Vo on monomer), and at four Cu2+ levels (900, 600, 300 and 0 ppm by weight of metal on monomer). Thus, ist was possible to prepare acrylamide oligomers with monomer conversions exceeding 95%, and with M, values covering the narrow range indicated above. Within these low limits a molecular weight control is impossible, even with inclusion of the differentiated

Alpha-synuclein (aSN) is a membrane-associated and intrinsically disordered protein, well-known for pathological aggregation in neurodegeneration. The physiological function of aSN however is disputed. Pull-down experiments have pointed to plasma membrane Ca2+-ATPase (PMCA) as a potential interaction partner. From proximity ligation assays we find here that aSN and PMCA colocalize at neuronal synapses, and that calcium expulsion is activated by aSN and PMCA. From PMCA activity studies we show that soluble, monomeric aSN activates PMCA at par with calmodulin, yet independent of the autoinhibitory domain of PMCA, but highly dependent on acidic phospholipids and the membrane-anchoring N-terminus of aSN. On the PMCA molecule, the interaction site is mapped to the acidic lipid-binding site, located within a PMCA-specific linker region connecting the cytosolic A domain and transmembrane segment 3. Our studies point towards a physiological role of monomeric aSN as a stimulator of calcium clearance in neurons through activation of PMCA