CEACAM2 positively regulates integrin α_IIbβ₃-mediated platelet functions

Abstract

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is an Ig-ITIM superfamily member that regulates integrin αIIbβ3 function. We hypothesized that its twin protein, CEACAM2, exerts a similar physiologic role in murine platelets. CEACAM2-deficient mice (Cc2) displayed prolonged tail bleeding times and increased volume of blood loss. Cc2 platelets have moderate integrin αIIbβ3-mediated functional defects with impaired kinetics of platelet spreading on fibrinogen and type I collagen and delayed kinetics in the retraction of fibrin clots in vitro. This functional integrin αIIbβ3 defect could not be attributed to altered integrin αIIbβ3 expression. Cc2 platelets displayed normal 'inside-out' signaling properties as demonstrated by normal agonist-induced binding of soluble fluorescein isothiocyanate (FITC)-fibrinogen and JON/A antibody binding. This data provides direct evidence that disruption of CEACAM2 induces a moderate integrin αIIbβ3-mediated platelet function defect, and that CEACAM2 is essential to maintain a normal integrin αIIbβ3-mediated platelet function.

Ibrutinib, but not zanubrutinib, induces platelet receptor shedding of GPIb-IX-V complex and integrin αIIbβ3 in mice and humans

“…Platelet rich plasma (PRP) and washed human or murine platelets were isolated, and platelet aggregation experiments were performed as previously described. [23][24][25]…”

“…Full blood examination parameters were determined as previously described. [23][24][25] Measurement of aand dense-granule exocytosis…”

“…Tail bleeding time was determined as previously described. 24 Flow cytometry. Washed platelets (50 mL of 100 3 10 9 /L) were preincubated with the PE-conjugated antibodies human CD42a (GPIX), anti-human CD41a (integrin a IIb ), anti-human CD61 (integrin b 3 ), anti-human CD42b (GPIba), anti-human GPVI, or anti-human CD42c (GPIbb); APC-conjugated anti-human CD42d (GPV) antibodies; or FITC-conjugated PAC-1 antibodies.…”

“…The subsequent steps and analysis have been described. [23][24][25] Adhesion under flow conditions. A 6-channel m-Slide VI, with dimensions (0.1 3 1.0 3 17 mm, H 3 W 3 L; Microslides; Ibidi, Martinsried, Germany), was precoated with 500 mg/mL type I fibrillar collagen (Nycomed, Linz, Austria), 50 mg/mL VWF, or 100 mg/mL fibrinogen for 2 hours at 37°C, followed by washing with Tyrode's buffer.…”

ITIM receptors: more than just inhibitors of platelet activation

“…CEACAM1 and CEACAM2 are expressed on a variety of tissues, including platelets (supplemental Figure 1), 66 and get upregulated on the surface of activated platelets, suggesting intracellular pools. 21,22 Findings from KO mouse models showed that both CEACAM1 and CEACAM2 attenuate ITAM receptor-mediated responses, presumably via Shp1 and Shp2, but paradoxically positively regulate integrin-mediated responses, 21,22,83,84 a recurring theme for platelet ITIM-containing receptors. Larger and more stable thrombi after ferric chloride injury in vivo was also demonstrated in CEACAM1-and CEACAM2-deficient mice, indicating that the net functions of CEACAM1 and CEACAM2 is to limit thrombus growth.…”