The Plasma Membrane Ca2+ Pump PMCA4b Regulates Melanoma Cell Migration through Remodeling of the Actin Cytoskeleton.

We demonstrated that the plasma membrane Ca2+ ATPase PMCA4b inhibits migration and metastatic activity of BRAF mutant melanoma cells. Actin dynamics are essential for cells to move, invade and metastasize, therefore, we hypothesized that PMCA4b affected cell migration through remodeling of the actin cytoskeleton. We found that expression of PMCA4b in A375 BRAF mutant melanoma cells induced a profound change in cell shape, cell culture morphology, and displayed a polarized migratory character. Along with these changes the cells became more rounded with increased cell-cell connections, lamellipodia and stress fiber formation. Silencing PMCA4b in MCF-7 breast cancer cells had a similar effect, resulting in a dramatic loss of stress fibers. In addition, the PMCA4b expressing A375 cells maintained front-to-rear Ca2+ concentration gradient with the actin severing protein cofilin localizing to the lamellipodia, and preserved the integrity of the actin cytoskeleton from a destructive Ca2+ overload. We showed that both PMCA4b activity and trafficking were essential for the observed morphology and motility changes. In conclusion, our data suggest that PMCA4b plays a critical role in adopting front-to-rear polarity in a normally spindle-shaped cell type through F-actin rearrangement resulting in a less aggressive melanoma cell phenotype.

Molecular Diversity of Plasma Membrane Ca2+ Transporting ATPases: Their Function Under Normal and Pathological Conditions.

Plasma membrane Ca2+ transport ATPases (PMCA1-4, ATP2B1-4) are responsible for removing excess Ca2+ from the cell in order to keep the cytosolic Ca2+ ion concentration at the low level essential for normal cell function. While these pumps take care of cellular Ca2+ homeostasis they also change the duration and amplitude of the Ca2+ signal and can create Ca2+ gradients across the cell. This is accomplished by generating more than twenty PMCA variants each having the character - fast or slow response, long or short memory, distinct interaction partners and localization signals - that meets the specific needs of the particular cell-type in which they are expressed. It has become apparent that these pumps are essential to normal tissue development and their malfunctioning can be linked to different pathological conditions such as certain types of neurodegenerative and heart diseases, hearing loss and cancer. In this chapter we summarize the complexity of PMCA regulation and function under normal and pathological conditions with particular attention to recent developments of the field.

The demise of preimplantation genetic testing for aneuploidy (PGT-A) in Hungary and its effect on patient care.

Preimplantation genetic testing for aneuploidy (PGT-A) is a suitable technique to identify euploid embryos, which have the highest potential to implant, thus increase the chance of a healthy live birth. The main indications of PGT-A are advanced maternal age, repeated implantation failure, repeated miscarriages and severe male infertility. Several studies have already proven that testing embryos for genetic abnormalities in the above cases results in higher implantation rate and reduced number of pregnancy loss. In spite of these - due to a legislative change in Hungary in 2015 - PGT-A was reclassified as an experimental procedure and its use became banned throughout the country. For this reason, after 4 years of successful practice, Hungarian patients were not able to participate in IVF procedure combined with PGT-A anymore. In this retrospective analysis, efficacy of PGT-A-based embryo selection was evaluated and was compared to the conventional morphology-based selection (MBS) in patients with advanced maternal age, between 2013 and 2017 at our private fertility clinic. PGT-A was performed with array comparative genomic hybridization. We found that implantation rate was significantly higher (43.62% vs. 27.88%; p = 0.0208) and miscarriage rate was significantly lower (17.07% vs. 37.93%; p = 0.0492) in the PGT-A group compared to the MBS group from 2013 to 2015. These outcomes were achieved with a significantly lower number of transferred embryos in the PGT-A group (1.25 vs. 1.58; p = 0.0003). In 2016-2017, the number of transferred embryos were significantly reduced in the MBS group as well (1.14 vs. 1.58; p < 0.0001). However, outcomes of the IVF treatments did not change significantly compared to the previous two years (2013-2015). Our results imply that PGT-A-based embryo selection is more efficient than morphology-based selection in patients with advanced maternal age. Therefore, prohibition of the use of PGT-A had significant consequences on the efficiency and safety of IVF treatment in the country.

