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Aortic smooth muscle and endothelial plasma membrane Ca2+ pump isoforms are inhibited differently by the extracellular inhibitor caloxin 1b1
- Source :
- American journal of physiology. Cell physiology. 290(5)
- Publication Year :
- 2006
-
Abstract
- Plasma membrane Ca2+pumps (PMCA) that expel Ca2+from cells are encoded by four genes (PMCA1–4). In this study, we show that aortic endothelium and smooth muscle differ in their PMCA isoform mRNA expression: endothelium expressed predominantly PMCA1, and smooth muscle expressed PMCA4 and a lower level of PMCA1. In this study, we report a novel peptide (caloxin 1b1, obtained by screening for binding to extracellular domain 1 of PMCA4), which inhibited PMCA extracellularly, selectively, and had a higher affinity for PMCA4 than PMCA1. It inhibited the PMCA Ca2+-Mg2+-ATPase activity in leaky erythrocyte ghosts (mainly PMCA4) with a Kivalue of 46 ± 5 μM, making it 10× more potent than the previously reported caloxin 2a1. It was isoform selective because it inhibited the PMCA1 Ca2+-Mg2+-ATPase in human embryonic kidney-293 cells with a higher Kivalue (105 ± 11 μM) than for PMCA4. Caloxin 1b1 was selective in that it did not inhibit other ATPases. Because caloxin 1b1 had been selected to bind to an extracellular domain of PMCA, it could be added directly to cells and tissues to examine its effects on smooth muscle and endothelium. In deendothelialized aortic rings, caloxin 1b1 (200 μM) produced a contraction. It also increased the force of contraction produced by a submaximum concentration of phenylephrine. In aortic rings with endothelium intact, precontracted with phenylephrine and relaxed partially with a submaximum concentration of carbachol, caloxin 1b1 increased the force of contraction rather than potentiating the endothelium-dependent relaxation. In cultured cells, caloxin 1b1 increased the cytosolic [Ca2+] more in arterial smooth muscle cells than in endothelial cells. Thus caloxin 1b1 is the first highly selective extracellular PMCA inhibitor that works better on vascular smooth muscle than on endothelium.
- Subjects :
- Gene isoform
Male
Endothelium
Physiology
Calcium-Transporting ATPases
Biology
Rats, Inbred WKY
Muscle, Smooth, Vascular
Structure-Activity Relationship
Smooth muscle
medicine
Extracellular
Ca2 pump
Animals
Humans
Protein Isoforms
Gene
Aorta
Messenger RNA
Dose-Response Relationship, Drug
Cell Membrane
Cell Biology
Cell biology
Rats
medicine.anatomical_structure
Membrane
Biochemistry
Endothelium, Vascular
Peptides
Muscle Contraction
Subjects
Details
- ISSN :
- 03636143
- Volume :
- 290
- Issue :
- 5
- Database :
- OpenAIRE
- Journal :
- American journal of physiology. Cell physiology
- Accession number :
- edsair.doi.dedup.....d637c1c67f7d2ceb440909b057e9bb54