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Ligation of α 5 β 1 ‐ integrins triggers Ca 2+ sparks in renal vascular smooth muscle cells
Author(s) -
Balasubramanian Lavanya,
Lo C.M.,
Landon C.S.,
Sham J.S.K.,
Yip K.P.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a759
Subject(s) - integrin , ryanodine receptor , fibronectin , chemistry , vascular smooth muscle , endoplasmic reticulum , antibody , intracellular , ligation , receptor , microbiology and biotechnology , biophysics , cell , endocrinology , biochemistry , biology , immunology , smooth muscle
Previously we developed a system using an electromagnet to apply controlled mechanical force to freshly isolated vascular smooth muscle cells (VSMC) tagged with fibronectin‐coated paramagnetic microbeads. We demonstrated that magnetic dragging of fibronectin‐coated beads triggered local subcellular Ca 2+ transients in the form of Ca 2+ sparks in rat renal VSMC. The heterodimeric α 5 β 1 ‐ integrin is the dominant receptor of fibronectin in VSMC. Integrin mediated intracellular signaling requires both occupancy and clustering of integrins. Here we sought to determine whether ligation of integrins using α 5 ‐ or β 1 ‐ integrin specific antibodies (50 μg/ml) induces sparks in freshly isolated renal VSMC. Our observation indicated that α 5 ‐ integrin antibody (HMα5‐1) and β 1 ‐ integrin antibody (Ha2/5) elicited Ca 2+ sparks in 90% of the cells. Antibody specific to β 2 ‐ integrin, which is not expressed in VSMC, did not induce any Ca 2+ sparks. Preincubation with 50 μM ryanodine inhibited the occurrence of sparks induced by α 5 ‐ and β 1 ‐ integrin antibodies. These sparks had 0.9 μm median spatial diameter as indexed by full width at half the maximal fluorescence profile. The median duration of the sparks measured at 50% level of amplitude was 12 msec. We concluded that ligation of α 5 ‐ or β 1 ‐ integrins with antibodies triggers subcellular Ca 2+ signal via ryanodine receptors. Supported by AHA Predoctoral Fellowship