Expression of calcium pumps is differentially regulated by histone deacetylase inhibitors and estrogen receptor alpha in breast cancer cells.

BACKGROUND: Remodeling of Ca2+ signaling is an important step in cancer progression, and altered expression of members of the Ca2+ signaling toolkit including the plasma membrane Ca2+ ATPases (PMCA proteins encoded by ATP2B genes) is common in tumors. METHODS: In this study PMCAs were examined in breast cancer datasets and in a variety of breast cancer cell lines representing different subtypes. We investigated how estrogen receptor alpha (ER-α) and histone deacetylase (HDAC) inhibitors regulate the expression of these pumps. RESULTS: Three distinct datasets displayed significantly lower ATP2B4 mRNA expression in invasive breast cancer tissue samples compared to normal breast tissue, whereas the expression of ATP2B1 and ATP2B2 was not altered. Studying the protein expression profiles of Ca2+ pumps in a variety of breast cancer cell lines revealed low PMCA4b expression in the ER-α positive cells, and its marked upregulation upon HDAC inhibitor treatments. PMCA4b expression was also positively regulated by the ER-α pathway in MCF-7 cells that led to enhanced Ca2+ extrusion capacity in response to 17ß-estradiol (E2) treatment. E2-induced PMCA4b expression was further augmented by HDAC inhibitors. Surprisingly, E2 did not affect the expression of PMCA4b in other ER-α positive cells ZR-75-1, T-47D and BT-474. These findings were in good accordance with ChIP-seq data analysis that revealed an ER-α binding site in the ATP2B4 gene in MCF-7 cells but not in other ER-α positive tumor cells. In the triple negative cells PMCA4b expression was relatively high, and the effect of HDAC inhibitor treatment was less pronounced as compared to that of the ER-α positive cells. Although, the expression of PMCA4b was relatively high in the triple negative cells, a fraction of the protein was found in intracellular compartments that could interfere with the cellular function of the protein. CONCLUSIONS: Our results suggest that the expression of Ca2+ pumps is highly regulated in breast cancer cells in a subtype specific manner. Our results suggest that hormonal imbalances, epigenetic modifications and impaired protein trafficking could interfere with the expression and cellular function of PMCA4b in the course of breast cancer progression.

Histone Deacetylase Inhibitor Treatment Increases the Expression of the Plasma Membrane Ca2+ Pump PMCA4b and Inhibits the Migration of Melanoma Cells Independent of ERK.

Several new therapeutic options emerged recently to treat metastatic melanoma; however, the high frequency of intrinsic and acquired resistance among patients shows a need for new therapeutic options. Previously, we identified the plasma membrane Ca2+ ATPase 4b (PMCA4b) as a metastasis suppressor in BRAF-mutant melanomas and found that mutant BRAF inhibition increased the expression of the pump, which then inhibited the migratory and metastatic capability of the cells. Earlier it was also demonstrated that histone deacetylase inhibitors (HDACis) upregulated PMCA4b expression in gastric, colon, and breast cancer cells. In this study, we treated one BRAF wild-type and two BRAF-mutant melanoma cell lines with the HDACis, SAHA and valproic acid, either alone, or in combination with the BRAF inhibitor, vemurafenib. We found that HDACi treatment strongly increased the expression of PMCA4b in all cell lines irrespective of their BRAF mutational status, and this effect was independent of ERK activity. Furthermore, HDAC inhibition also enhanced the abundance of the housekeeping isoform PMCA1. Combination of HDACis with vemurafenib, however, did not have any additive effects on either PMCA isoform. We demonstrated that the HDACi-induced increase in PMCA abundance was coupled to an enhanced [Ca2+]i clearance rate and also strongly inhibited both the random and directional movements of A375 cells. The primary role of PMCA4b in these characteristic changes was demonstrated by treatment with the PMCA4-specific inhibitor, caloxin 1c2, which was able to restore the slower Ca2+ clearance rate and higher motility of the cells. While HDAC treatment inhibited cell motility, it decreased only modestly the ratio of proliferative cells and cell viability. Our results show that in melanoma cells the expression of both PMCA4b and PMCA1 is under epigenetic control and the elevation of PMCA4b expression either by HDACi treatment or by the decreased activation of the BRAF-MEK-ERK pathway can inhibit the migratory capacity of the highly motile A375 cells.

