NCX1 and Ca+2 exchangers in human platelets? A putative role in the thombo-hemorrhagic events associated with Congenital Disorder of Glycosylation

BISTUÉ MILLÓN, MB; SIRAVEGNA, M; SPÉCOLA, N; CHACÓN , S.; DODELSON DE KREMER, R; ELSO DE BERBERIAN, G.; ASTEGGIANO, C

Barcelona

Congreso; 12th International Congress of Inborn Errors of Metabolism; 2013

Congenital Disorders of Glycosylation (CDG) are genetic diseases due to defects in glycoproteins or glycolipids synthesis. The phenotype is multisystemic and thrombus-hemorrhagic events are frequently observed in these patients. In platelets, Ca+2 signaling is necessary to prevent inappropriate thrombus formation. The Na+/Ca2+ (NCX) and Na+/K+-Ca2+ (NCKX) exchangers play a crucial role in controlling cytosolic [Ca2+].  The aim of this report is to contribute to the characterization of these exchangers in human platelets, with special emphasis in CDG patients with thrombus-hemorrhagic events.  Our results demonstrate (i) the expression of NCX and NCKX proteins in human platelets, (ii) NCX1 and NCKX1 45Ca2+-uptake, (iii) heavily N- and O-glycosylated proteins by lectin-affinity chromatography and by Western blot. Proteins were detected after the immunoprecipitation and, with different lectins, after enzymatic deglycosilation. (iv) Lower levels of NCKX1 (n=3; P<0.05) and reduced expression of NCX1 in a PMM2-CDG patient (n=3; P< 0.0001) and (v) a significantly decreased Na+-dependent 45Ca+2 uptake in a PMM2-CDG patient with abnormal platelet aggregation (t-test p< 0.05). Our results demonstrated that both exchangers are glycosylated and that the expression and activity of NCX1 are more dramatically reduced than NCKX1, suggesting a possible role for the abnormal platelet aggregation in CDG patients. CONICET-GI11220090100063/FONCyT/PICT2010-2824.