{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,14]],"date-time":"2026-03-14T03:19:18Z","timestamp":1773458358372,"version":"3.50.1"},"reference-count":63,"publisher":"Rockefeller University Press","issue":"1","content-domain":{"domain":["rupress.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2008,7,1]]},"abstract":"<jats:p>Ca2+ sparks are highly localized, transient releases of Ca2+ from sarcoplasmic reticulum through ryanodine receptors (RyRs). In smooth muscle, Ca2+ sparks trigger spontaneous transient outward currents (STOCs) by opening nearby clusters of large-conductance Ca2+-activated K+ channels, and also gate Ca2+-activated Cl\u2212 (Cl(Ca)) channels to induce spontaneous transient inward currents (STICs). While the molecular mechanisms underlying the activation of STOCs by Ca2+ sparks is well understood, little information is available on how Ca2+ sparks activate STICs. In the present study, we investigated the spatial organization of RyRs and Cl(Ca) channels in spark sites in airway myocytes from mouse. Ca2+ sparks and STICs were simultaneously recorded, respectively, with high-speed, widefield digital microscopy and whole-cell patch-clamp. An image-based approach was applied to measure the Ca2+ current underlying a Ca2+ spark (ICa(spark)), with an appropriate correction for endogenous fixed Ca2+ buffer, which was characterized by flash photolysis of NPEGTA. We found that ICa(spark) rises to a peak in 9 ms and decays with a single exponential with a time constant of 12 ms, suggesting that Ca2+ sparks result from the nonsimultaneous opening and closure of multiple RyRs. The onset of the STIC lags the onset of the ICa(spark) by less than 3 ms, and its rising phase matches the duration of the ICa(spark). We further determined that Cl(Ca) channels on average are exposed to a [Ca2+] of 2.4 \u03bcM or greater during Ca2+ sparks. The area of the plasma membrane reaching this level is &amp;lt;600 nm in radius, as revealed by the spatiotemporal profile of [Ca2+] produced by a reaction-diffusion simulation with measured ICa(spark). Finally we estimated that the number of Cl(Ca) channels localized in Ca2+ spark sites could account for all the Cl(Ca) channels in the entire cell. Taken together these results lead us to propose a model in which RyRs and Cl(Ca) channels in Ca2+ spark sites localize near to each other, and, moreover, Cl(Ca) channels concentrate in an area with a radius of \u223c600 nm, where their density reaches as high as 300 channels\/\u03bcm2. This model reveals that Cl(Ca) channels are tightly controlled by Ca2+ sparks via local Ca2+ signaling.<\/jats:p>","DOI":"10.1085\/jgp.200709933","type":"journal-article","created":{"date-parts":[[2008,6,30]],"date-time":"2008-06-30T19:48:39Z","timestamp":1214855319000},"page":"145-160","update-policy":"https:\/\/doi.org\/10.1085\/jgp.crossmarkpolicy","source":"Crossref","is-referenced-by-count":51,"title":["A Close Association of RyRs with Highly Dense Clusters of Ca2+-activated Cl\u2212 Channels Underlies the Activation of STICs by Ca2+ Sparks in Mouse Airway Smooth Muscle"],"prefix":"10.1085","volume":"132","author":[{"given":"Rongfeng","family":"Bao","sequence":"first","affiliation":[{"name":"Biomedical Imaging Group and Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01655"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lawrence M.","family":"Lifshitz","sequence":"additional","affiliation":[{"name":"Biomedical Imaging Group and Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01655"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Richard A.","family":"Tuft","sequence":"additional","affiliation":[{"name":"Biomedical Imaging Group and Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01655"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Karl","family":"Bellve\u0301","sequence":"additional","affiliation":[{"name":"Biomedical Imaging Group and Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01655"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kevin E.","family":"Fogarty","sequence":"additional","affiliation":[{"name":"Biomedical Imaging Group and Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01655"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ronghua","family":"ZhuGe","sequence":"additional","affiliation":[{"name":"Biomedical Imaging Group and Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01655"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"291","published-online":{"date-parts":[[2008,6,30]]},"reference":[{"key":"2023072920542321100_BIB1","doi-asserted-by":"crossref","first-page":"965","DOI":"10.1161\/01.RES.0000100068.43006.36","volume":"93","year":"2003","journal-title":"Circ. 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