The plasma membrane Ca2+ pump PMCA4b inhibits the migratory and metastatic activity of BRAF mutant melanoma cells.

Oncogenic mutations of BRAF lead to constitutive ERK activity that supports melanoma cell growth and survival. While Ca2+ signaling is a well-known regulator of tumor progression, the crosstalk between Ca2+ signaling and the Ras-BRAF-MEK-ERK pathway is much less explored. Here we show that in BRAF mutant melanoma cells the abundance of the plasma membrane Ca2+ ATPase isoform 4b (PMCA4b, ATP2B4) is low at baseline but markedly elevated by treatment with the mutant BRAF specific inhibitor vemurafenib. In line with these findings gene expression microarray data also shows decreased PMCA4b expression in cutaneous melanoma when compared to benign nevi. The MEK inhibitor selumetinib-similarly to that of the BRAF-specific inhibitor-also increases PMCA4b levels in both BRAF and NRAS mutant melanoma cells suggesting that the MAPK pathway is involved in the regulation of PMCA4b expression. The increased abundance of PMCA4b in the plasma membrane enhances [Ca2+ ]i clearance from cells after Ca2+ entry. Moreover we show that both vemurafenib treatment and PMCA4b overexpression induce marked inhibition of migration of BRAF mutant melanoma cells. Importantly, reduced migration of PMCA4b expressing BRAF mutant cells is associated with a marked decrease in their metastatic potential in vivo. Taken together, our data reveal an important crosstalk between Ca2+ signaling and the MAPK pathway through the regulation of PMCA4b expression and suggest that PMCA4b is a previously unrecognized metastasis suppressor.

Multifaceted plasma membrane Ca(2+) pumps: From structure to intracellular Ca(2+) handling and cancer.

Plasma membrane Ca(2+) ATPases (PMCAs) are intimately involved in the control of intracellular Ca(2+) concentration. They reduce Ca(2+) in the cytosol not only by direct ejection, but also by controlling the formation of inositol-1,4,5-trisphosphate and decreasing Ca(2+) release from the endoplasmic reticulum Ca(2+) pool. In mammals four genes (PMCA1-4) are expressed, and alternative RNA splicing generates more than twenty variants. The variants differ in their regulatory characteristics. They localize into highly specialized membrane compartments and respond to the incoming Ca(2+) with distinct temporal resolution. The expression pattern of variants depends on cell type; a change in this pattern can result in perturbed Ca(2+) homeostasis and thus altered cell function. Indeed, PMCAs undergo remarkable changes in their expression pattern during tumorigenesis that might significantly contribute to the unbalanced Ca(2+) homeostasis of cancer cells. This article is part of a Special Issue entitled: Calcium and Cell Fate. Guest Editors: Jacques Haiech, Claus Heizmann, Joachim Krebs, Thierry Capiod and Olivier Mignen.

Plasma membrane Ca²âº-ATPases can shape the pattern of Ca²âº transients induced by store-operated Ca²âº entry.

Calcium (Ca(2+)) is a critical cofactor and signaling mediator in cells, and the concentration of cytosolic Ca(2+) is regulated by multiple proteins, including the plasma membrane Ca(2+)-ATPases (adenosine triphosphatases) (PMCAs), which use ATP to transport Ca(2+) out of cells. PMCA isoforms exhibit different kinetic and regulatory properties; thus, the presence and relative abundance of individual isoforms may help shape Ca(2+) transients and cellular responses. We studied the effects of three PMCA isoforms (PMCA4a, PMCA4b, and PMCA2b) on Ca(2+) transients elicited by conditions that trigger store-operated Ca(2+) entry (SOCE) and that blocked Ca(2+) uptake into the endoplasmic reticulum in HeLa cells, human embryonic kidney (HEK) 293 cells, or primary endothelial cell isolated from human umbilical cord veins (HUVECs). The slowly activating PMCA4b isoform produced long-lasting Ca(2+) oscillations in response to SOCE. The fast-activating isoforms PMCA2b and PMCA4a produced different effects. PMCA2b resulted in rapid and highly PMCA abundance-sensitive clearance of SOCE-mediated Ca(2+) transients, whereas PMCA4a reduced cytosolic Ca(2+), resulting in the establishment of a higher than baseline cytosolic Ca(2+) concentration. Mathematical modeling showed that slow activation was critical to the sustained oscillation induced by the "slow" PMCA4b pump. The modeling and experimental results indicated that the distinct properties of PMCA isoforms differentially regulate the pattern of SOCE-mediated Ca(2+) transients, which would thus affect the activation of downstream signaling pathways.

