Cyr61 and connective tissue growth factor (CTGF), members of a newly identified family of extracellular matrix-associated signaling molecules, are found to mediate cell adhesion, promote cell migration and enhance growth factor-induced cell proliferation in vitro, and induce angiogenesis in vivo. We previously showed that vascular endothelial cell adhesion and migration to Cyr61 and Fisp12 (mouse CTGF) are mediated through integrin ␣ v ␤ 3 . Both Cyr61 and Fisp12/mCTGF are present in normal blood vessel walls, and it has been demonstrated that CTGF is overexpressed in advanced atherosclerotic lesions. In the present study, we examined whether Cyr61 and Fisp12/mCTGF could serve as substrates for platelet adhesion. Agonist (ADP, thrombin, or U46619)-stimulated but not resting platelets adhered to both Cyr61 and Fisp12/mCTGF, and this process was completely inhibited by prostaglandin I 2 , which prevents platelet activation. The specificity of Cyr61-and Fisp12/mCTGF-mediated platelet adhesion was demonstrated by specific inhibition of this process with polyclonal anti-Cyr61 and anti-Fisp12/mCTGF antibodies, respectively. The adhesion of ADP-activated platelets to both proteins was divalent cation-dependent and was blocked by RGDS, HHLGGAKQAGDV, or echistatin, but not by RGES. Furthermore, this process was specifically inhibited by the monoclonal antibody AP-2 (anti-␣ IIb ␤ 3 ), but not by LM609 (anti-␣ v ␤ 3 ), indicating that the interaction is mediated through integrin ␣ IIb ␤ 3 . In a solid phase binding assay, activated ␣ IIb ␤ 3 , purified by RGD affinity chromatography, bound to immobilized Cyr61 and Fisp12/mCTGF in a dose-dependent and RGD-inhibitable manner. In contrast, unactivated ␣ IIb ␤ 3 failed to bind to either protein. Collectively, these findings identify Cyr61 and Fisp12/mCTGF as two novel activationdependent adhesive ligands for the integrin ␣ IIb ␤ 3 on human platelets, and implicate a functional role for these proteins in hemostasis and thrombosis.

Following platelet aggregation, integrin alpha(IIb)beta(3) becomes associated with the platelet cytoskeleton. The conserved NPLY sequence represents a potential beta-turn motif in the beta(3) cytoplasmic tail and has been suggested to mediate the interaction of beta(3) integrins with talin. In the present study, we performed a double mutation (N744Q/P745A) in the integrin beta(3) subunit to test the functional significance of this beta-turn motif. Chinese hamster ovary cells were co-transfected with cDNA constructs encoding mutant beta(3) and wild type alpha(IIb). Cells expressing either wild type (A5) or mutant (D4) alpha(IIb)beta(3) adhered to fibrinogen; however, as opposed to control A5 cells, adherent D4 cells failed to spread, form focal adhesions, or initiate protein tyrosine phosphorylation. To investigate the role of the NPLY motif in talin binding, we examined the ability of the mutant alpha(IIb)beta(3) to interact with talin in a solid phase binding assay. Both wild type and mutant alpha(IIb)beta(3), purified by RGD affinity chromatography, bound to a similar extent to immobilized talin. Additionally, purified talin failed to interact with peptides containing the AKWDTANNPLYK sequence indicating that the talin binding domain in the integrin beta(3) subunit does not reside in the NPLY motif. In contrast, specific binding of talin to peptides containing the membrane-proximal HDRKEFAKFEEERARAK sequence of the beta(3) cytoplasmic tail was observed, and this interaction was blocked by a recombinant protein fragment corresponding to the 47-kDa N-terminal head domain of talin (rTalin-N). In addition, RGD affinity purified platelet alpha(IIb)beta(3) bound dose-dependently to immobilized rTalin-N, indicating that an integrin-binding site is present in the talin N-terminal head domain. Collectively, these studies demonstrate that the NPLY beta-turn motif regulates post-ligand binding functions of alpha(IIb)beta(3) in a manner independent of talin interaction. Moreover, talin was shown to bind through its N-terminal head domain to the membrane-proximal sequence of the beta(3) cytoplasmic tail.

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Background Postoperative atrial fibrillation (POAF) is the most common complication among patients undergoing cardiac surgery. However, data on the economic burden and resource utilization associated with POAF in Asian population are limited. The present study aimed at estimating medical costs attributable to POAF after cardiac surgery in Thai population. Methods We analysed data from claims database of patients who underwent valve replacement, coronary artery bypass grafting (CABG), or a combination of both procedures at a tertiary-care, academic hospital in Thailand. Multiple linear regressions of log-transformed costs were developed with the occurrence of POAF and preoperative patient characteristics as covariates. After back-transformation to the original scale, costs attributable to POAF were estimated from the mean difference between patients with and without POAF. Results Of 711 patients undergoing cardiac surgery, 241 (30.94%) developed POAF over a median hospitalization of 10 days. Patients with POAF utilized more resources than those without POAF. POAF was an independent predictor and increased cost by 23% in linear regression model. On average, patients with POAF had higher medical costs than those without POAF (269,000 versus 218,999 Thai Baht (THB)) with a mean difference of 50,000 THB (1,667 USD). The difference was observed in patients undergoing isolated valve surgery (47,761 THB (1,592 USD), 95% CI: 39,809–55,712), CABG (50,865 THB (1,696 USD), 95% CI: 37,233–64,496), and a combination of both procedures (72,287 THB (2,410 USD), 95% CI: 49,910–94,405). Conclusions In a single-institution study in Thailand, POAF is associated with increased resource use and medical costs among patients undergoing cardiac surgery. Effective strategies to prevent POAF should be implemented to reduce its economic burden.