SHIP-2 forms a tetrameric complex with filamin, actin, and GPIb-IX-V: localization of SHIP-2 to the activated platelet actin cytoskeleton

Dyson, JM; Munday, AD; Kong, AM; Huysmans, RD; Matzaris, M; Layton, MJ; Nandurkar, HH; Berndt, MC; Mitchell, CA

Author(s): Dyson, JM; Munday, AD; Kong, AM; Huysmans, RD; Matzaris, M; Layton, MJ; Nandurkar, HH; Berndt, MC; Mitchell, CA;
Details: Publication Year 2003-08-01,Volume 102,Issue #3,Page 940-948
Journal Title: BLOOD
Publication Type: Journal Article
Abstract: The platelet receptor for the von Willebrand factor (VWF) glycoprotein Ib-IX-V (GPIb-IX-V) complex mediates platelet adhesion at sites of vascular injury. The cytoplasmic tail of the GPIbalpha subunit interacts with the actin-binding protein, filamin, anchoring the receptor in the cytoskeleton. In motile cells, the second messenger phosphatidylinositol 3,4,5 trisphosphate (PtdIns(3,4,5)P-3) induces submembraneous actin remodeling. The inositol polyphosphate 5-phosphatase, Src homology 2 domain-containing inositol polyphosphate 5-phosphatase-2 (SHIP-2), hydrolyzes PtdIns(3,4,5)P-3 forming phosphatidylinositol 3,4 bisphosphate (PtdIns(3,4)P-2) and regulates membrane ruffling via complex formation with filamin. In this study we investigate the intracellular location and association of SHIP-2 with filamin, actin, and,the GPIb-IX-V complex in platelets. Immunoprecipitation of SHIP-2 from the Triton-soluble fraction of unstimulated platelets demonstrated association between SHIP-2, filamin, actin, and GPIb-IX-V. SHIP-2 associated with filamin or GPIb-IX-V was active and demonstrated PtdIns(3,4,5)P-3 5-phosphatase activity. Following thrombin or VWF-induced platelet activation, detection of the SHIP-2, filamin, and receptor complex decreased in the Triton-soluble fraction, although in control studies the level of SHIP-2, filamin, or GPIb-IX-V immunoprecipitated by their respective antibodies did not change following platelet activation. In activated platelets spreading on a VWF matrix, SHIP-2 localized intensely with actin at the central actin ring and colocalized with actin and filamin at filopodia and lamellipodia. In spread platelets, GPIb-IX-V localized to the center of the platelet and showed little colocalization with filamin at the plasma membrane. These studies demonstrate a functionally active complex between SHIP-2, filamin, actin, and GPIb-IX-V that may orchestrate the localized hydrolysis of PtdIns(3,4,5)P-3 and thereby regulate cortical and submembraneous actin.
Publisher: AMER SOC HEMATOLOGY
Keywords: VON-WILLEBRAND-FACTOR; INOSITOL-POLYPHOSPHATE 5-PHOSPHATASE; GLYCOPROTEIN IB-ALPHA; PHOSPHOINOSITIDE 3-KINASE; BINDING-PROTEIN; MEMBRANE SKELETON; PHOSPHATIDYLINOSITOL 3-KINASE; CYTOPLASMIC DOMAIN; THROMBUS FORMATION; IDENTIFICATION
Publisher's Version: https://doi.org/10.1182/blood-2002-09-2897
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Creation Date: 2003-08-01 12:00:00