Inhibition of SERCA pumps induces desynchronized RyR activation in overloaded internal Ca2+ stores in smooth muscle cells

2010 ◽  
Vol 298 (5) ◽  
pp. C1038-C1046 ◽  
Author(s):  
Norma Leticia Gómez-Viquez ◽  
Guadalupe Guerrero-Serna ◽  
Fernando Arvizu ◽  
Ubaldo García ◽  
Agustín Guerrero-Hernández
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Smooth Muscle Cells ◽  
Ryanodine Receptors ◽  
Muscle Cells ◽  
Local Communication ◽  
Outward Currents ◽  
Serca Pump

We have previously shown that rapid inhibition of sarcoplasmic reticulum (SR) ATPase (SERCA pumps) decreases the amplitude and rate of rise (synchronization) of caffeine induced-Ca2+ release without producing a reduction of free luminal SR Ca2+ level in smooth muscle cells (Gómez-Viquez L, Guerrero-Serna G, García U, Guerrero-Hernández A. Biophys J 85: 370–380, 2003). Our aim was to investigate the role of luminal SR Ca2+ content in the communication between ryanodine receptors (RyRs) and SERCA pumps. To this end, we studied the effect of SERCA pump inhibition on RyR-mediated Ca2+ release in smooth muscle cells with overloaded SR Ca2+ stores. Under this condition, the amplitude of RyR-mediated Ca2+ release was not affected but the rate of rise was still decreased. In addition, the caffeine-induced Ca2+-dependent K+ outward currents revealed individual events, suggesting that SERCA pump inhibition reduces the coordinated activation of RyRs. Collectively, our results indicate that SERCA pumps facilitate the activation of RyRs by a mechanism that does not involve the regulation of SR Ca2+ content. Importantly, SERCA pumps and RyRs colocalize in smooth muscle cells, suggesting a possible local communication between these two proteins.

scholarly journals The Influence of Sarcoplasmic Reticulum Ca2+ Concentration on Ca2+ Sparks and Spontaneous Transient Outward Currents in Single Smooth Muscle Cells

1999 ◽  
Vol 113 (2) ◽  
pp. 215-228 ◽  
Author(s):  
Ronghua ZhuGe ◽  
Richard A. Tuft ◽  
Kevin E. Fogarty ◽  
Karl Bellve ◽  
Fredric S. Fay ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Potassium Channels ◽  
Smooth Muscle Cells ◽  
High Speed ◽  
Muscle Cells ◽  
Wide Field ◽  
Outward Currents ◽  
The Relationship ◽  
Spontaneous Transient Outward Currents

Localized, transient elevations in cytosolic Ca2+, known as Ca2+ sparks, caused by Ca2+ release from sarcoplasmic reticulum, are thought to trigger the opening of large conductance Ca2+-activated potassium channels in the plasma membrane resulting in spontaneous transient outward currents (STOCs) in smooth muscle cells. But the precise relationships between Ca2+ concentration within the sarcoplasmic reticulum and a Ca2+ spark and that between a Ca2+ spark and a STOC are not well defined or fully understood. To address these problems, we have employed two approaches using single patch-clamped smooth muscle cells freshly dissociated from toad stomach: a high speed, wide-field imaging system to simultaneously record Ca2+ sparks and STOCs, and a method to simultaneously measure free global Ca2+ concentration in the sarcoplasmic reticulum ([Ca2+]SR) and in the cytosol ([Ca2+]CYTO) along with STOCs. At a holding potential of 0 mV, cells displayed Ca2+ sparks and STOCs. Ca2+ sparks were associated with STOCs; the onset of the sparks coincided with the upstroke of STOCs, and both had approximately the same decay time. The mean increase in [Ca2+]CYTO at the time and location of the spark peak was ∼100 nM above a resting concentration of ∼100 nM. The frequency and amplitude of spontaneous Ca2+ sparks recorded at −80 mV were unchanged for a period of 10 min after removal of extracellular Ca2+ (nominally Ca2+-free solution with 50 μM EGTA), indicating that Ca2+ influx is not necessary for Ca2+sparks. A brief pulse of caffeine (20 mM) elicited a rapid decrease in [Ca2+]SR in association with a surge in [Ca2+]CYTO and a fusion of STOCs, followed by a fast restoration of [Ca2+]CYTO and a gradual recovery of [Ca2+]SR and STOCs. The return of global [Ca2+]CYTO to rest was an order of magnitude faster than the refilling of the sarcoplasmic reticulum with Ca2+. After the global [Ca2+]CYTO was fully restored, recovery of STOC frequency and amplitude were correlated with the level of [Ca2+]SR, even though the time for refilling varied greatly. STOC frequency did not recover substantially until the [Ca2+]SR was restored to 60% or more of resting levels. At [Ca2+]SR levels above 80% of rest, there was a steep relationship between [Ca2+]SR and STOC frequency. In contrast, the relationship between [Ca2+]SR and STOC amplitude was linear. The relationship between [Ca2+]SR and the frequency and amplitude was the same for Ca2+ sparks as it was for STOCs. The results of this study suggest that the regulation of [Ca2+]SR might provide one mechanism whereby agents could govern Ca2+ sparks and STOCs. The relationship between Ca2+ sparks and STOCs also implies a close association between a sarcoplasmic reticulum Ca2+ release site and the Ca2+-activated potassium channels responsible for a STOC.