Histone deacetylase inhibitor- and PMA-induced upregulation of PMCA4b enhances Ca2+ clearance from MCF-7 breast cancer cells.

The expression of the plasma membrane Ca2+ ATPase (PMCA) isoforms is altered in several types of cancer cells suggesting that they are involved in cancer progression. In this study we induced differentiation of MCF-7 breast cancer cells by histone deacetylase inhibitors (HDACis) such as short chain fatty acids (SCFAs) or suberoylanilide hydroxamic acid (SAHA), and by phorbol 12-myristate 13-acetate (PMA) and found strong upregulation of PMCA4b protein expression in response to these treatments. Furthermore, combination of HDACis with PMA augmented cell differentiation and further enhanced PMCA4b expression both at mRNA and protein levels. Immunocytochemical analysis revealed that the upregulated protein was located mostly in the plasma membrane. To examine the functional consequences of elevated PMCA4b expression, the characteristics of intracellular Ca2+ signals were investigated before and after differentiation inducing treatments, and also in cells overexpressing PMCA4b. The increased PMCA4b expression - either by treatment or overexpression - led to enhanced Ca2+ clearance from the stimulated cells. We found pronounced PMCA4 protein expression in normal breast tissue samples highlighting the importance of this pump for the maintenance of mammary epithelial Ca2+ homeostasis. These results suggest that modulation of Ca2+ signaling by enhanced PMCA4b expression may contribute to normal development of breast epithelium and may be lost in cancer.

Apart from its known function, the plasma membrane Ca²âºATPase can regulate Ca²âº signaling by controlling phosphatidylinositol 4,5-bisphosphate levels.

Plasma membrane Ca(2+) ATPases (PMCAs, also known as ATP2B1-ATP2B4) are known targets of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2], but if and how they control the PtdIns(4,5)P2 pool has not been considered. We demonstrate here that PMCAs protect PtdIns(4,5)P2 in the plasma membrane from hydrolysis by phospholipase C (PLC). Comparison of active and inactive PMCAs indicates that the protection operates by two mechanisms; one requiring active PMCAs, the other not. It appears that the mechanism requiring activity is the removal of the Ca(2+) required for sustained PLC activity, whereas the mechanism not requiring activity is PtdIns(4,5)P2 binding. We show that in PMCA overexpressing cells, PtdIns(4,5)P2 binding can lead to less inositol 1,4,5-triphosphate (InsP3) and diminished Ca(2+) release from intracellular Ca(2+) pools. Inspection of a homology model of PMCA suggests that PMCAs have a conserved cluster of basic residues forming a 'blue collar' at the interface between the membrane core and the cytoplasmic domains. By molecular dynamics simulation, we found that the blue collar forms four binding pockets for the phosphorylated inositol head group of PtdIns(4,5)P2; these pockets bind PtdIns(4,5)P2 strongly and frequently. Our studies suggest that by having the ability to bind PtdIns(4,5)P2, PMCAs can control the accessibility of PtdIns(4,5)P2 for PLC and other PtdIns(4,5)P2-mediated processes.

A C-terminal di-leucine motif controls plasma membrane expression of PMCA4b.

