title: ADAP interactions with talin and kindlin promote platelet integrin αIIbβ3 activation and stable fibrinogen binding.
abstract: ADAP is a hematopoietic-restricted adapter protein that promotes integrin activation and is a carrier for other adapter proteins, Src kinase-associated phosphoprotein 1 (SKAP1) and SKAP2. In T lymphocytes, SKAP1 is the ADAP-associated molecule that activates integrins through direct linkages with Rap1 effectors (regulator of cell adhesion and polarization enriched in lymphoid tissues; Rap1-interacting adapter molecule). ADAP also promotes integrin αIIbβ3 activation in platelets, which lack SKAP1, suggesting an ADAP integrin-regulatory pathway different from those in lymphocytes. Here we characterized a novel association between ADAP and 2 essential integrin-β cytoplasmic tail-binding proteins involved in αIIbβ3 activation, talin and kindlin-3. Glutathione S-transferase pull-downs identified distinct regions in ADAP necessary for association with kindlin or talin. ADAP was physically proximal to talin and kindlin-3 in human platelets, as assessed biochemically, and by immunofluorescence microscopy and proximity ligation. Relative to wild-type mouse platelets, ADAP-deficient platelets exhibited reduced co-localization of talin with αIIbβ3, and reduced irreversible fibrinogen binding in response to a protease activated receptor 4 (PAR4) thrombin receptor agonist. When ADAP was heterologously expressed in Chinese hamster ovary cells co-expressing αIIbβ3, talin, PAR1, and kindlin-3, it associated with an αIIbβ3/talin complex and enabled kindlin-3 to promote agonist-dependent ligand binding to αIIbβ3. Thus, ADAP uniquely promotes activation of and irreversible fibrinogen binding to platelet αIIbβ3 through interactions with talin and kindlin-3.
authors: Hematology-Oncology Division, Department of Medicine, University of California, San Diego, La Jolla, CA.
authors: Ana
authors: A
authors: Kasirer-Friede
authors: Hematology-Oncology Division, Department of Medicine, University of California, San Diego, La Jolla, CA.
authors: Jian
authors: J
authors: Kang
authors: Hematology-Oncology Division, Department of Medicine, University of California, San Diego, La Jolla, CA.
authors: Bryan
authors: B
authors: Kahner
authors: Hematology-Oncology Division, Department of Medicine, University of California, San Diego, La Jolla, CA.
authors: Feng
authors: F
authors: Ye
authors: Hematology-Oncology Division, Department of Medicine, University of California, San Diego, La Jolla, CA.
authors: Mark H
authors: MH
authors: Ginsberg
authors: Hematology-Oncology Division, Department of Medicine, University of California, San Diego, La Jolla, CA.
authors: Sanford J
authors: SJ
authors: Shattil
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D001792:Blood Platelets / Q000166:cytology / Q000378:metabolism; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D005340:Fibrinogen / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D009363:Neoplasm Proteins / Q000378:metabolism*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D016608:Talin / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D003598:Cytoskeletal Proteins; C477322:FERMT3 protein, human; C106957:FYB1 protein, human; C491468:Fyb protein, mouse; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D016608:Talin; C527818:kindlin-3 protein, mouse; D005340:Fibrinogen