Impaired "outside-in" integrin alphaIIbbeta3 signaling and thrombus stability in TSSC6-deficient mice.
We investigated the role of the hematopoietic-specific tetraspanin superfamily member, TSSC6, in platelet function using wild-type mice and TSSC6-deficient mice. TSSC6 is expressed on the surface of murine platelets and is up-regulated by thrombin stimulation, indicating an intracellular pool of TSSC6. Immunoprecipitation/Western blot studies reveal a constitutive physical association of TSSC6 with the integrin alpha(IIb)beta(3) complex under strong detergent conditions. In vivo evaluation of hemostasis by tail bleeding revealed increased bleeding time, volume of blood lost, and evidence of tail rebleeds in TSSC6 null mice, indicating unstable hemostasis. Using ex vivo techniques, we showed that TSSC6-deficient platelets exhibited impaired kinetics of clot retraction, platelet aggregation at lower doses of PAR-4, and collagen and platelet spreading on fibrinogen in the presence of normal integrin alpha(IIb)beta(3) expression. TSSC6-deficient platelets showed normal alpha granule secretion, normal "inside-out" integrin alpha(IIb)beta(3) signaling (fluorescein isothiocyanate [FITC]-fibrinogen and JON/A binding), and normal platelet adhesion on fibrinogen. Furthermore, we show that absence of platelet TSSC6 affects the secondary stability of arterial thrombi in vivo upon vascular injury. These data demonstrate that TSSC6 appears to regulate integrin alpha(IIb)beta(3) "outside-in" signaling events in platelets and is necessary for stability of arterial thrombi in vivo.
Goschnick
Matt W
MW
Burnet Institute/Austin Research Institute, Studley Road, Heidelberg, Victoria 3084, Australia.
Lau
Lai-Man
LM
Wee
Janet L
JL
Liu
Yong S
YS
Hogarth
P Mark
PM
Robb
Lorraine M
LM
Hickey
Michael J
MJ
Wright
Mark D
MD
Jackson
Denise E
DE
D000818:Animals; D001792:Blood Platelets / Q000502:physiology*; D003018:Clot Retraction / Q000502:physiology; D006487:Hemostasis; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000172:deficiency* / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010973:Platelet Adhesiveness / Q000502:physiology; D010974:Platelet Aggregation / Q000502:physiology; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism*; D015398:Signal Transduction; D013927:Thrombosis / Q000097:blood; D059470:Tetraspanins
D008565:Membrane Proteins; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; C417909:Tspan32 protein, mouse; D059470:Tetraspanins