Endothelial progenitor cells functionally express inward rectifier potassium channels

Jang, Seyong; Park, Jonghanne; Hur, Sung Won; Hong, Yong Tae; Hur, Jin; Chae, Jong Hee; Kim, Seung Ki; Kim, Jun; Kim, Hyo Soo; Kim, Sang Jeong

doi:10.1152/ajpcell.00002.2010

Cited by 19 publications

(16 citation statements)

References 52 publications

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“…2, E and F) Block by external Ba 2ϩ and Cs ϩ of native Kir currents in mouse MS cells. As described above, biophysical properties of native Kir currents in mouse MS cells were similar to those of the current cloned and native Kir currents, especially mediated by Kir2 subfamily members (Kir2.x) (7,14,19). Since it is well known that Kir2.x channels are inhibited by extracellular Ba 2ϩ in a manner that is dose-, voltage-, and time-dependent (Fig.…”

Section: Resultssupporting

confidence: 68%

Functional expression of a Kir2.1-like inwardly rectifying potassium channel in mouse mammary secretory cells

Kamikawa

Ishikawa

2014

American Journal of Physiology-Cell Physiology

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K(+) channels in mammary secretory (MS) cells are believed to play a role in transcellular electrolyte transport and thus determining ionic composition of the aqueous phase of milk. However, direct evidence for specific K(+) channel activity in native MS cells is lacking at the single-cell level. Here, we show for the first time that an inwardly rectifying K(+) (Kir) channel is functionally expressed in fully differentiated MS cells that were freshly isolated from the mammary gland of lactating mice. Using the standard whole cell patch-clamp technique, we found that mouse MS cells consistently displayed a K(+) current, whose electrophysiological properties are similar to those previously reported for Kir2.x channels, particularly Kir2.1: 1) current-voltage relationship with strong inward rectification, 2) slope conductance approximately proportional to the square root of external K(+) concentration, 3) voltage- and time-dependent and high-affinity block by external Ba(2+), and 4) voltage-dependent inhibition by external Cs(+). Accordingly, RT-PCR analysis revealed the gene expression of Kir2.1, but not Kir2.2, Kir2.3, and Kir2.4, in lactating mouse mammary gland, and immunohistochemical staining showed Kir2.1 protein expression in the secretory cells. Cell-attached patch recordings from MS cells revealed that a 31-pS K(+) channel with strong inward rectification was likely active at the resting membrane potential. Collectively, the present work demonstrates that a functional Kir2.1-like channel is expressed in lactating mouse MS cells. We propose that the channel might be involved, at least in part, in secretion and/or preservation of ionic components of milk stored into the lumen of these cells.

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Section: Resultssupporting

confidence: 68%

Functional expression of a Kir2.1-like inwardly rectifying potassium channel in mouse mammary secretory cells

Kamikawa

Ishikawa

2014

American Journal of Physiology-Cell Physiology

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“…A more hyperpolarized V M would enhance the electrochemical gradient driving Ca 2+ entry into the cytosol, thereby resulting in a larger increase in [Ca 2+ ] i [17]. The V M in ECFCs is mainly set by K + conductance [32]. PMF-EPCs were, therefore, exposed to a solution containing 100 mM KCl (high-K + ) to clamp both types of cells at the same V M of about 0 mV, as indicated by the Nernst equation for K + , E K = (−RT/F)*ln([K + ] o /[K + ] i ).…”

Section: Resultsmentioning

confidence: 99%

Enhanced Expression of Stim, Orai, and TRPC Transcripts and Proteins in Endothelial Progenitor Cells Isolated from Patients with Primary Myelofibrosis

