A novel function of phosphate-mediated intracellular signal transduction pathways.
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Animals↗
Biomedical subjects
Masashi Isshiki
Publications and source records attributed to Masashi Isshiki.
[Hypertension and intracellular Ca2+ signalling].
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Animals↗
Impaired flow-dependent control of vascular tone and remodeling in P2X4-deficient mice.
The structure and function of blood vessels adapt to environmental changes such as physical development and exercise. This phenomenon is based on the ability of the endothelial cells to sense and respond to blood flow; however, the underlying mechanisms remain unclear. Here we show that the ATP-gated P2X4 ion channel, expressed on endothelial cells and encoded by P2rx4 in mice, has a key role in the response of endothelial cells to changes in blood flow. P2rx4(-/-) mice do not have normal endothelial cell responses to flow, such as influx of Ca(2+) and subsequent production of the potent vasodilator nitric oxide (NO). Additionally, vessel dilation induced by acute increases in blood flow is markedly suppressed in P2rx4(-/-) mice. Furthermore, P2rx4(-/-) mice have higher blood pressure and excrete smaller amounts of NO products in their urine than do wild-type mice. Moreover, no adaptive vascular remodeling, that is, a decrease in vessel size in response to a chronic decrease in blood flow, was observed in P2rx4(-/-) mice. Thus, endothelial P2X4 channels are crucial to flow-sensitive mechanisms that regulate blood pressure and vascular remodeling.
Acetylcholine↗
Subcortical Ca2+ waves sneaking under the plasma membrane in endothelial cells.
Subplasmalemmal Ca2+, dynamically equilibrated with extracellular Ca2+, affects numerous signaling molecules, effectors, and events within this restricted space. We demonstrated the presence of a novel Ca2+ wave propagating beneath the plasma membrane in response to acute elevation of extracellular [Ca2+], by targeting a Ca2+ sensor, cameleon, to the endothelial plasmalemma. These subcortical waves, spatially distinct from classical cytosolic Ca2+ waves, originated in localized regions and propagated throughout the subplasmalemma. Translocation of an expressed GFP fused with a PH domain of PLC from the plasma membrane to the cytosol accompanied these subcortical waves, and U73122 attenuated not only the GFP-PH translocation, but also the peak amplitude of the subcortical Ca2+ waves; this finding suggests the involvement of local IP3 production through PLC-mediated PIP2 hydrolysis in the initiation of these waves. Changes in NO production as well as PKCbeta-GFP translocation from the cytosol to the plasma membrane, but not of GFP-PLA2 to perinuclear endomembranes, were associated with the subplasmalemmal Ca2+ changes. Thus, extracellular Ca2+ maintains the basal PLC activity of the plasma membrane, is involved in the initiation of compartmentalized subcortical Ca2+ waves, and regulates Ca2+-dependent signaling molecules residing in or translocated to the plasma membrane. The full text of this article is available online at http://circres.ahajournals.org.
Amino Acid Motifs↗
Two cases of renovascular hypertension and ischemic renal dysfunction: reliable choice of examinations and treatments.
We experienced two aged patients with atherosclerotic renovascular stenosis associated with hypertension and ischemic nephropathy. Both patients exhibited sudden rise in blood pressure (BP) and progressive aggravation of renal dysfunction. In these patients, the use of contrast medium to screen for renal artery stenosis (RAS) ran the risk of further deterioration of renal function. We therefore used magnetic resonance angiography (MRA), which is less conducive to renal damage, to screen for RAS. One-sided RAS was treated by percutaneous transluminal angioplasty of the renal artery (PTRA) and stenting. As a result, BP decreased in both patients. Serum creatinine (Cr) decreased slightly in one patient, whereas, in the other, serum Cr increased transiently and then decreased and stabilized to pre-treatment levels. Thus, although it is unclear whether the combination of PTRA and stenting is among the best treatments for patients with RAS and moderate-to-severe renal dysfunction, PTRA and stenting are clearly of benefit in selected patients. In addition, recent progress in characterizing the pathophysiology of ischemic nephropathy associated with renovascular hypertension has created interest in the therapeutic potential of angiotensin II receptor antagonists, sympatholytic agents, and antioxidants. Therefore, we discuss the therapeutic utility of PTRA and stenting and the above-mentioned medications in patients with RAS and renal dysfunction.
