Clearance of store-released Ca2+ by the Na+-Ca 2+ exchanger is diminished in aortic smooth muscle from Na +-K+-ATPase α2-isoform gene-ablated mice

Ron Lynch, Craig S. Weber, Kevin D. Nullmeyer, Edwin D W Moore, Richard J. Paul

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Two α-isoforms of the Na+-K+-ATPase are expressed in vascular smooth muscle cells (VSMCs). The α1- isoform is proposed to serve a cytosolic housekeeping role, whereas the α2-isoform modulates Ca2+ storage via coupling to the Na+-Ca2+ exchanger (NCX) in a subsarcolemmal compartment. To evaluate the ramifications of this proposed interaction, Ca 2+-store load and the contributions of the primary Ca2+ transporters to Ca2+ clearance were studied in aortic VSMCs from embryonic wild-type (WT) and Na+-K+-ATPase α2-isoform gene-ablated, homozygous null knockout (α2-KO) mice. Ca2+ stores were unloaded by inhibiting the sarco(endo)plasmic reticulum Ca2+-ATPase with cyclopiazonic acid (CPA) in Ca2+-free media to limit Ca2+ influx. Ca2+ clearance by the plasma membrane Ca2+-ATPase (PMCA), NCX, or mitochondria was selectively inhibited. In WT VSMCs, NCX accounted for 90% of the Ca2+ efflux. In α2-KO VSMCs, preferential clearance of store-released Ca2+ by NCX was lost, whereas PMCA activity was increased. Selective inhibition of the α2-isoform (0.5 μM ouabain for 20 min), before treatment with CPA enhanced the store load in VSMCs from WT, but not α2- KO mice. A subsequent analysis of capacitative Ca2+ entry (CCE) indicated that the magnitude of Ca2+ influx was significantly greater in α2-KO cells. Our findings support the concept of a subsarcolemmal space where the α2-isoform coupled with NCX modulates Ca2+-store function and, thereby, CCE.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume294
Issue number3
DOIs
StatePublished - Mar 2008

Fingerprint

Sodium-Calcium Exchanger
Smooth Muscle
Vascular Smooth Muscle
Protein Isoforms
Smooth Muscle Myocytes
Calcium-Transporting ATPases
Genes
Cell Membrane
Housekeeping
Reticulum
Ouabain
sodium-translocating ATPase
Mitochondria

Keywords

  • Calcium homeostasis
  • Calcium stores
  • Capacitative calcium influx
  • Plasma membrane calcium ATPase
  • Sarco(endo)plasmic reticulum calcium ATPase

ASJC Scopus subject areas

  • Physiology

Cite this

Clearance of store-released Ca2+ by the Na+-Ca 2+ exchanger is diminished in aortic smooth muscle from Na +-K+-ATPase α2-isoform gene-ablated mice. / Lynch, Ron; Weber, Craig S.; Nullmeyer, Kevin D.; Moore, Edwin D W; Paul, Richard J.

In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 294, No. 3, 03.2008.

Research output: Contribution to journalArticle

@article{c6e709ff8f96448da7ee5d0b9c9fa8d7,
title = "Clearance of store-released Ca2+ by the Na+-Ca 2+ exchanger is diminished in aortic smooth muscle from Na +-K+-ATPase α2-isoform gene-ablated mice",
abstract = "Two α-isoforms of the Na+-K+-ATPase are expressed in vascular smooth muscle cells (VSMCs). The α1- isoform is proposed to serve a cytosolic housekeeping role, whereas the α2-isoform modulates Ca2+ storage via coupling to the Na+-Ca2+ exchanger (NCX) in a subsarcolemmal compartment. To evaluate the ramifications of this proposed interaction, Ca 2+-store load and the contributions of the primary Ca2+ transporters to Ca2+ clearance were studied in aortic VSMCs from embryonic wild-type (WT) and Na+-K+-ATPase α2-isoform gene-ablated, homozygous null knockout (α2-KO) mice. Ca2+ stores were unloaded by inhibiting the sarco(endo)plasmic reticulum Ca2+-ATPase with cyclopiazonic acid (CPA) in Ca2+-free media to limit Ca2+ influx. Ca2+ clearance by the plasma membrane Ca2+-ATPase (PMCA), NCX, or mitochondria was selectively inhibited. In WT VSMCs, NCX accounted for 90{\%} of the Ca2+ efflux. In α2-KO VSMCs, preferential clearance of store-released Ca2+ by NCX was lost, whereas PMCA activity was increased. Selective inhibition of the α2-isoform (0.5 μM ouabain for 20 min), before treatment with CPA enhanced the store load in VSMCs from WT, but not α2- KO mice. A subsequent analysis of capacitative Ca2+ entry (CCE) indicated that the magnitude of Ca2+ influx was significantly greater in α2-KO cells. Our findings support the concept of a subsarcolemmal space where the α2-isoform coupled with NCX modulates Ca2+-store function and, thereby, CCE.",
keywords = "Calcium homeostasis, Calcium stores, Capacitative calcium influx, Plasma membrane calcium ATPase, Sarco(endo)plasmic reticulum calcium ATPase",
author = "Ron Lynch and Weber, {Craig S.} and Nullmeyer, {Kevin D.} and Moore, {Edwin D W} and Paul, {Richard J.}",
year = "2008",
month = "3",
doi = "10.1152/ajpheart.00855.2007",
language = "English (US)",
volume = "294",
journal = "American Journal of Physiology",
issn = "0363-6143",
publisher = "American Physiological Society",
number = "3",