et al. 2014

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BackgroundAn increase in the frequency of circulating endothelial colony forming cells (ECFCs), the only subset of endothelial progenitor cells (EPCs) truly belonging to the endothelial phenotype, occurs in patients affected by primary myelofibrosis (PMF). Herein, they might contribute to the enhanced neovascularisation of fibrotic bone marrow and spleen. Store-operated Ca2+ entry (SOCE) activated by the depletion of the inositol-1,4,5-trisphosphate (InsP3)-sensitive Ca2+ store drives proliferation in ECFCs isolated from both healthy donors (N-ECFCs) and subjects suffering from renal cellular carcinoma (RCC-ECFCs). SOCE is up-regulated in RCC-ECFCs due to the over-expression of its underlying molecular components, namely Stim1, Orai1, and TRPC1.Methodology/Principal FindingsWe utilized Ca2+ imaging, real-time polymerase chain reaction, western blot analysis and functional assays to evaluate molecular structure and the functional role of SOCE in ECFCs derived from PMF patients (PMF-ECFCs). SOCE, induced by either pharmacological (i.e. cyclopiazonic acid or CPA) or physiological (i.e. ATP) stimulation, was significantly higher in PMF-ECFCs. ATP-induced SOCE was inhibited upon blockade of the phospholipase C/InsP3 signalling pathway with U73111 and 2-APB. The higher amplitude of SOCE was associated to the over-expression of the transcripts encoding for Stim2, Orai2–3, and TRPC1. Conversely, immunoblotting revealed that Stim2 levels remained constant as compared to N-ECFCs, while Stim1, Orai1, Orai3, TRPC1 and TRPC4 proteins were over-expressed in PMF-ECFCs. ATP-induced SOCE was inhibited by BTP-2 and low micromolar La3+ and Gd3+, while CPA-elicited SOCE was insensitive to Gd3+. Finally, BTP-2 and La3+ weakly blocked PMF-ECFC proliferation, while Gd3+ was ineffective.ConclusionsTwo distinct signalling pathways mediate SOCE in PMF-ECFCs; one is activated by passive store depletion and is Gd3+-resistant, while the other one is regulated by the InsP3-sensitive Ca2+ pool and is inhibited by Gd3+. Unlike N- and RCC-ECFCs, the InsP3-dependent SOCE does not drive PMF-ECFC proliferation.

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“…The opening of potassium channels in the cell membrane produces a hyperpolarization of membrane potential which is required for the progression through the cell cycle. As a consequence in the presence of potassium channel blockers cell proliferation is inhibited [34,35]. Woodfort et al early determined that different potassium channel antagonists, as Gli, produce a concentration-dependent growth inhibition on MCF-7 cells with a significant arrest of cells in G0/G1 phase [36].…”

Section: Discussionmentioning

confidence: 99%

Glibenclamide inhibits cell growth by inducing G0/G1 arrest in the human breast cancer cell line MDA-MB-231

Núñez

Medina

Cricco

et al. 2013

BMC Pharmacol Toxicol

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BackgroundGlibenclamide (Gli) binds to the sulphonylurea receptor (SUR) that is a regulatory subunit of ATP-sensitive potassium channels (KATP channels). Binding of Gli to SUR produces the closure of KATP channels and the inhibition of their activity. This drug is widely used for treatment of type 2-diabetes and it has been signaled as antiproliferative in several tumor cell lines. In previous experiments we demonstrated the antitumoral effect of Gli in mammary tumors induced in rats. The aim of the present work was to investigate the effect of Gli on MDA-MB-231 breast cancer cell proliferation and to examine the possible pathways involved in this action.ResultsThe mRNA expression of the different subunits that compose the KATP channels was evaluated in MDA-MB-231 cells by reverse transcriptase-polymerase chain reaction. Results showed the expression of mRNA for both pore-forming isoforms Kir6.1 and Kir6.2 and for the regulatory isoform SUR2B in this cell line. Gli inhibited cell proliferation assessed by a clonogenic method in a dose dependent manner, with an increment in the population doubling time. The KATP channel opener minoxidil increased clonogenic proliferation, effect that was counteracted by Gli. When cell cycle analysis was performed by flow cytometry, Gli induced a significant cell-cycle arrest in G0/G1 phase, together with an up-regulation of p27 levels and a diminution in cyclin E expression, both evaluated by immunoblot. However, neither differentiation evaluated by neutral lipid accumulation nor apoptosis assessed by different methodologies were detected. The cytostatic, non toxic effect on cell proliferation was confirmed by removal of the drug.Combination treatment of Gli with tamoxifen or doxorubicin showed an increment in the antiproliferative effect only for doxorubicin.ConclusionsOur data clearly demonstrated a cytostatic effect of Gli in MDA-MB-231 cells that may be mediated through KATP channels, associated to the inhibition of the G1-S phase progression. In addition, an interesting observation about the effect of the combination of Gli with doxorubicin leads to future research for a potential novel role for Gli as an adjuvant in breast cancer treatment

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Endothelial progenitor cells functionally express inward rectifier potassium channels

Cited by 19 publications

References 52 publications

Functional expression of a Kir2.1-like inwardly rectifying potassium channel in mouse mammary secretory cells

Functional expression of a Kir2.1-like inwardly rectifying potassium channel in mouse mammary secretory cells

Enhanced Expression of Stim, Orai, and TRPC Transcripts and Proteins in Endothelial Progenitor Cells Isolated from Patients with Primary Myelofibrosis

Glibenclamide inhibits cell growth by inducing G0/G1 arrest in the human breast cancer cell line MDA-MB-231

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