Angioplasty, Balloon↗
Increase in IP3 and intracellular Ca2+ induced by phosphate depletion in LLC-PK 1 cells.
The mechanisms by which Pi depletion rapidly regulates gene expression and cellular function have not been clarified. Here, we found a rapid increase in intracellular ionized calcium [Ca(2+)](i) by phosphate depletion in LLC-PK(1) cells using confocal microscopy with the green-fluorescence protein based calcium indicator "yellow cameleon 2.1." The increase of [Ca(2+)](i) was observed in the presence or absence of extracellular Ca(2+). At the same time, an approximately twofold increase in intracellular inositol 1,4,5-triphosphate (IP(3)) occurred in response to the acute Pi depletion in the medium. Furthermore, 2-aminoethoxydiphenyl borate completely blocked the [Ca(2+)](i) increase induced by Pi depletion. These results suggest that Pi depletion causes IP(3)-mediated release of Ca(2+) from intracellular Ca(2+) pools and rapidly increases [Ca(2+)](i) in LLC-PK(1) cells.
Animals↗
Function of caveolae in Ca2+ entry and Ca2+-dependent signal transduction.
The correct spatial and temporal control of Ca2+ signaling is essential for such cellular activities as fertilization, secretion, motility, and cell division. There has been a long-standing interest in the role of caveolae in regulating intracellular Ca2+ concentration. In this review we provide an updated view of how caveolae may regulate both Ca2+ entry into cells and Ca2+-dependent signal transduction
Animals↗
A molecular sensor detects signal transduction from caveolae in living cells.
Biochemical and cell fractionation studies suggest caveolae contain functionally organized sets of signaling molecules that are capable of transmitting specific signals to the cell. It is not known, however, whether any signals actually originate from caveolae in living cells. To address this question, we have engineered the calcium sensor yellow cameleon so that it is targeted either to the plasma membrane, caveolae, or the cytoplasm of endothelial cells. Quantitative measurements of the three Ca2+ pools detected by these probes indicate that caveolae are preferred sites of Ca2+ entry when Ca2+ stores in the endoplasmic reticulum are depleted. These results suggest that the signaling machinery in control of Ca2+ entry is functionally organized in the caveolae of living cells.
Animals↗
Sites of Ca(2+) wave initiation move with caveolae to the trailing edge of migrating cells.
The caveola is a membrane domain that compartmentalizes signal transduction at the cell surface. Normally in endothelial cells, groups of caveolae are found clustered along stress fibers or at the lateral margins in all regions of the cell. Subsets of these clusters appear to contain the signaling machinery for initiating Ca(2+) wave formation. Here we report that induction of cell migration, either by wounding a cell monolayer or by exposing cells to laminar shear stress, causes caveolae to move to the trailing edge of the cell. Concomitant with the relocation of the caveolae, sites of Ca(2+) wave initiation move to the same location. In as much as the relocated caveolae contain elements of the signaling machinery required for ATP-stimulated release of Ca(2+) from the ER, these results suggest that caveolae function as containers that carry this machinery to different cellular locations.
Actins↗
Induction and activation of the transcription factor NFATc1 (NFAT2) integrate RANKL signaling in terminal differentiation of osteoclasts.
Signaling by RANKL is essential for terminal differentiation of monocytes/macrophages into osteoclasts. The TRAF6 and c-Fos signaling pathways both play important roles downstream of RANKL. We show here that RANKL selectively induces NFATc1 expression via these two pathways. RANKL also evokes Ca(2+) oscillations that lead to calcineurin-mediated activation of NFATc1, and therefore triggers a sustained NFATc1-dependent transcriptional program during osteoclast differentiation. We also show that NFATc1-deficient embryonic stem cells fail to differentiate into osteoclasts in response to RANKL stimulation, and that ectopic expression of NFATc1 causes precursor cells to undergo efficient differentiation without RANKL signaling. Thus, NFATc1 may represent a master switch for regulating terminal differentiation of osteoclasts, functioning downstream of RANKL.
Active Transport, Cell Nucleus↗