The involvement of the cytoskeleton in regulating IP3 receptor-mediated internal Ca2+ release in human blood platelets.

✍ Scribed by Lilly Y.W. Bourguignon; Naoko Iida; Hengtao Jin

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 468 KB
• Volume: 17
• Category: Article
• ISSN: 1065-6995
• DOI: 10.1006/cbir.1993.1136

✦ Synopsis

Abstract

In this study we have used saponin to permeabilize platelet membranes in order to test directly the involvement of IP~3~ in regulating internal Ca^2+^ release, and to measure IP~3~ binding to its receptor. Our results indicate that platelet vesicles release Ca^2+^ as early as 3 seconds after IP~3~ addition. Using [^3^H]IP~3~, we have found that platelets contain a single class of high affinity IP~3~ binding sites with a Kd of ∼0.20 (± 0.01) nM. Immuno‐blotting shows that platelets contain a 260 kDa polypeptide which shares immunological cross reactivity with brain IP~3~ receptor. Immunofluorescence staining data indicate that the IP~3~ receptor is preferentially located at the periphery of the platelet plasma membrane. Most importantly, both IP~3~ binding and IP~3~‐induced Ca^2+^ release activities are significantly inhibited by cytochalasin D (a microfilament inhibitor) and colchicine (a microtubule inhibitor). These findings suggest that the cytoskeleton is involved in the regulation of IP~3~ binding and IP~3~ receptor‐mediated Ca^2+^ release during platelet activation.