Inhibition of protein cross-linking in Ca2+-enriched human erythrocytes and activated platelets.

Treatment of human erythrocytes with Ca2+, in the presence of ionophore A23187, causes the formation of high molecular weight (greater than 10(6)) membrane protein polymers. This phenomenon, known to involve cross-linking of essentially all of the band 4.1 and 2.1 (ankyrin) proteins, as well as some spectrin, band 3, and hemoglobin molecules, could be prevented by preincubating the cells with a noncompetitive inhibitor of intrinsic transglutaminase, 2-[3-(diallylamino)propionyl]benzothiophene, at concentrations of about (3-6) X 10(-4) M. The compound also eliminated the proteolytic breakdown of the two major transmembrane proteins band 3 and glycophorin, which would otherwise occur during the Ca2+ loading of fresh human red cells. In addition, the inhibitor effectively blocked the formation of a cross-linked protein polymer in thrombin-activated human platelets.