}

TY - JOUR

T1 - Clearance of store-released Ca2+ by the Na+-Ca 2+ exchanger is diminished in aortic smooth muscle from Na +-K+-ATPase α2-isoform gene-ablated mice

AU - Lynch, Ron

AU - Weber, Craig S.

AU - Nullmeyer, Kevin D.

AU - Moore, Edwin D W

AU - Paul, Richard J.

PY - 2008/3

Y1 - 2008/3

N2 - Two α-isoforms of the Na+-K+-ATPase are expressed in vascular smooth muscle cells (VSMCs). The α1- isoform is proposed to serve a cytosolic housekeeping role, whereas the α2-isoform modulates Ca2+ storage via coupling to the Na+-Ca2+ exchanger (NCX) in a subsarcolemmal compartment. To evaluate the ramifications of this proposed interaction, Ca 2+-store load and the contributions of the primary Ca2+ transporters to Ca2+ clearance were studied in aortic VSMCs from embryonic wild-type (WT) and Na+-K+-ATPase α2-isoform gene-ablated, homozygous null knockout (α2-KO) mice. Ca2+ stores were unloaded by inhibiting the sarco(endo)plasmic reticulum Ca2+-ATPase with cyclopiazonic acid (CPA) in Ca2+-free media to limit Ca2+ influx. Ca2+ clearance by the plasma membrane Ca2+-ATPase (PMCA), NCX, or mitochondria was selectively inhibited. In WT VSMCs, NCX accounted for 90% of the Ca2+ efflux. In α2-KO VSMCs, preferential clearance of store-released Ca2+ by NCX was lost, whereas PMCA activity was increased. Selective inhibition of the α2-isoform (0.5 μM ouabain for 20 min), before treatment with CPA enhanced the store load in VSMCs from WT, but not α2- KO mice. A subsequent analysis of capacitative Ca2+ entry (CCE) indicated that the magnitude of Ca2+ influx was significantly greater in α2-KO cells. Our findings support the concept of a subsarcolemmal space where the α2-isoform coupled with NCX modulates Ca2+-store function and, thereby, CCE.

AB - Two α-isoforms of the Na+-K+-ATPase are expressed in vascular smooth muscle cells (VSMCs). The α1- isoform is proposed to serve a cytosolic housekeeping role, whereas the α2-isoform modulates Ca2+ storage via coupling to the Na+-Ca2+ exchanger (NCX) in a subsarcolemmal compartment. To evaluate the ramifications of this proposed interaction, Ca 2+-store load and the contributions of the primary Ca2+ transporters to Ca2+ clearance were studied in aortic VSMCs from embryonic wild-type (WT) and Na+-K+-ATPase α2-isoform gene-ablated, homozygous null knockout (α2-KO) mice. Ca2+ stores were unloaded by inhibiting the sarco(endo)plasmic reticulum Ca2+-ATPase with cyclopiazonic acid (CPA) in Ca2+-free media to limit Ca2+ influx. Ca2+ clearance by the plasma membrane Ca2+-ATPase (PMCA), NCX, or mitochondria was selectively inhibited. In WT VSMCs, NCX accounted for 90% of the Ca2+ efflux. In α2-KO VSMCs, preferential clearance of store-released Ca2+ by NCX was lost, whereas PMCA activity was increased. Selective inhibition of the α2-isoform (0.5 μM ouabain for 20 min), before treatment with CPA enhanced the store load in VSMCs from WT, but not α2- KO mice. A subsequent analysis of capacitative Ca2+ entry (CCE) indicated that the magnitude of Ca2+ influx was significantly greater in α2-KO cells. Our findings support the concept of a subsarcolemmal space where the α2-isoform coupled with NCX modulates Ca2+-store function and, thereby, CCE.

KW - Calcium homeostasis

KW - Calcium stores

KW - Capacitative calcium influx

KW - Plasma membrane calcium ATPase

KW - Sarco(endo)plasmic reticulum calcium ATPase

UR - http://www.scopus.com/inward/record.url?scp=41549155033&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=41549155033&partnerID=8YFLogxK

U2 - 10.1152/ajpheart.00855.2007

DO - 10.1152/ajpheart.00855.2007

M3 - Article

C2 - 18192219

AN - SCOPUS:41549155033

VL - 294

JO - American Journal of Physiology

JF - American Journal of Physiology

SN - 0363-6143

IS - 3

ER -