CD44 sensitivity of platelet activation, membrane scrambling and adhesion under high arterial shear rates.
CD44 is required for signalling of macrophage migration inhibitory factor (MIF), an anti-apoptotic pro-inflammatory cytokine. MIF is expressed and released from blood platelets, key players in the orchestration of occlusive vascular disease. Nothing is known about a role of CD44 in the regulation of platelet function. The present study thus explored whether CD44 modifies degranulation (P-selectin exposure), integrin activation, caspase activity, phosphatidylserine exposure on the platelet surface, platelet volume, Orai1 protein abundance and cytosolic Ca(2+)-activity ([Ca2+]i). Platelets from mice lacking CD44 (cd44(-/-)) were compared to platelets from corresponding wild-type mice (cd44(+/+)). In resting platelets, P-selectin abundance, α(IIb)β3 integrin activation, caspase-3 activity and phosphatidylserine exposure were negligible in both genotypes and Orai1 protein abundance, [Ca2+]i, and volume were similar in cd44(-/-) and cd44(+/+) platelets. Platelet degranulation and α(IIb)β3 integrin activation were significantly increased by thrombin (0.02 U/ml), collagen related peptide (CRP, 2 µg/ml and Ca(2+)-store depletion with thapsigargin (1 µM), effects more pronounced in cd44(-/-) than in cd44(+/+) platelets. Thrombin (0.02 U/ml) increased platelet [Ca2+]i, caspase-3 activity, phosphatidylserine exposure and Orai1 surface abundance, effects again significantly stronger in cd44(-/-) than in cd44(+/+) platelets. Thrombin further decreased forward scatter in cd44(-/-) and cd44(+/+) platelets, an effect which tended to be again more pronounced in cd44(-/-) than in cd44(+/+) platelets. Platelet adhesion and in vitro thrombus formation under high arterial shear rates (1,700 s(-1)) were significantly augmented in cd44(-/-) mice. In conclusion, genetic deficiency of CD44 augments activation, apoptosis and pro-thrombotic potential of platelets.
Guilai
G
Liu
Guoxing
G
Liu
Kousi
K
Alzoubi
Madhumita
M
Chatterjee
Britta
B
Walker
Patrick
P
Münzer
Dong
D
Luo
Anja T
AT
Umbach
Bernat
B
Elvira
Hong
H
Chen
Jakob
J
Voelkl
Michael
M
Föller
Tak W
TW
Mak
Oliver
O
Borst
Meinrad
M
Gawaz
Florian Lang, Department of Physiology, University of Tübingen, Gmelinstr. 5, 72076 Tübingen, Germany, Tel.: +49 7071 29-72194, Fax: +49 7071 29-5618, E-mail: florian.lang@uni-tuebingen.de.
Florian
F
Lang
D000818:Animals; D017209:Apoptosis; D001777:Blood Coagulation; D001792:Blood Platelets / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling; D053148:Caspase 3 / Q000378:metabolism; D015550:Cell Degranulation; D002462:Cell Membrane / Q000378:metabolism*; D002712:Chlorides; D004195:Disease Models, Animal; D005260:Female; D005290:Ferric Compounds; D005838:Genotype; D018960:Hyaluronan Receptors / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D008297:Male; D040542:Mechanotransduction, Cellular; D018345:Mice, Knockout; D000071740:ORAI1 Protein; D010641:Phenotype; D010743:Phospholipids / Q000097:blood / Q000378:metabolism*; D010973:Platelet Adhesiveness; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D012039:Regional Blood Flow; D051149:Selenoprotein P / Q000378:metabolism; D013314:Stress, Mechanical; D013917:Thrombin / Q000378:metabolism; D013927:Thrombosis / Q000097:blood / Q000235:genetics / Q000378:metabolism*
D015220:Calcium Channels; C476399:Cd44 protein, mouse; D002712:Chlorides; D005290:Ferric Compounds; D018960:Hyaluronan Receptors; D000071740:ORAI1 Protein; C520430:Orai1 protein, mouse; D010743:Phospholipids; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D051149:Selenoprotein P; D013917:Thrombin; C505409:Casp3 protein, mouse; D053148:Caspase 3; C024555:ferric chloride
CD44; cytosolic Ca2+ concentration; phosphatidylserine translocation; platelet activation; thrombus formation