Role of sarcoplasmic reticulum Ca 2+ content in Ca 2+ entry of bovine airway smooth muscle cells

2003 ◽  
Vol 368 (4) ◽  
pp. 277-283 ◽  
Author(s):  
Blanca Baz�n-Perkins ◽  
Edgar Flores-Soto ◽  
Carlos Barajas-L�pez ◽  
Luis M. Monta�o
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Smooth Muscle Cells ◽  
Airway Smooth Muscle ◽  
Muscle Cells ◽  
Airway Smooth Muscle Cells

Ca2+Release through Ryanodine Receptors in the Sarcoplasmic Reticulum and Ca2+Sequestration by the Mitochondria in Smooth Muscle Cells

2003 ◽  
Vol 35 (3/4) ◽  
pp. 169-174
Author(s):  
Yuji Imaizumi ◽  
Yoshiaki Ohi ◽  
Hisao Yamamura ◽  
Kozo Morimura ◽  
Katsuhiko Muraki
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Smooth Muscle Cells ◽  
Ryanodine Receptors ◽  
Muscle Cells

scholarly journals Simultaneous measurement of Ca2+ release and influx into smooth muscle cells in response to caffeine. A novel approach for calculating the fraction of current carried by calcium.

1994 ◽  
Vol 104 (2) ◽  
pp. 395-422 ◽  
Author(s):  
A Guerrero ◽  
J J Singer ◽  
F S Fay
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Sarcoplasmic Reticulum ◽  
Smooth Muscle Cells ◽  
Surface Membrane ◽  
Ryanodine Receptors ◽  
Preceding Paper ◽  
Muscle Cells ◽  
Ionic Currents ◽  
Membrane Channels

Activation of ryanodine receptors on the sarcoplasmic reticulum of single smooth muscle cells from the stomach muscularis of Bufo marinus by caffeine is accompanied by a rise in cytoplasmic [Ca2+] ([Ca2+]i), and the opening of nonselective cationic plasma membrane channels. To understand how each of these pathways contributes to the rise in [Ca2+]i, one needs to separately monitor Ca2+ entry through them. Such information was obtained from simultaneous measurements of ionic currents and [Ca2+]i by the development of a novel and general method to assess the fraction of current induced by an agonist that is carried by Ca2+. Application of this method to the currents induced in these smooth muscle cells by caffeine revealed that approximately 20% of the current passing through the membrane channels activated following caffeine application is carried by Ca2+. Based on this information we found that while Ca2+ entry through these channels rises slowly, release of Ca2+ from stores, while starting at the same time, is much faster and briefer. Detailed quantitative analysis of the Ca2+ release from stores suggests that it most likely decays due to depletion of Ca2+ in those stores. When caffeine was applied twice to a cell with only a brief (30 s) interval in between, the amount of Ca2+ released from stores was markedly diminished following the second caffeine application whereas the current carried in part by Ca2+ entry across the plasma membrane was not significantly affected. These and other studies described in the preceding paper indicate that activation of the nonselective cation plasma membrane channels in response to caffeine was not caused as a consequence of emptying of internal Ca2+ stores. Rather, it is proposed that caffeine activates these membrane channels either by direct interaction or alternatively by a linkage between ryanodine receptors on the sarcoplasmic reticulum and the nonselective cation channels on the surface membrane.

scholarly journals Local Ca2+ coupling between mitochondria and sarcoplasmic reticulum following depolarization in guinea pig urinary bladder smooth muscle cells

2018 ◽  
Vol 314 (1) ◽  
pp. C88-C98 ◽  
Author(s):  
Hisao Yamamura ◽  
Keisuke Kawasaki ◽  
Sou Inagaki ◽  
Yoshiaki Suzuki ◽  
Yuji Imaizumi
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Urinary Bladder ◽  
Guinea Pig ◽  
Smooth Muscle Cells ◽  
Ryanodine Receptors ◽  
Muscle Cells ◽  
Bladder Smooth Muscle ◽  
Voltage Dependent ◽  
Urinary Bladder Smooth Muscle

Spatiotemporal changes in cytosolic Ca2+ concentration ([Ca2+]c) trigger a number of physiological functions in smooth muscle cells (SMCs). We previously imaged Ca2+-induced Ca2+ release following membrane depolarization as local Ca2+ transients, Ca2+ hotspots, in subplasmalemmal regions. In this study, the physiological significance of mitochondria on local Ca2+ signaling was examined. Cytosolic and mitochondrial Ca2+ images following depolarization or action potentials were recorded in single SMCs from the guinea pig urinary bladder using a fast-scanning confocal fluorescent microscope. Depolarization- and action potential-induced [Ca2+]c transients occurred at several discrete sites in subplasmalemmal regions, peaked within 30 ms, and then spread throughout the whole-cell. In contrast, Ca2+ concentration in the mitochondria matrix ([Ca2+]m) increased after a delay of ~50 ms from the start of depolarization, and then peaked within 500 ms. Following repolarization, [Ca2+]c returned to the resting level with a half-decay time of ~500 ms, while [Ca2+]m recovered more slowly (∼1.5 s). Carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone, a mitochondrial uncoupler, abolished depolarization-induced [Ca2+]m elevations and slowed [Ca2+]c changes. Importantly, short depolarization-induced changes in [Ca2+]m and transmembrane potential in mitochondria coupled to Ca2+ hotspots were significantly larger than those in other mitochondria. Total internal reflection fluorescence imaging revealed that a subset of mitochondria closely localized with ryanodine receptors and voltage-dependent Ca2+ channels. These results indicate that particular mitochondria are functionally coupled to ion channels and sarcoplasmic reticulum fragments within the local Ca2+ microdomain, and thus, strongly contribute to [Ca2+]c regulation in SMCs.

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