Recent evidences show that the localization of different plasma membrane Ca(2+) ATPases (PMCAs) is regulated in various complex, cell type-specific ways. Here we show that in low-density epithelial and endothelial cells PMCA4b localized mostly in intracellular compartments and its plasma membrane localization was enhanced upon increasing density of cells. In good correlation with the enhanced plasma membrane localization a significantly more efficient Ca(2+) clearance was observed in confluent versus non-confluent HeLa cell cultures expressing mCherry-PMCA4b. We analyzed the subcellular localization and function of various C-terminally truncated PMCA4b variants and found that a truncated mutant PMCA4b-ct24 was mostly intracellular while another mutant, PMCA4b-ct48, localized more to the plasma membrane, indicating that a protein sequence corresponding to amino acid residues 1158-1181 contained a signal responsible for the intracellular retention of PMCA4b in non-confluent cultures. Alteration of three leucines to alanines at positions 1167-1169 resulted in enhanced cell surface expression and an appropriate Ca(2+) transport activity of both wild type and truncated pumps, suggesting that the di-leucine-like motif (1167)LLL was crucial in targeting PMCA4b. Furthermore, upon loss of cell-cell contact by extracellular Ca(2+) removal, the wild-type pump was translocated to the early endosomal compartment. Targeting PMCA4b to early endosomes was diminished by the L(1167-69)A mutation, and the mutant pump accumulated in long tubular cytosolic structures. In summary, we report a di-leucine-like internalization signal at the C-tail of PMCA4b and suggest an internalization-mediated loss of function of the pump upon low degree of cell-cell contact.

Gene expression divergence recapitulates the developmental hourglass model.

The observation that animal morphology tends to be conserved during the embryonic phylotypic period (a period of maximal similarity between the species within each animal phylum) led to the proposition that embryogenesis diverges more extensively early and late than in the middle, known as the hourglass model. This pattern of conservation is thought to reflect a major constraint on the evolution of animal body plans. Despite a wealth of morphological data confirming that there is often remarkable divergence in the early and late embryos of species from the same phylum, it is not yet known to what extent gene expression evolution, which has a central role in the elaboration of different animal forms, underpins the morphological hourglass pattern. Here we address this question using species-specific microarrays designed from six sequenced Drosophila species separated by up to 40 million years. We quantify divergence at different times during embryogenesis, and show that expression is maximally conserved during the arthropod phylotypic period. By fitting different evolutionary models to each gene, we show that at each time point more than 80% of genes fit best to models incorporating stabilizing selection, and that for genes whose evolutionarily optimal expression level is the same across all species, selective constraint is maximized during the phylotypic period. The genes that conform most to the hourglass pattern are involved in key developmental processes. These results indicate that natural selection acts to conserve patterns of gene expression during mid-embryogenesis, and provide a genome-wide insight into the molecular basis of the hourglass pattern of developmental evolution.

Cdc42 regulates myocardin-related transcription factor nuclear shuttling and alpha-smooth muscle actin promoter activity during renal tubular epithelial-mesenchymal transition.

BACKGROUND/AIMS: Epithelial-mesenchymal transition of tubular cells into alpha-smooth muscle actin (SMA)-expressing myofibroblasts is a central mechanism in tubulointerstitial fibrosis. Previously, a 'two-hit' model was proposed for epithelial-mesenchymal transition wherein an initial injury of the intercellular contacts and TGF-beta(1) are both required for SMA protein expression in LLC-PK1 cells. The Rho-Rho kinase-myosin light chain-myocardin-related transcription factor (MRTF)-serum response factor (SRF) pathway and Rac1, p21-activated kinase (PAK) and p38 were described as important regulators of MRTF localization and SMA expression. Cdc42 is another small G protein situated upstream of PAK and p38, and is activated upon cell contact disassembly. Here, we investigated its potential role in the regulation of MRTF nuclear shuttling and in the regulation of the SMA promoter. RESULTS: Transfection of a constitutive active (CA) Cdc42 construct alone induced the activation of the SMA promoter. The dominant negative (DN) Cdc42 construct prevented the activation of the promoter induced by cell contact disassembly, and reduced the combined effect of cell contact disruption and TGF-beta(1). SRF showed a marked nuclear accumulation in CA Cdc42-transfected cells. Cdc42 induced the nuclear translocation of MRTF, while DN Cdc42 inhibited its nuclear translocation induced by cell contact disassembly. Blocking PAK, MRTF and p38 by the corresponding DN constructs blunted the effects of CA Cdc42 on the SMA promoter. CONCLUSION: Cdc42 is involved in the regulation of SMA promoter activation through PAK, p38, MRTF and SRF. Cdc42 may be an important regulator of MRTF cellular localization.